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1973 Seasonal Biomass, Abundance, and Distribution of Estuarine Dependent Fishes in the Caminada Bay System of Louisiana. Paul Robert Wagner Louisiana State University and Agricultural & Mechanical College
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Recommended Citation Wagner, Paul Robert, "Seasonal Biomass, Abundance, and Distribution of Estuarine Dependent Fishes in the Caminada Bay System of Louisiana." (1973). LSU Historical Dissertations and Theses. 2437. https://digitalcommons.lsu.edu/gradschool_disstheses/2437
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Xerox University Microfilms 300 North Zeeb Road A nn Arbor, Michigan 4B106 73-27,879 WAGNER, Paul Robert, 1947- SEASONAL BICMASS, ABUNDANCE, AND DISTRIBUTION OF ESTUARINE DEPENDENT FISHES IN THE CAMINADA BAY SYSTEM OF LOUISIANA.
The Louisiana State University and Agricultural and Mechanical College, Ph.D., 1973 Ecology
University Microfilms, A XEROX Com pany, Ann Arbor, Michigan <
THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED. Seasonal Biomass, Abundance, and Distribution of Estuarine Dependent Fishes in the Caminada Bay System of Louisiana
A Dissertation
Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy
in
The Department of Marine Sciences
by Paul Robert Wagner B.S., Tulane University, 1968 M.S., Tulane University, 1970 May, 1973 ACKNOWLEDGEMENTS
I would like to express my appreciation to my advisor, Dr.
Harold Loesch, for providing inspiration and guidance in both field work and the writing of this dissertation. I also wish to thank the other members of my graduate committee, Dr. Ted Ford,
Dr. William G. Smith, Dr. Frank Truesdale and Dr. Dudley Culley for helpful advice and support throughout ttry entire graduate pro gram.
Logistical support was provided in the way of a base camp at
Grand Isle where boats, nets and equipment were kept. I appreciate the help of Rodney Adams, Edwin Bishop and James Blackmon in th is capacity.
Assistance in the collection of fishes was provided by Harold
Loesch, John Day, Gill Smith, Arthur Crowe, Steve Loesch, Jon
Loesch, Steve Verret, Robin Kuckyr, Jim Bishop and Richard Day.
Thanks are due to each of them.
John Day, Becky Horn, and Mrs. A lice Dunn were p a rtic u la rly helpful in preparing the figures. I would also like to express my appreciation to Mrs. Joan Myers for typing the manuscript.
Special recognition is due ray mother and father, Helene and
Paul E. Wagner, for their confidence and encouragement.
This investigation was sponsored by Louisiana State University's
Office of Sea Grant Development. LSU's Sea Grant Program is a part of the national Sea Grant Program, which is maintained by the National
Oceanic and Atmospheric Administration of the U. S. Department of
Commerce.
i i TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS...... i i
LIST OF TABLES...... v
LIST OF FIG U R ES...... v i i
ABSTRACT ...... x
INTRODUCTION...... 1
Factors Affecting Fish Populations ...... 1 Louisiana Estuaries ...... 1 Estuarine Fisheries - Exploited Yet Not Understood . . . 2 O b je c tiv e s ...... 3 Previous Work ...... 4
DESCRIPTION OF THE STUDY AREA...... 12
Caminada B a y ...... ' ...... 12 Description of Sampling Stations ...... 14
MATERIALS AND. METHODS...... 19
Use and Measurements of Sampling Gear...... 19 Station Sampling Frequency...... 22 Hydrographic Parameters...... 23 Processing of Samples and Laboratory Procedure ...... 23 Analysis of .Fie Id D ata ...... 26 . Length-Frequency Distributions...... 26 Length-Weight Relationship...... 26 Procedure' Used in Calculating Fish Production . . . 26
RESULTS AND DISCUSSION...... 30
Major Physiocochemical Conditions ...... 30 Temperature...... 30 Salinity...... 34 Caminada Bay Fish Population ...... 39 Seasonal Biomass and Abundance ...... 41 . Trawl Biomass...... 41 . Trammel Net Biomass ^ '46 Seine Biomass ...... 47 T otal Biomass Taken w ith Combined Gear. .... 51 Factors Influencing Seasonal Biomass and Abundance ...... 53 Temperature ...... 53
i i i Page
Salinity and Species Diversity ...... 56 Food A v a i l a b i l i t y ...... 57 Areal Biomass and Abundance ...... 58 In d iv id u al S tatio n Biomass and Abundance ...... 58 Individual Station Biomass and Abundance - Summary ...... 66 Importance of Nearshore Zone and Marsh-Water I n t e r f a c e ...... 72 Biomass, Abundance and Distribution of Dominant S p e c i e s...... 75 Anchoa m itchilli ...... 75 B revoortia patronus...... 79 Leiostomus xanthurus ...... 83 Micropogon undulatus ...... 86 Arius felis ...... 91 Biomass, Abundance and Distribution of Less Abundant and Rare Species...... 93 Trophic Level Biomass ...... 108 Seasonal Movements and M ig ra tio n s...... 110 Categorization of Fishes ...... 114 Seasonal and Areal Species Composition...... 116 Gear Selectivity ...... 127 Age and Growth of the Atlantic Croaker ...... 130 E stim ate of Growth from Length-Frequency Distribution ...... 132 Scale Analysis ...... 135 Length-Weight Relationship ...... 139 Fish Production ...... 142 Direct Estimate of Age Class 0 Atlantic Croaker Production ...... 146 Allen Graphical Method...... 146 Ricker Numerical Method ...... 150 Estimate of Total Fish Production Based on Atlantic Croaker Production ...... 151 Indirect Estimate of Potential Fish Production Based on Primary Productivity Data ...... 156
CONCLUSIONS...... 159
REFERENCES CITED ...... 168
APPENDIX...... 178
VITA ...... 193
iv LIST OF TABLES
Table Page
1. Sampling S chedule...... 24
2. Summary of Physical Data - Caminada Bay A rea ...... 31
3. Water Temperatures °C in the Caminada Bay Area March 1971 - June 1972 ...... 33
4. Salinities °/oo in the Caminada Bay Area March 1971 - June 1972 ...... 38 2 5. Seasonal Biomass of Fishes (g/m Wet Weight) Available to Fishing Gear at Each Station ...... 68
6. Summary of Station Biomass, Abundance and Species Composition D ata...... 70
7. Numerical Abundance and Seasonal Biomass of the Most Frequently Caught Species Taken at All S ta tio n s w ith Combined Gear ...... 76
8. Total Number and Biomass, Length Range, Maximum and Minimum S a lin itie s and Temperatures, Location and Method of Capture of All Species Taken in the Caminada Bay Area March 1971 - June 1972 ...... 94
9. Mean Standing Crop Biomass of Fishes of Each Trophic L evel...... 109
10. Taxonomic Check L is t, Trophic Level, and Category of Fishes of the Caminada Bay System ...... 117
11. Species Taken Exclusively During Each Season and A ll Y e a r ...... 124
12. Species Taken Only at Certain Stations and At All S t a t i o n s ...... 125
13. Selectivity of the Three Types of Gear ...... 128
14. Species Taken with Only One Type of Gear and By All Gear . . . 129
15. Age-Length Relationship of Atlantic Croaker from Previous Studies Along the Atlantic and Gulf Coasts and This Study ...... 131
v Table Page
16. Estimate of Age Class 0 Croaker Growth Rate Derived from Length-Frequency Data ...... 136
17. Length-Frequency Distribution of Age Class 0 Atlantic Croakers from July 1971 to June 1972 ...... 137
18. Length-weight relationship, Micropogon undulatus, Caminada Bay Area, May 1971 - April 1972 ...... 140
19. Estimates of Standing Crop Biomass in Estuarine and Marine Ecosystems ...... 143
20. Atlantic Croaker Production (Age Class 0) in the Caminada Bay System (1971-2) Derived from Allen's Graphical Method...... 148
21. Atlantic Croaker Production (Age Class 0) in the Caminada Bay System (1971-2) Derived from Ricker's Numerical Method ...... 152
22. Estimates of Fish Production in Estuarine and Marine Ecosystems Based on Field Measurements ...... 155
23. Potential Annual Fish Production in the Caminada Bay System Based on Primary Productivity D ata ...... 158
24. Analysis of Variance, Biomass and Numbers of Fish Taken with 16 Foot Trawl ...... 178«t
v i LIST OF FIGURES
Figure Page
1. Map of Caminada Bay System and Sampling Stations...... 16
2. Mean Surface Water Temperatures in the Caminada Bay System from March 1971 - June 1972...... 32
3. Monthly Mean and Range of Water Temperatures Taken from Continuous Recorder at Grand Terre Marine Laboratory, March 1971 - June 1972 ...... 35
4. Salinities (°/oo) at Each Station from March 1971 - June 1972 ...... 37
5. Biomass of Trawl Caught Fishes in the Caminada Bay System March 1971 - June 1972 ...... 42
6. Biomass of Fishes Taken w ith 300 f t . Trammel Net in the Caminada Bay System April 1971 - June 1972 ...... 48
7. Biomass of Fishes Taken with 75 ft. Bag Seine in the Caminada Bay System May 1971 - June 1972 ...... 50
8. T otal Biomass and Number of Fish Taken with Combined Gear at All Stations March 1971 - June 1972 ...... 52
9. Total Biomass of Fish Taken with Combined Gear in Relation to Seasonal Mean Water Temperature and Mean Species D iv e rsity March 1971 - June 1972 ...... 54
10. Seasonal Biomass of Trawl Caught Fishes in Relation to Seasonal Food Biomass (1971) ...... 59
11. Seasonal Biomass of Trawl Caught Fishes in Relation to Seasonal Production of Organic Detritus (1971) . . 60
12. Biomass and Number of Fish Taken with 75 ft. Bag Seine a t S ta tio n 0, May 1971 - June 1972 ...... 179
13. Biomass and Number of Fish Taken with 16 ft. Trawl a t S ta tio n 1, March 1971 - June 1972 ...... 180
14. Biomass and Number of Fish Taken with 75 ft. Bag Seine at Station 1, May 1971 - June 1972 ...... 181
15. Biomass and Number of Fish Taken with 16 ft. Trawl a t S ta tio n 2, March 1971 - June 1972 ...... 182
v i i Figure Page
16. Biomass and Number of Fish Taken with 75 ft. Bag Seine at Station 2, June 1971 - May 1972 ...... 183
17. Biomass and Number of Fish Taken w ith 300 f t . Trammel Net a t S ta tio n 2, A pril 1971 - May 1972 ...... 184
18. Biomass and Number of Fish Taken w ith 16 f t . Trawl at Station 3, March 1971 - June 1972 ...... 185
19. Biomass and Number of Fish Taken with 75 ft. Bag Seine at Station 3, May 1971 - June 1972 ...... 186
20. Biomass and Number of Fish Taken with 16 ft. Trawl at Station 4, March 1971 - June 1972 ...... 187
21. Biomass and Number of Fish Taken w ith 300 f t . Trammel Net at Station 4, May 1971 - June 1972 ...... 188
22. Biomass and Number of Fish Taken with 16 ft. Trawl a t S ta tio n 5, March 1971 - June 1972 ...... 189
23. Biomass and Number of Fish Taken with 75 ft. Bag Seine at Station 5, May 1971 - June 1972 ...... 190
. 24. Biomass and Number of Fish Taken with 16 ft. Trawl a t S ta tio n 6, March 1971 - June 1972 ...... 191
25. Biomass and Number of Fish Taken w ith 300 f t . Trammel Net at Station 6, June 1971 - May 1972 ...... 192
26. Seasonal Biomass and Number of Anchoa m itchilli Taken with Combined Gear at All Stations, March 1971 - June 1972 ...... 78
27. Seasonal Biomass and Number of Brevoortia patronus Taken w ith Combined Gear at A ll S ta tio n s , March 1971 - June 1 9 7 2 ...... 80
28. Seasonal Biomass and Number of Leiostomus xanthurus Taken with Combined Gear at All Stations, March 1971 - June 1972 ...... 84
29. Seasonal Production, Biomass and Number of Micropogon undulatus Taken with Combined Gear at All Stations, July 1971 - June 1972 ...... 87
30. Seasonal Biomass and Number of Arius fells Taken with Combined Gear at All Stations, March 1971 - June 1972 ...... 92
v i i i Figure Page
31. Seasonal Length-Frequency Distributions of Micropogon undulatus Taken in the Caminada Bay System w ith Combined Gear, July 1971 - June 1972 ...... 133
32. Length-Weight Relationship, Micropogon undulatus, Caminada Bay System, May 1971 - A p ril 1972 ...... 141
33. Allen Curve of Age Class 0 Micropogon undulatus Production, Caminada Bay System, 1971-2 ...... 147
ix ABSTRACT
This study was the first attempt at measuring fish production
quantitatively in the coastal waters of Louisiana. Very little quan
titative data have previously been collected on estuarine fish popula
tions. Results indicate a higher production rate than any previously
reported in estuaries. Seasonal and areal fish biomass, numerical
abundance, species composition, and distribution were also determined.
Factors responsible for seasonal fluctuations were discussed. Esti
mates of biomass and abundance were minimal due to gear selectivity aid sampling bias. Temperature was a dominant factor affecting biomass,
abundance, distribution and production in the bay. Seven stations in
the Caminada Bay system were sampled every three weeks for 16 months
with otter trawl, bag seine and trammel net.
A total of 100 species of fishes were taken in this study. They
were classified into five categories based on-their degree of estuarine
dependency. The majority of fishes were seasonal migrants utilizing the
estuary as spawning, feeding or nursery areas. At least five separate
migrations which occurred throughout the year were discernible.
Two peaks in biomass occurred, one in April and another in August.
Minimum biomass occurred from November to February. Biomass was h ig h est
in the more saline areas of the bay. The shallow nearshore zone includ
ing the shorelines of bays, channels and tidal ponds supported much
higher biomass than deeper water areas.
Numerical abundance was highest in March when peak numbers of
larval and postlarval fishes were moving inshore and lowest in November.
x Numerical abundance generally Increased toward lower salinities due to larger numbers of juvenile fishes in the upper bay.
The dominant species in terms of total number and weight were
Anchoa m itchilli, Brevoortla patronus. Leiostomus xanthurus,. MicropoRon undulatus and Arius fells. These five species comprised 83% of the total number and 41% of the total weight of fish taken. The other 95 species comprising 17% of the total number and 59% of the total weight included
22 species that were taken only once. The majority of fishes taken were mid carnivores.
There was much variation in seasonal and areal species occur rence. Generally, species diversity was highest from July to October and lowest from November to February. Fewer species were taken in the lower salinities of the upper bay.
Gear selectivity was evaluated. Of the three gears used, the bag seine was most effective. It captured the greatest weight of fish, highest mean biomass in grams per square meter, greatest mean number per square meter and highest number of species.
Growth rates were determined for the Atlantic croaker. A length of 140 to 150 millimeters total length is reached at the end of the first year with an average rate of growth of 12 millimeters per month.
Estimates of actual and potential fish production indicated the
Caminada estuary produced more fish per unit area than any estuary previously rep o rted . A minimum of 72.8 grams/square m eter/year wet weight or 647.9 pounds/acre/year wet weight was produced which was 42% of the maximum potential production available from primary production.
The estimated efficiency of conversion of net primary production into secondary fish production was 1.4%
x i I . INTRODUCTION
Factors Affecting Fish Populations
Seasonal biological rhythms were among the first phenomena that man
noted about the natural environment. Such rhythms in the ecological
life history aspects of animals are brought about by a complex combin
ation of physical, chemical, and biological factors. This is especially
true for the fishes inhabiting our coastal estuaries. Estuaries are by
nature characterized by a dynamic variability found in few other natural
ecosystems. There is a constant interaction between the physical
factors of wind, tidal flushing, rainfall, fresh water from river run
off and temperature; chemical factors of salinity and nutrient concen
tration; and the biological factors of spawning, migration, growth,
biomass, and production. Probably the most important factor influencing
the biological activities of estuarine fishes is temperature (Gunter,
1945). Other factors influencing population levels are natural mortality,
fishing'mortality (yield to man), interspecific competition, food
production through the detrital food web, and the type of benthic
s u b s tra te .
Louisiana Estuaries
The Louisiana marshes are among the largest (Chabreck, 1970) and
most productive in the world (Gunter, 1963). The major reasons for
this high productivity are the input of nutrients and freshwater from
the Mississippi River, a subtropical climate regime, abundant rainfall,
cycling of nutrients, minerals, and organic detritus by tidal flushing,
1 shallow depths allowing for maximum year-round photosynthesis by three
types of primary producers (benthic algae, phytoplankton, and marsh macrophytes), abundant food supplies in the form of detritus, and a high ratio of shoreline to water interface (Day jet a l., 1973). There are approximately 4.2 million acres of coastal marshes in Louisiana
(Chabreck, 1970) comprising nearly 75% of the entire marshlands fringing the Gulf of Mexico and more than half of the total coastal marsh area of the contiguous United States (Chapman, 1971). Because of the vastness of this estuarine area and its high apparent productivity, Louisiana has
led the nation in recent years in commercial fishery, harvest. Lindall et a l. (1971) reported the average annual harvest (1963-67) of the nine major commercial fisheries of Louisiana estuaries to be 842.4 million pounds worth $43.5 million. He also stated that the Barataria-Caminada estuarine system produced the highest fishery harvest of all Louisiana estuaries accounting for 44% of the total state yield. In 1970, Louisi ana led all states in volume of catch, landing 1.1 billion pounds worth
$62.0 m illio n (U.S. Department of Commerce, 1970). In 1971, Louisiana again led all states in volume of catch, landing 1.3 billion pounds worth $72.6 million (U.S. Department of Commerce, 1971). Gunter (1963)
termed the area between Pascagoula, Mississippi, and Port Arthur, Texas, as the "Fertile Fisheries Crescent" and stated that, based on fishery harvest, this area was the most productive fisheries region on earth.
Estuarine Fisheries - Exploited Yet Not Understood
Louisiana's estuarine fisheries are well known for their value and commercial importance. However, many aspects of the life history of even the most common fishes are unknown. L ittle is known'about the seasonal quantity of fish in a unit area. Gunter (1967} states that quantitative information on the most fertile part of the Gulf coast is practically nil. Most previous studies in estuaries have been quali tative and have not dealt with biomass or production. Fish inhabit estuaries in great abundance, but the factors responsible for this abundance are not fully understood. Species composition and seasonal distribution of the fish fauna in Louisiana estuaries have been studied but not adequately determined. There are very few estimates of estuarine fish production and none in Louisiana. It is difficult to quantitate estuarine fish populations because they are constantly changing. Bio mass (weight), numerical abundance and species composition vary with salinity, depth, benthic habitat preference, temperature, and probably other unknown fa c to rs . Compounding these e f f e c ts are the problems involved with gear selectivity and sampling bias.
O bjectives
Five objectives were established for this study based on the fore going lack of knowledge.
1. To determine seasonal and areal biomass, numerical abundance, species composition, and distribution of fishes in the Caminada Bay system over a yearly cycle in different habitats.
2. To obtain two quantitative estimates of fish production based on first, seasonal numerical abundance, biomass and corresponding increase in mean weight per unit time (the Allen graphical method, 1951, and the Ricker numerical method, 1946) and secondly, the indirect esti mation by calculation from primary production data.
3. To determine age and growth rates of the Atlantic croaker, Micropogon undulatus.
4. To evaluate effectiveness of three different types of col
lecting gear due to their selectivity in capturing certain sizes and
species of fish.
5. To determine the relationship of biomass, abundance and
distribution of estuarine-dependent fishes to temperature and salinity.
Previous Work
A review of the literature indicates that the vast majority of
estuarine ecological studies have been of the qualitative general survey . i type or of life history aspects of an individual species dealing with
age and growth, fecundity, spawning, food habits, movements and the like.
Very .few have dealt with biomass and even fewer with fish production.
This is partially attributable to the difficulty in obtaining quantita
tive estimates of estuarine fishes. Estuarine fish populations are not
confined to a given area and are present only seasonally. There has
also been very little work done on gear selectivity. Sampling gear bias
often has as great an effect on the catch taken as the actual abundance
of fishes and it is at times difficult to determine if variations in
catch are due to actual seasonal fluctuations or gear selectivity.
There is an abundance of general qualitative survey studies along
the Gulf Coast. Louisiana studies will be emphasized while those in
other areas will only be referred to briefly. This is by no means a
complete listing. Florida studies include those of Joseph and Yerger
(1956), Kilby (1955), Reid (1954), Springer and Woodburn (1960), Sykes
and Finucane (1966), and Zilberberg (1966). These studies have dealt
with seasonal abundance, distribution and species composition. In Alabama, studies by Boschung (1957) and Swingle (1971) deserve mention.
Both studies are ecological life history and distribution studies.
Mississippi workers include Ford (1958) and Franks et: al. (1972). These studies dealt with communities of fishes in different habitats. In Texas survey studies include those of Gunter (1945), Hoese (1965), and Pearson
(1929). Gunter (1945) related distribution of coastal fishes to salin ity. Hoese (1965) determined spawning of marine fishes in the Port
Aransas area by distribution of young and larvae. Pearson (1929) studied the life history of commercially important sciaenids in Texas. Perhaps the most extensive work throughout the Gulf Coast estuaries has been done by Gunter (1938, 1941, 1945, and many other papers). Gunter established many present concepts of Gulf estuarine ecology (e.g. Gunter, 1967).
In the St. Bernard delta area of Louisiana, Fontenot and Rogillio
(1970) correlated the catch of various sciaenids to salinity, temperature and tidal stage. They found little correlation between salinity and catch but a direct correlation between temperature and catch. Rounsefell
(1964) summarized data on the area through which the Mississippi River-
Gulf Outlet navigation canal was dug. He analyzed salinity tolerances of fishes and predicted what effect increased salinity caused by channel construction would have on fish distribution. In the Lake Ponchartrain area, Suttkus (1954) studied the seasonal movements and growth of the
Atlantic croaker. In other studies Suttkus (1956, 1958, 1961 and 1962) has reported on the early life history, distribution, fecundity, and repr duction of the Gulf menhaden and the fecundity of the Spotted seatrout.
Kelley (1965) studied a brackish to fresh water deltaic marsh near the mouth of the Mississippi River. He collected 69 species of which the Centrarchidae was the dominant freshwater family and the Sciaenidae the most abundant marine family. Blue catfish, Ictalurus furcatus, was the dominant species.
In the Barataria-Caminada Bay region, studies have been done by
Behre (1950), Dawson (1966), Fox and Mock (1968), Gunter (1938), Forman
(1968), Irwin (1969), Bellinger and Avault (1970), and Dunham (1972).
Behre (1950) listed 113 species of fishes from the Grand Isle area as a result of a faunistic inventory by the Louisiana State University marine laboratory from 1928 to 1946. Dawson (1966) added 40 new species of offshore fishes to the list of known marine fauna of the
Grand Isle area as a result of a 16 month ecological study in Gulf waters. Fox and Mock (1968) studied the seasonal occurrence of 72 species of fishes in two shoreline habitats in Barataria Bay using a
100 foot beach seine. They utilized two stations, one in the northern part of the bay in low salinity and the other in a more saline area near Grand Terre Island. The most abundant species in both habitats was the bay anchovy, Anchoa m itchilli, making up over 98% of the total catch along with Micropogon undulatus and Brevoortia patronus. Gunter
(1938) did a deeper water trawl study of Barataria Bay using 5 stations from the upper bay to several miles offshore. Collections were made with a 35 foot otter trawl with emphasis on seasonal trends in abundance and species composition. The Atlantic croaker, Micropogon undulatus, was found to be the most abundant fish in this study. It should be noted that the different dominants in this work and that of Fox and
Mock was probably due largely to gear selectivity. Forman (1968) studied ecological aspects of cyprinodont fishes on Grand Terre Island, a barrier island at the entrance of Barataria Bay. Irwin (unpublished)
compiled a checklist of 238 species of fishes within a 20 mile radius
of Grand Isle by consulting past literature, charter boat captains,
sport fishermen, cat-food plants, research collections and personal
sampling trips. Bellinger and Avault (1970) studied seasonal occurrence
of ju v en ile F lo rid a pompano in the s u rf a t Grand I s le and found them most abundant from May through October. Dunham (1972) conducted a
study of the commercially important estuarine dependent industrial fishes in the Barataria and Caminada Bay area. He found that Atlantic
croakers comprised over 65% of the total industrial bottomfish catch off Louisiana. Frank Truesdale (personal communication) is sampling plankton and larval fish populations in Caminada Pass with beam trawl, plankton net and bottom sled. Emphasis is on seasonal and diurnal movements and abundance. None of the above studies have dealt with fish production.
Farther west along the Louisiana coast, seasonal distribution studies have been conducted in Vermilion Bay by Dugas (1970), Norden
(1966) and Perret (1966). Herke (1971) documented the importance of
semi-impounded tidal marshes as nursery areas for fishes and crustaceans
in the Biloxi marsh and Marsh Island areas. Theses by Holloway (1969) and Weaver (1969) in the Marsh Island estuary have delt with marsh nursery usage by fishes. A coast-wise estuarine inventory study was completed in 1969 by the Louisiana Wild Life and Fisheries Commission.
Six major hydrologic units were studied and 100 species of fishes were
collected using 16 foot otter trawls and 100 foot beach seines. In
order of abundance the major species taken were Anchoa m itchilli,
Micropogon undulatus, Brevoortia patronus, Polydactylus octonemus. LeiostomuB xanthurus, Artus fells and Cynosclon arenarius. High off
shore fish yield derived from Louisiana coastal estuaries was documented
in a study by Moore, Brusher, and Trent (1970) in which monthly shrimp
trawl collections were made between the Mississippi River Delta and the
Mexican border. They found catches were generally two to five times
greater off Louisiana than off Texas.
There have also been a considerable number of stu d ies done on in d i
vidual life history aspects of particular estuarine species. Some of
those dealing with age and growth, spawning, distribution and abundance
include Arnold (1958), Bearden (1964), Garwood (1967), Hansen (1969),
Haven (1957 and 1959), Nelson (1969), Parker (1971), Roithmayr (1963),
Simmons and Breuer (1962), Sundararaj (1960), Suttkus (1954, 1956, 1958),
and Wallace (1941). Studies dealing solely with food habits and trophic
structure are those of Boothby (1969), Carr (1971), Darnell (1958), June
and Carlson (1971), Lambou (1952), Odum (1971), Reid £t al. (1956) and
Roelofs (1954).
Fish production studies have been conducted primarily in fresh waters. These studies have for the most part been in smaller water bodies such as small lakes, ponds, and streams (Wiley, 1972) in which
a confined population of fish can be studied. Freshwater productivity
studies have been carried out by Chapman (1965), Gerking (1962),
Hamilton (1969), Hopkins (1971), Mathews (1971), Mann (1969), Ricker
(1946) and Car lander (1955). Mathews' 1971 study pointed out the
significant fact that much productivity occurs in young and juvenile
stages of young of the'year fishes which are subject to high mortality.
He found that among four species of River Thames fishes, production during the first year of life was 66 to 73% of the total cohort production. Marine productivity studies have centered around reef studies (Bardach, 1959), tidal salt ponds (Hall and Woodwell, 1971) and production in upwelling regions (Cushing, 1971). Bardach worked on a Bermuda reef and arrived at an estimate of 153.4 lbs. per acre per year total fish production by periodic visual observation by divers of the standing crop of fishes present on the reef. He collected samples of the fish present for weight determinations and by appropri ate calculation, estimated fish production. Hall and Woodwell (1971) arrived at an estimate of 60 g/m^/yr or 534 lb/acre/yr fish production utilizing a drop net in Flax Fond, Long Island, Mew York. Cushing arrived at fish production estimates by calculation of energy transfer from the primary producers. He assumed there was a 10% efficiency coefficient between each trophic level. Other studies have used the same method of calculation: that of indirect estimation from primary productivity data. To get such an estimate, the trophic level and trans fer efficiency factor must be known. Ryther (1969) and Schaefer (1965) used this method to arrive at estimates of potential world fishery yield based on extrapolation from the known primary produc ion of various types of marine environments. Rounsefell (1971) modified the estimates of these authors by recalculating the area of different marine habitats and harvestable biomass. Wiley (1972), using the method of Ryther (1969), estimated the potential annual production of fish in the Patuxent River, Maryland. He arrived at annual estimates for herbivores from 29.2 to 94.9 g carbon/m^, for first stage carnivores 2 from 2.9 to 19.0 g c/m , and for second stage carnivores from .29 to 10
3.8 g c/m^ depending on what ecological efficiency factor was used. Clark
(1946) discussed the production dynamics on the A tlantic's George's
Bank.
Studies on the biomass of fishes In Gulf estuaries have been done
In Texas by Jones (1963) utilizing a helicopter borne purse net,
McFarland (1963) using a large beach seine, Moseley and Copeland (1969) with a portable purse net and Hoese and Jones (1963) using a portable drop-net quadrat. Helller (1962) was the first to actually measure
fish production In an estuarine area rather than get an Indirect esti mation from primary productivity data. Helller used a drop net quadrat
In the shallow waters of the Laguna Madre of Texas and obtained seasonal biomass estimates ranging from 2.0 g/m^ in winter to 37.8 g/m^ in
summer. He calcu lated production by m u ltiplying the number of fis h taken per month times the monthly growth rate as taken from length
frequency histograms. Annual fish production was calculated to be 15.4
g/m^ wet weight. Copeland (1965) used a tide trap in the Aransas Pass
Inlet in Texas as a basis for a computation of 57.6 g/m^/yr or 513
lbs/acre/yr fish and invertebrate production (wet weight). A tabula
tion of studies done on biomass and fish production may be found in
the section on fish production.
In Louisiana, no studies have been done on estuarine fish pro
duction and only two or three on biomass. Kelley (1965) found standing
crops of fishes in the marshes on the Delta Wildlife Refuge at the
mouth of the Mississippi River from 1.22 to 258.82 pounds per acre.
Forman (unpublished) is conducting seasonal biomass studies in Lake
Grande Ecaille. Lindall et al. (1971) calculated rough indices of production In nine hydrologic units of Louisiana by considering the
Inshore and offshore harvest of the nine major commercial fisheries and acres of nursery grounds within each unit. It should be pointed out that Llndall's data represents fishery yield and not total fish production. He found the Baratarla-Caminada Bay system produced a yield of 1,092 lbs/acre which is the highest reported yield that I know of. I I . DESCRIPTION OF THE STUDY AREA
Caminada Bay
Caminada Bay is a deltaic estuary formed approximately 900 years
" ago (Gagliano and van Beek, 1970) by the shifting deltaic plain of the
Mississippi River. Deltaic sedimentation is no longer occurring in
this region due to leveeing of the river and shifting of the deltaic
lobe to its present position east of the bay. As a result, a series
of abandoned river distributaries run through the region in a northwest
to southeast direction. Caminada Bay, with an overall area of 5,663
hectares averages 1.2 to 1.5 meters in depth and attains a maximum depth
of 10.6 meters in Caminada Pass (Barrett, 1970). The bay is bordered
on the northwest by a complex network of marshes, bayous and smaller
bays, on the northeast by larger Barataria Bay, and on the south by
Caminada Pass, Grand Isle and the Gulf of Mexico.
The bay is characterized by peripheral marshes of a rather uniform
elevation of about one foot above mean Gulf level, diurnal tides with
a small seimdiurnal component both of which are strongly influenced by
winds, high levels of turbidity, and rapid fluctuations in temperature
and salinity. It has an essentially flat bottom topography composed pri
marily of clayey silt (Barrett, 1971), silty sand, and organic detritus,
and an average annual rainfall of about 60 inches (Day et a l., 1972).
Caminada and Barataria Bay form the southern end of a triangular shaped
interdistributary basin system, 64 km west of the mouth of the
Mississippi River and 16 km east of Bayou Lafourche, a former river
12 13 distributary. Freshwater swamps and marshes in the northern part of this basin extend inland for more than 96 km before reaching the levee of the active channel of the Mississippi River. This broad expanse of marshes changes gradually as one moves Gulfward from inland freshwater swamps dominated by bald cypress, Taxodium distichum, and tupelo gum,
Nyssa aquatica, to brackish and saline marshes dominated by two species of grasses, wiregrass, Spartina patens, and oystergrass, Spartina alterniflora, respectively (personal observation). Spartina alterni- flora comprises about 65% of the total salt marsh (Chabreck, 1970).
Other less frequent species include black rush, Juncus roemerianus; salt grass, Distichlis spicata; batis, Batis maritima; glasswort,
Salicornia virginica; and black mangrove, Avicennia germinans (Chabreck op c i t .)
The tidal cycle is largely diurnal with a small semidiurnal component occurring a t times of minimum ti d a l range. C h a ra c te ris tically, there is one high and one low tide daily except during the semidiurnal period when there are two highs and two lows daily. Semi monthly tropic and equatorial tides occur with an equatorial tidal range of .07 meters and a tropic ' tidal range of slightly more than .67 meters (Day et al., 1972). Highest tides occur from August to
October and lowest from December through February. Meteorological factors often have a greater influence on tidal range than lunar and solar forces. Strong northerly winds and high barometric pressure in the winter lower water levels drastically and lengthen the duration of ebbing tides while reducing the range of flooding tides. South to southeasterly winds and low barometric pressure have the opposite effect. The latter usually occurs in the late spring and early fall and accounts for occasional complete flooding over the top of the marsh grasses at this time. Due to the shallow depths through most of the area and the soft, mucky bottom, turbidity is characteristically high.
Salinity decreases gradually through the basin system reaching 1 to 2 ppt. in the vicinity of Lake Salvador (personal observation). Salinity is determined largely by the stage of the Mississippi River, local run off from rainfall and wind direction and its influence on tidal flow
(Day et a l., 1972). Water temperatures usually are about the same as the current air temperature and do not vary more than a degree between top and bottom due to the shallow water and vertical mixing brought about by winds, waves, and currents. The nature of the bottom sediments changes from almost pure sand and silty sand in Caminada Pass to sandy silt and clayey silt further north up the bay system (Barrett, 1971).
Oyster and clam shell fragments are found concentrated in the bottom sediments where salinities are between 5 and 15 ppt. Organic detritus
(dead plant and animal tissue in various stages of degradation) makes up a large proportion of the bottom sediments, particularly in the spring when high tides wash out the large dead standing crop from the streamside vegetation which has accumulated through the low tides during the winter.
Description of Sampling Stations
Seven sampling stations were selected in the brackish and saline
<1 marshes of the Caminada Bay system. The stations are located between
Caminada Pass, which is the major tidal pass draining Caminada Bay and
Little Lake, about 24 kilometers to the northwest. Each station was 15
selected to represent a particular type of habitat. Proceeding from the
Gulf northward, sampling stations were of the following habitat type:
shallow sand beach and surf zone, deep pass, small shallow saline marsh land, large open bay, tidal channel between two bays, brackish
marsh bay, and a dead end oil canal. Samples both near the shore and
farther offshore were taken at all stations. A specific description
of each sampling station follows. All depths given are the average
depths at which collections were made. Depths did not vary more than
.6 meter at any one station throughout the study. Salinities for each
station are given In the results section. A map of all stations Is
presented In Figure 1.
Station 0 Is located on a point bar on the eastern Gulf side of
Caminada Pass as it enters the Gulf. It averaged 1 to 1.5 meters in
depth along the shoreline with a silty-sand bottom. A noticeable
trough-bar sequence is developed parallel to the shoreline consisting
of alternating troughs of about 2 meters of water between shallow bars
of .3 to .6 meter depth. In October of 1971, construction of a stone
jetty was initiated on the eastern edge of Caminada Pass and the entire
station was filled in with sand pumped by a dredge from the Pass. From
October 1971 to June 1972, a similar beach habitat approximately 100 meters to the east along the shoreline was substituted as Station 0.
Station 1 is located in the northern end of the main section of
Caminada Pass which connects Caminada Bay to the Gulf of Mexico. It
is 6-10.5 meters deep on the western side and has a silty sand bottom.
This station is probably the main channel of migration for fishes
moving both in and out of Caminada Bay. Tidal flow is often very Figure 1. Map of Caminada Bay system and sampling stations. 16
2 9 °3 0 ‘
STUDY LITTLE AREA LOCATION MAP LAKE
GULF
OF MEXICO jjy;« * v v .V ,y ..'; ------O i > ,' ', \v . ' • ,% Wi* J 1 ,' J.v ' • *'J» t ! .A -A li*\ O- i ^ \V v ? ^ V ,^ S k '|
BA RAT ARIA
w. 't/Champagne 2 9 °2 0 ’
wmmm
m m CAMINADA BAY m m
GULF
MEXICO
29°10‘ Naut. miles L 90° 10' 90° 17
strong through this pass; Barrett (1971) reports a flood flow of 627 million cu. feet and an ebb flow of 653 million cu. feet through
Caminada Pass. The northern shoreline of this station is part of an
island which is nearly completely covered by small black mangrove,
Avicennia germinans.
Station 2 is in the eastern lobe of Airplane Lake, a small shallow marsh lake which is shaped like an hour glass. It has an average depth
of 1 meter and a sandy silt bottom containing large amounts of decom posing organic detritus. Oystergrass, Spartina alterniflora, comprises
about 80% of the emergent macrophytic vegetation. Saltgrass, Distichlis
spicata, and black rush, Juncus roemerianus, are found on the streamside
levee and in isolated pockets in the interior marsh.
Station 3 is in Bay Lizette, a northwest corner of Caminada Bay where the southwest Louisiana canal enters the bay. The station parallels a line of buoys which marks a channel dug through the bay.
The depth averages 2 to 3 meters in the channel and 1 to 1.1 meters on
the adjacent flats. The bottom is composed mainly of sandy silt.
Shoreline vegetation is mostly Spartina alterniflora.
Station 4 is a channel between Fishermans Bay and Oaks Bay. It
is 3 to 3.6 meters deep with a sandy silt bottom containing a large
fraction of oyster and clam shell. Shoreline vegetation is mostly
Spartina alterniflora. Along the streamside levee and spoil banks of
nearby oil canals are two shrubs, buck brush, Baccharis halimifolia,
and marsh elder, Iva frutescens.
Station 5 is located in an intermediate size bay 1.5 to 3 km
east of Round Lake. The station runs parallel to an oyster bed along the western shoreline of the bay. It has depth of 1.5 meters and a sandy silt bottom. Predominant vegetation is stillSpartina alterni- flora with scattered patches of Spartina patens.
Station 6 is located in a dead end oil canal .2km west of King's
Ridge and about 4.8 km south of Little Lake. It is 2 meters in depth, about 30 to 36 meters wide, with a clayey silt bottom. Ruppia maritima, a common brackish water submergent plant, is common on the bottom.
Shoreline vegetation consists of Spartina patens and Baccaris halimi- f o lia . I I I . MATERIALS AND METHODS
Use and Measurements of Sampling Gear
A 16 foot otter trawl, 75 foot bag seine and a 300 foot trammel net were utilized in this study. The 16 foot (4.9 m) nylon otter trawl had mesh measurements of 1.6 cm square and 3.2 cm stretched in the wings and .3 cm square and .6 cm stretched in the cod end. Average measure ments of the trawl width opening were made while towing the trawl and was determined to be 2.5 m. This width opening was determined by tying pieces of string of increasing length between the wings of the trawl and measuring the length of those that broke and those that did not.
The first length that did not break was thought to be the true width opening. Another procedure involved standing in shallow water and measuring the distance between the trawl wings immediately after the trawl had been pulled. Measurements for both methods averaged 2.5 m.
Station tows were made for 5 minutes at 2200 rpm at a speed of approximately 3 knots. Dragging time was regulated by a stopwatch and rpm by a tachometer mounted in the boat. Trawling was always done in
the same direction in as straight a line as possible. Timing began when the otter boards spread the net to its full width caused by the
forward motion of the boat. The starting and ending point at each
station was a stationary landmark on shore or in the water such as a marshy point, wood stake or buoy. Based on repeated measurements
during different hydrographic conditions, the bottom sampled by this
trawl in 5 minutes at 2200 rpm was 333 linear meters (333 m). Swept
19 20 area per station was calculated by multiplying the bottom sampled by o the trawl opening (2.5 m) and was calculated to be 832.5 m . This swept area figure was divided into the total fish weight (or individual species weight) taken in each drag to obtain biomass estimates avail- 2 able to the trawl in g/m .
The 75 foot (22.7 m)nylon bag seine had mesh measuring .6 cm knot to knot and 1.2 cm stretched throughout its entire length. The depth of the net from lead line to plastic float line was 2 meters and the bag measured 2 m deep by 2 m wide. The area fished by the seine was c alc u la te d to be 760 m^ which was determined by m ultiplying the distance seined (50 m) by the net opening when being fished (15.2 m). The latter figure is based on the seine being 2/3 open when being pulled through the water. Although the seine was 22.7 m long, the a c tu a l working length when fish in g was about 15.2 m. This net opening was maintained as nearly as possible while seining. Seining distance was marked off along the shoreline beforehand by stretching a calibrated meter tape parallel to the seining area and marking the beginning and ending points with some recognizable object.
Seining was done by two methods, both of which covered the same swept area. In 45 of 47 collections, the seine was pulled for 50 meters parallel to the shoreline by two workers, one immediately on the shore line and the other 50 feet out. Walking on the soft mucky bottom and pulling the seine at the same time was not an easy task but it was accomplished as rapidly as possible. Near the end of the haul, the outer worker would swing straight in to the shoreline and the seine dragged out of the water while keeping the lead line on bottom and funneling the fish from the wings into the bag of the seine. The second method was used only tw ice, once in November and February. I t was employed when the water was too cold or deep to wade through. The net was set from the boat and hauled in toward shore with 50 meter spreader lines. These lines were bridled to the brail poles and pulled in so as to keep the seine 2/3 open. One worker was set out on the shoreline with one spreader line. The boat was then backed out perpendicular to shore until the 50 m line came taut, then the seine was paid out parallel to shore and the brail poles stuck slightly into the mud to maintain the seine in an upright position. Upon reaching shore with the remaining 50 m line, the seine was hauled in.
The 300 foot (90.9 m) nylon trammel net used at Stations 2, 4, and
6 had small mesh 2.5 cm square and 5.0 cm stretched and large mesh 24 cm square and 47.5 cm stretched. The trammel net was-2m deep from lead line to plastic float line. It was composed of a wall of small mesh between two walls of larger mesh. The principle upon which the trammel net works involves the formation of an overlapping pocket between the large and small mesh when a fish strikes the net. Fish of the appropri ate size are also gilled between the webbing of the small mesh. The trammel net was fished by setting it in a semi-circle out from shore.
Initially it is piled up on a large flat board on the bow of the boat for easy removal in making the set. One worker is placed at the sampling station on shore with one end of the net. Another pays out the net from the bow of the boat as a third person poles or backs the boat out from shore. The net is strung out to its full length and brought into shore forming a semicircle. Both ends are then brought together by walking 22 along the shore and the fish removed as the net Is pulled ashore. Sam- 2 pling area of the trammel net was calculated to be 1327.4 m . This figure was arrived at by determining the area of a half circle and converting this into square meters.
A 16.5 foot Boston Whaler boat with an 80 h.p. Mercury outboard motor was used for sampling during the entire tenure of the study. This boat proved to be a very stable working platform and a good reliable boat in the shallow marshes. It was also capable of handling rough weather safely. Base camp for this study was a leased Sea Grant camp which LSU had acquired at Cheniere Caminada about one mile west of
Caminada Pass. Boats, equipment, nets, and other required gearwere kept here.
Station Sampling Frequency
Seven sampling stations were chosen for study as described in the previous section. It was impractical to sample all stations at every sampling period with all three types of gear due to the amount of time required, the distance between sampling stations and the lack of per sonnel. Consequently, a sampling schedule was established and followed through the entire period of study. Samples were taken every three weeks from March 1971 through June 1972. A three week intervalwas thought to be adequate for getting reliable and accurate samples. All stations except the beach station were utilized as trawl stations and were sampled each collecting trip. Station 0 (the beach station) was sampled only with the bag seine. Stations 1, 2, 3 and 5 were sampled with the seine and 2, 4 and 6 with the trammel net. Seine and trammel net collections were made at the selected stations every third trip at 23
9 week intervals with sampling set up in staggered fashion so each collecting trip would involve making 10 collections. This sampling sequence is presented in Table 1. Station 2 (Airplane Lake) was sampled with all three types of gear because it was the center of many other intensive Sea Grant studies and we wanted to obtain as much bio logical data as possible from this one location.
Hydrographic Parameters
On each collecting trip, observations and records were made of water depth, time of sample, tide range and stage, wind direction and velocity, cloud type and cover, air and water temperature, and salinity.
Depth was determined with a Raytheon depth indicator. Predicted tidal range and times of high and low tide were obtained from tide tables published by the Coast and Geodetic Survey. Wind direction and velo city and cloud type and cover were estimated by visual observation.
Air and surface water temperatures were recorded at each station with a mercury Celsius thermometer. Salinity determination for each station was' made with an American Optical T/C refractometer. All hydrographic data and field notes were recorded on dittoed data forms.
Processing of Samples and Laboratory Procedure
Immediately after capture, fish were placed in labeled plastic bags on ice. This reduced weight loss to a minimum before weighing.
It was felt that fresh weight would be more reliable than preserved weight. Therefore, counts and measurements were made before placing specimens in formalin. Representative samples were preserved in 10% formalin for one week. After soaking in water for a short period, Table 1
Sampling Schedule
Trip 1 2 3 4 5 6 7 8 9 10 11 CM 00 Station Date 3/26/71 4/16/71 5/1+7/71 5/25/71 6/15/71 7/7/71 r- 8/28/71 9/21/71 10/14/71 11/4/71
0 S S SS s S SS S 1 T T TS T T TS T T TS TT 2 T TTR T T TTRS T T TTRS T T TTRS 3 TT T TS T T TS T T TS T 4 T T T TTR T T TTR T T TTR T 5 T T TS T T TS T T TS TT 6 TTT T TTR T T TTR T T TTR
Trip 12 13 14 15 16 17 18 19 20 21 22 Date 11/23/71 12/16/71 1/12/72 2/2/72 2/24/72 3/14/72 4/4/72 4/29/72 5/17/72 6/7/72 6/28/72
0 SSSSS S SSS S S 1 TS T T TS T T TS T T TS T 2 T T TTRS T T TTRS T T TTRS T T 3 T TS T T TS T T TS T T TS 4 T TTR T T TTR T T TTR T T TTR 5 TS T T TS T T TS T T TS T 6 T T TTR T T TTR T T TTR T T
T - 16' Trawl Trawl Stations - all except 0 TR - 300' Trammel Net Seine S tatio n s - 0, 1, 2, 3, 5 S - 75' Bag Seine Trammel Net S tatio n s - 2, 4, 6
fO -p- 25 specimens were then placed in 40% isopropyl alcohol and deposited in the
Louisiana State University Department of Marine Sciences fish collection.
All samples were processed in the lab soon after field collection.
This was usually done on the same day of collection. However, on a few collecting trips, very large samples could not be processed on the same day but were done the following day after refrigeration. The following data were recorded on a ditto form for samples from each station: number of species, individuals per species, total and individual species biomass
(grams), species mean length and range (total length in mm), and order of relative abundance. Total length was measured to the nearest mm on a calibrated meter fish measuring board and weight determined to the nearest 0.1 gram on an Ohaus dial-o-gram 1600 g capacity balance. Addi tional data recorded on the same form included the date of collection, station number, collection number, total number of fish and gear used.
A second form was used for Atlantic croaker length-frequency data.
Croakers were chosen for detailed analysis so that an accurate estimate of production for one species could be made. Croakers were measured and placed in 5 mm length groups. Total number in each length group, total number of croakers, total and mean weight, length range and modal length were also recorded. Individual weight of 25 croakers was determined from each collection for calculation of a length-weight relationship.
Keys used in the identification of fishes were Breder (1948),
Eddy (1957), Gowanloch (1933), Dawson (1969), Anderson (1966, 1967),
Gutherz (1967), Parker (1971), Boschung (1956) and Jordan and Evermann
(1896). Nomenclature and taxonomy used were patterned after Bailey et a l .
(1970). 26
Analysis of Field Data
Length-Frequency Distributions - Use of length-frequency distribu tions is a standard way of assessing age and growth in fish populations.
Length-frequency analysis is based on the expectancy that frequency analysis of the individuals of a species of any one age group collected on the same date will show variation around the mean length according to normal distribution (Lagler, 1956). There will be a clumping of age groups about successive given lengths and size ranges which enables the population to be divided by year classes. Numbers of individual fish taken in each 5 mm length group during each collecting trip were plotted.
By following the change in mean, modal, or extreme length of fish collected during each trip, an estimate of growth was obtained. Gear selectivity for different length groups of different species may reflect a biased estimate of true abundance. To counteract this, length- frequencies were calculated for all three gear types combined.
Length-weight Relationship - It is often beneficial to know the weight of a fish at a certain length and vice versa when only one meas urement has been taken. This relation is based on the cube law that growth represents an increase in three dimensions whereas length measure ments are taken in one dimension. The relationship is log w = log a + n log 1
where w = weight in grams
1 = length in millimeters
a + n = constants.
Procedure Used in Calculating Fish Production
Two methods were utilized in calculating an estimate of fish 27 production. The first is based on the direct measurement of secondary productivity and the second is an indirect estimation by calculation from primary productivity data. Apparently the first method has been us^d only once before in an estuarine habitat (Hellier, 1962) and the second is after the method of Ryther (1969) and Wiley (1972).
Direct estimation was made by using the Allen graphical method
(Allen, 1951) and the Ricker numerical method (Ricker, 1946). In
Allen's graphical method, the number of individual fish (N) in the population at successive time intervals is plotted against the mean weight (w) of an individual in the same interval of time. The pro duction in a small interval of time would be equal to NAw where Aw is the growth in mean weight of the population in the time interval.
Summation of the production in each time interval will give the total production during the time considered. Mean weight was determined in the following way. Length-frequency distributions were plotted for all croakers taken at all stations with combined gear (Table 17). While recruitment was occurring from November to April, the change in length for the largest fish taken each sampling period was taken as the growth rate for that period. Recruitment of 11-25 mm fish represses the modal and mean lengths during this period but has no effect on the apparent growth rate of the largest fish. From May to October, the change in mean length was used to calculate growth rate rather than the change
in length of the largest fish. Recruitment has stopped and emigration out of the study area has begun which draws off the larger fish lowering
the apparent growth rate. Thus change in mean length is a more accurate measure of growth from May to October. It must be assumed that the growth rate for all length classes is the same as for the mean and largest length. The length increase was added to the mean length for. each sampling period. This represents the length that the average fish would be at the end of that sampling period. This length was converted to mean weight by using the length weight relationship determined for fish in my sampling area. Subtracting w-^ from W2 gives the increase in mean weight which has occurred through growth during each time inter val. Multiplying this change in mean weight by the number of fish taken each month gives the production for that time interval. Ricker (1946) formulated production during At as:
P = GB
where G, the instantaneous growth rate, equals
log e W£ - log e w^ At
and B, the mean biomass, is _ Bi + Bo B = - l —
Instantaneous growth rates and mean biomass were calculated for each time in te rv a l from November to October and summed to get to ta l pro duction for the year. Dividing the number of grams produced by the o sampling area gives the production estimate in terms of grams/meter / year. Both calculations of production were then compared for relia bility and averaged to get the best estimate.
Ryther (1969) obtained indirect estimates of total annual fish production of the world's oceans by extrapolating from the known pri mary production of the various types of marine environment. Based on 29
the number of trophic levels and the ecological efficiency factor used, estimates ranging from 50 to 300 g carbon/ra^/year were calculated. It must be assumed when using this method that between 10 to 20% of the
organic matter of the primary producers is transferred to both the herbivorous and carnivorous fishes. Wiley (1972) applied this method
to the Patuxent River area in Maryland and calculated potential pro
duction for herbivores, 1st and 2nd stage carnivores at 10, 15, and 20%
transfer efficiency factors. I used the same method and calculated
indirect estimates from the primary productivity data of Kirby (1971). IV. RESULTS AND DISCUSSION
Major Physicochemical Conditions
Important physical and chemical parameters affecting fish biomass
and abundance were measured and recorded. Physical data is summarized
in Table 2. In Table 2, tide*range refers to that predicted by tide
tables and cloud cover is based on a rating scale with 0 being clear and 1.0 completely overcast. Although an interacting complex of factors were involved, temperature and salinity were among the dominant factors
affecting the fish population. Other factors which may affect seasonal rhythms of estuarine fishes are photoperiod, evolutionary history, mean
sea level, changes in osmoregulatory capacity, spawning success, and
interspecific competition. None of these factors were investigated but
should be a topic of future research.
Temperature - Mean trip surface water temperatures for the Caminada
Bay System are given in Figure 2 and Table 3. The mean w ater tempera ture for the period of March 1971 to June 1972 was 23.7°C. The maximum temperature recorded was 35°C at station 2 in June and the minimum 12°C at station 3 in February (Table 3). Temperatures started to increase
in February and continued to rise until July. Temperatures rose above
20°C by April with the greatest increase in March, April and May.
Temperatures began to decrease in September, falling most rapidly in
October and November.
Surface water temperatures usually were two or three degrees higher at the upper bay stations than at the lower bay stations. Occasionally in the winter this was reversed with the southern bay water temperatures
30 Table 2
Summary of Physical Data - Caminada Bay Area
Tide Tide Wind Wind Cloud Cloud A ir Date Stage Range D irection V elocity Type Cover Temp °C Comments mph
3/26/71 High .3 1 E 13-15 Cum .1 11 4/16 R ising 1.3' E 5 Clear 0 26 5/7 High — SE 5 Cum .9 28 5/25 Falling 2.0' SE 5 Cum .5 31 6/14 R ising W 12-15 Cum .1 32 7/7 High Slack 2 .0 ' - Calm Clear 0 30 7/28 High .4 ' S 3-5 Cum .3 29 8/28 F a llin g — NE 5-7 Cum .5 27 9/21 F a llin g 1.0* NE 10-12 Cum .3 29 4 days after Hurricane E dith 10/14 Falling .5 ' NE 5 C irrus .2 25.5 11/4 F a llin g 2.5' NE 20-30 Clear 0 17 1st cool front 11/23 Very High 1 .5 ' SE 25-30 Cum 1.0 16 Raining 12/16 Low — S 3 Cum .2 23 1/12/72 R ising E 2-3 Cirrocum .4 18 2/2 F a llin g -- SE 8-10 Cum .9 17 Cool front 2/24 Rising 2 .0 ' S-SW 5-8 Cirrocum .3 20 Extremely low tid e s 3/14 R ising — - Calm Cirrocum .2 20.5 4/4 Rising 1.5' S 2-3 Nimbo- N 20-25 cumulus 1.0 30 Rain cool front 4/29 High 1.6' S 15-20 Cum .8 24 Tides extremely high 5/17 Rising -- N 5-8 Cum 1.0 25 6/7 High 1 .0 ’ NE 3-5 Clear 0 28 6/28 R ising 1.0' W-SW 5-10 Cum .1 30 Figure 2. Mean surface water temperatures in the Caminada Bay system from March 1971 - June 1972. I I I I I I I I I I I I 3/26 4/16 5/7 5/25 6/14 7/7 7/28 8/28 9/21 10/14 11/4 I 1/23 12/161/12 2/2 2/24 3/14 4/4 4/29 5/17 6/6 6/28
1971 1972- Table 3
Water Temperatures °C in the Caminada Bay Area March 1971 - June 1972
S ta tio n 0 1 2 3 4 5 6 Trip Date Air T. Caminada A irplane Bay Fisherman's Oyster O il Beach Pass Lake L izette Bay Bay Canal
1 3/26/71 11 18 19 18 18 18.8 18.8 2 4/10-17 21 22 23 23.5 23 — -- 3 5/1+7 28 24 25 26 26 25.5 21 26.5 4 5/25-26 30 28 27.8 28 29 27.5 28 29 5 6/14-16 31 31 28 35 31.3 31 31 33 6 7/7-8 30 30 31 29 29.5 29.5 30 31.5 7 7/28-29 29 28 28 27 28 28 30 31 8 8/28-29 27 28 29.5 28 29 29 29 30 9 9/21-22 29 28 28 28 28 28 29 29 10 10/14-16 25 23 23 24 25 24 25 26 11 11/4-5 16 16 18 17 16 17 17.5 18 12 11/23 16 15 16 15 15 15 15 15 13 12/16 23 22 22.5 24 23 24 24 25 14 1/11-13/7218 17 17 18 20 19 21 21 15 2/2 17 15 14 14 12 12.5 12.5 13.5 16 2/24 20 19 18 22 19 20 20 21 17 3/14-15 20.5 21 21 23 21.5 22 22 22.5 18 4/4/72 30 21 21 22.5 22 21.5 21 21.5 19 4/29-30 24 22.5 22 21 21.5 22 23 24 20 5/17-18 23 24 24 25 26 25 25 26.5 21 6/7-8 28 26.5 27 28.5 28.5 28 29 29.5 22 6/28-29 30 26 26.5 28 29 28 29 30
Mean 24 23.2 23.1 23.9 23.7 23.5 23.8 24.9 34 wanner than the north bay. Little variation existed between the surface
and bottom water temperatures due to the shallow nature of the bay and
vertical mixing brought about by winds, waves and currents. Generally,
the water and air temperature were the same or at most a degree or two
d if f e r e n t.
The monthly mean and range in water temperatures as taken from the
continuous recorder at the Grand Terre marine laboratory on Barataria
Pass is presented in Figure 3. Data taken from this recorder are plotted
for the time period of ray study from March 1971 to June 1972. Water
temperatures ranged from a low of 8°C in February to a high of 32°C in
June. Louisiana Wild Life and Fisheries Commission Oyster Division data
fo r an eig h t year period in the 1960's shows the minimum mean monthly
temperature of 12.8°C occurring in January and the maximum of 28.7°C in
August. Figure 3 presents a more accurate pattern of temperature
fluctuati Oh because it is based on temperatures recorded daily while
my temperature data (Figure 2)were taken on sampling trips at three week
intervals. The greatest variation in water temperatures was from Novem
ber to February when alternating cold air from the north and warm air
from the Gulf caused temperatures to rise and fall rapidly. Least varia
tion occurred from June to September when the Bermuda high pressure ridge
stabilized conditions.
Salinity - There was a gradual decrease in salinity northward through
the study area. Salinities averaged 24 °/oo on the beach at Caminada
Pass and 8 °/oo at station 6 which is approximately 24 km to the north west. Further north through the Barataria Basin system, salinities
approach 1 to 2 °/oo near Lake Salvador and essentially fresh water in Figure 3. Monthly mean and range of water temperatures taken from continuous recorder at Grand Terre Marine Laboratory, March 1971 - June 1972. Temperature °C O O M 0-0 00 M ^ 00
Date 36 the cypress swamp around Lake Des Allemands (personal observation).
Salinities were highest in June 1971 throughout the study area when they averaged 26.9 °/oo and lowest in February 1972 with an average of
8.5 °/oo. The highest salinity measured during the sampling period was
34 °/oo in Caminada Pass on June 14, 1971, and the lowest 0.2 °/oo at station 6 on February 2, 1972. Generally, salinities were highest in the spring and summer and lowest in the fall and winter. Salinity data are presented for each station in Figure 4 and Table 4.
Mississippi River discharge, runoff from rainfall, tidal range, and local winds are the major factors inducing variations in salinity.
Barrett (1971) reports that during high river discharge (March through
May), river waters entering the Gulf from Southwest Pass are the main cause of salinity dilutions from the mouth of this pass westward along the coastline to the vicinity of Timbalier Bay. On occasion, Mississippi
River waters extend northward into Barataria Bay in excess of ten miles and may be responsible at such times for salinities in the upper bay being higher than those in the lower bay (Barrett _op. c it.). Variations in rainfall affect salinities in the upper bay more than the southern bay but may decrease salinities in the southern bay when accompanied by northerly winds and falling tides. The predominant winds are from the east and southeast particularly in the spring and summer. These winds combine with high river discharge to push fresh waters and nutrients into the bay. Fresh water discharge from the river is one of the main factors maintaining high productivity in this system (Day et a l., 1972).
High tropic tides in April and September flood the marshes and bring in waters of high salinity from the Gulf. This was not the case on the
September 1971 sampling trip because Hurricane Edith four days previously Figure 4. Salinities (°/oo) at each station from March 1971 - June 1972. Salinity %o 10 5 30 /6/6 / 52 61 77 /8 /8 /11/4 14I12 2/1 /2 / 22 31 44 /9 /7 / 6/28 6/7 5/17 4/29 4/4 3/14 2/24 2/2 16 1/12 / 12 I1/23 11/4 10/14 9/21 8/28 7/28 7/7 6/14 5/25 5/7 3/264/16 . a Lzte v. 19 Ave. Lizette Bay 3. — 0 . aiaa as ec Ae 24 Ave. Beach Pass Caminada 0. . ipae ae v. 21 Ave. Lake Airplane 2. . aiaa as hne Ae 23 Ave. Channel Pass Caminada I. . ihra’ Bay Fisherman’s 4. . igs Ridge King’s 6. i Cnl v. 8 Ave. Canal Oil . ytr Bay Oyster 5. v. II Ave. v. 14 Ave. Vj3 Table 4
Salinities °/oo in the Caminada Bay Area March 1971 - June 1972
s ta tio n Trip Date 0 1 2 3 4 5 6 Caminada A irplane Bay Fisherman's Oystei 011 Beach Pass Lake L izette Bay Bay Canal
1 3/26/71 __ 19 25 22 18 12 15.5 2 4/16-17 -- 28 22 23 16 10 8 3 5/1+7 25 26 26 26 22 20 16 4 5/25-26 25 20 27 26 25 21 16 5 6/14-16 32 34 26 26 26 24 20 6 7/7-8 31 26 24 24 20 15 8 7 7/28-29 30 29 21 18 16 12 8 8 8/28-29 25 24 22 22 16 10 4 9 9/21-22 15 12 16 12 7 4 1 10 10/14-16 18 16 18 13 9 6 2 11 11/4-5 24 19 22 18 12 8 6 12 11/23 28 25 26 20 18 13 6 13 12/16 24 24 22 19 15 12 6 14 1/12-13/72 17 14 15 14 10 8 4 15 2/2 15 13 13.5 8 6 3.5 0.2 16 2/24 26 26 12 10 4 2 1.5 17 3/14-15 23 22 18 14 8 5 3 18 4/4/72 28 28 20 18 10 6 4 19 4/29-30 22 22 22 20 18 16 12 20 5/17-18 20 18.5 20 15.5 9 6 7 21 6/7-8 23 19 22 18.5 14 10.5 8 22 6/28-29 34 34 23 28 18 14 12
Mean 24 23 21 19 14 11 8 39 had dumped torrential rains on the area drastically decreasing salinities.
Caminada Bay Fish Population
During the course of this study, a total of 97,223 fishes of 100 species belonging to 82 genera and 46 families were collected quantita tively with 16 foot otter trawl, 75 foot bag seine, 300 foot trammel net and Antimycin (Table 8). Additional qualitative collections were occasionally made with dip net, hook and line, 10 foot seine, 32 foot trawl and hand capture in order to sample additional habitats and deter mine more accurately the species composition in the study area. A total of 63,863 fish were taken with the trawl, 31,092 with the seine, 531 with the trammel.net (Table 13) and 1,754 with Antimycin. A total of 199 sam ples were made with all three types of gear (132 with trawl, 47 with seine, and 20 with trammel net). These fishes weighed 376.1 kilograms w ith a mean biomass of 16.44 g/m^ (Table 8). The m ajority were seasonal migrants utilizing the estuarine system as a spawning, feeding or nursery a re a.
Biomass was highest in August and lowest in February (Figure 8) for data representing combined gear. Secondary peaks in biomass occurred in
April and October. Biomass of fish taken with each gear and at each
station showed the same general pattern (Figures 5-7 and 12-25 in Appen
dix) .
The more saline portions of the study area supported a higher biomass
and a greater number of species than the upper brackish marshes (Table 6).
The brackish marshes were sanctuaries for some juvenile estuarine depen
dent species which were more abundant in low salinity. Species diversity was greatest throughout the study area from July to October when water temperatures were near maximum (Figure 9). Species d iv e rs ity was lowest from November to February.
Numerical abundance was highest in March with a secondary peak in
August followed by a sharp drop in September and a minimum in November
(Figure 8). Numerical abundance generally increased towards the lower salinity areas although it was highest at station 2 where 32% (30,891) of all fishes were taken (Table 6).
The bay anchovy, Anchoa m i t c h i l l i , was more abundant than a l l other fishes combined, constituting 54,1% of the total number and 9.1% of the total biomass. Twenty-seven species comprised 97% of the total number and 79.2% of the total biomass. There were 22 species for which only one specimen was collected. Estuarine fish populations seem to consist primarily of large numbers of a relatively few species which are resi dent or estuarine dependent and smaller numbers of a larger group of species which are primarily marine. Juveniles of this latter group are often taken in inshore waters. Of the 113 species known to be present in the study area, 3 can be classified as freshwater fishes, 3 as semi- anadromous, 32 species as estuarine, 40 species as estuarine dependent, and 35 species as primarily marine (Table 10).
The fact that estuaries are important nursery grounds for fishes of the commercial and sport fishery is well known and well documented.
However, it is very important and bears stressing. Dunham (1972) reported 65 species of fishes taken in industrial bottomfish catches off Louisiana, 66% of which inhabit Caminada Bay during juvenile stages.
Every species except the silver seatrout, Cynoscion nothus, which makes up a significant portion of the total weight and number of the industrial catch is estuarine dependent. The Atlantic croaker alone comprises 62.3% of the total number and 65.5% of the total weight of industrial bottom- fish e s landed in Louisiana (Dunham, .1972). The A tla n tic croaker is a member of the Sciaenidae, a family composed primarily of estuarine depen dent fishes which are among the most important commercial and sport fishes taken in Louisiana. In terms of volume, Gulf menhaden and Atlantic croaker are the two most important industrial and commercial fishes taken on the Louisiana coast (Lindall et al., 1971). Most of the major sport fishes caught in the coastal waters of Louisiana are estuarine dependent.
These include spotted seatrout, red drum, black drum, southern flounder,
Atlantic croaker, sheepshead, Spanish mackerel, bluefish, jack crevalle, cobia, tripletail and southern kingfish.
Seasonal Biomass and Abundance
Trawl Biomass - The 16 foot otter trawl used in this study is selective for slow swimming small benthic organisms. Any study relying strictly on trawl data will under represent the larger fast swimming fishes and reflect an unduly large proportion of juvenile fishes.
Efficiency of the trawl as a means of capture varies widely for differ ent species of fish and different length classes of each species. Other factors affecting trawl efficiency include the water temperature, depth, bottom type, towing speed and mesh size.
Figure 5 shows biomass of fishes caught with the trawl at all stations combined was highest in April 1972 (2.97 g/m^ wet weight) with a sm aller peak in August 1971 (1.86 g/m ^). The annual mean traw l biomass Figure 5. Biomass of trawl caught fishes in the Caminada system March 1971 - June 1972. Biomass grams wet wt. per meter .0 3 2.0 /6 /6 / 52 61 77 /4 /8 /1 01114 /321 11 23 /4 /4 / 42 51 67 6/28 6/7 5/17 4/29 4/4 3/14 2/24 2/3 1/12 I1/2312/16 1/4 10/141 9/21 8/28 7/24 7/7 6/14 5/25 5/7 4/16 3/26 en10 g/m Mean:1.03 1971 Date 1972 ^3 43 o throughout the sampling period was 1.03 g/m . Trawl biomass was lowest 2 from November 1971 to February 1972 (.3 7 -.4 0 g/m ) . S im ilar p a tte rn s were found by Forman (unpublished, 1971) in Lake Grande Ecaille on the eastern side of Barataria Bay. His data are an average of three stations 2 in Lake Grande Ecaille. He reported an April peak in biomass of 2.7 g/m 2 wet weight and minimum biomass in January (.25 g/m ) . My data also in d i cates an April peak in 1972 which is probably attributable to the in shore m igration of p o s tla rv a l fish e s from November to A p ril. In 1971, sampling started in late March. Biomass was decreasing then and an April peak was not evident. The spring peak possibly occurred earlier in March
1971 before sampling began. Dunham (1972) found that fish larvae being carried in through Caminada Pass on rising tides were most abundant in
March in 1971 and April in 1972. This corresponds with my data and suggests that I missed the March peak in 1971. Spawning of a large number of estuarine dependent species occurs offshore in the fall and early winter and larvae are carried by currents to the vicinity of the tidal passes connecting the bay system to the Gulf. These fish enter the bays as postlarvae and most move to the upper estuary. While the
April peak is composed of small juvenile fishes of a few species, the
August peak is composed primarily of larger sub-adult fishes of a wider variety of species.
Natural mortality is very high among larval and postlarval fishes
(Greze, 1967) contributing to the rapid drop in numbers and biomass after
April. In addition to high mortality rates, offshore emigration by cer ta in members of the Sciaenidae (Micropogon undulatus and Leiostomus xanthurus) and Clupeidae (Brevoortia patronus) begins in May (Table 7). This movement also co n trib u tes to the decrease In biomass through the e arly summer. The commercial shrimp fish in g season In Caminada Bay Is probably most Intense from May to July (personal observation) and may also be a factor In decreasing biomass in early summer. An earlier study in th is area (Thomas e t a l. , 1971) in d icated commercial shrimping had a temporary influence in decreasing fish biomass. Many estuarine dependent fishes are taken in shrimp trawling, most of which are discarded as
"trash" fish.
Biomass increased through July and August 1971 probably because sea catfish, Arius felis, and gafftopsail catfish, BaRre marinus, are very abundant after spawning in the summer months. In addition, species of the families Carangidae, Scombridae, Ephippidae, Engraulidae, Stroma- teidae, and Tetraodontidae reach their peak of abundance inshore in the la te summer. Marine fish e s w ith l i t t l e e stu arin e dependency o ften move into the lower bay at this time of year, usually on feeding forays following smaller baitfish. This group includes bluefish, Pomatomus saltatrix, large jack crevalles, Caranx hippos, and sharks. This period
is characterized by the highest species diversity due to the mixture of resident, estuarine dependent, and primarily offshore species. Water temperatures are at a seasonal peak in late summer, salinities are high and hydrographic conditions in the bay are most like those offshore.
McHugh (1967) reported that osmoregulation was easier for the marine forms at higher temperatures and salinities, thus facilitating their movement in sh o re.
After this late summer build-up there was a sharp drop in biomass, probably due to declining water temperatures and salinities. This decrease was very noticeable in September 1971, when biomass declined 9 9 almost four fold from 1.86 g/m4 to .53 g/m . A minor peak is evident o on the November 4, 1971, t r i p (1.23 g/m ). The f i r s t strong cold fro n t
of the year had moved through just prior to and during this collecting
trip causing water temperatures to drop rapidly. The higher biomass at
this time may be attributable to the concentration of fish in deeper
channels and a ctiv e movement Gulfward. Gunter (1945) was among the
first to report the importance of temperature in influencing mass migra
tions of fishes from the bays to the Gulf and vice versa. He states
that temperature is the chief factor initiating seasonal migrations and
other seasonal cyclic actions of the fishes on the Gulf coast. Twenty-
two species of fish were collected in one trawl haul at station one in
Caminada Pass on November 4, 1971. This catch was more than twice the next highest number of species collected at station one and reflects a mass migration of fish through the pass into the Gulf. The biomass at
s ta tio n one was higher on November 4, 1971 (3.52 g/m ) than a t any other
time except during the April 4, 1972, trip (5.25 g/m^) when large num
bers of postlarval and young-of-the-year fishes were entering the pass.
Trawl biomass remained low through February 1972 when inshore movement
of young fish began to increase the biomass to its seasonal peak.
Trawl biomass represented the greatest proportion of the combined
total biomass in April 1972 (93%) when juvenile fishes were abundant and
the lowest proportion of the combined total biomass in July 1971 (12.4%) when la rg e r sub-adults were dominant.
As has been mentioned previously, trawls are selective for small
juvenile fishes and are not effective for all sizes and species. There- 46 fore, biomass estimates based only on the trawl are minimal. Estimates of fish biomass from methods which are less selective indicate that actual biomass may be much higher. Kjelson et al. (1972) compared the effec tiveness of a stationary drop-net to a haul seine in the Newport River estuary of North Carolina. On the basis of 25 concurrent trials, the 9 2 drop-net captured more organisms (.47/nr) and a higher biomass (5.42 g/m ) 2 2 than the haul seine (.14/m and .93 g/m , respectively). However, the haul seine consistently captured the greatest number of species. Hellier
(1962) using a drop-net quadrat reported a winter minimum of 2.0 g/m£ wet weight and a summer maximum of 37.8 g/m wet weight for fish biomass in the upper Laguna Madre of Texas. Hoese and Jones (1963) using a 2 similar drop-net in Redfish Bay, Texas, found a January low of 0.46 g/m and a May high of 4.9 g/m . Jones et al. (1963) using a helicopter borne purse net in Corpus Christi Bay, Texas, found biomass levels ranging from 5.07-18.7 g/m wet weight. Moseley and Copeland (1969) utilized a small portable drop-net for quantitative sampling in Guadalupe o Bay, Texas. They found low biomass in December of about 3 g/m and the highest biomass of 231 g/m^ in June. Hall and Woodwell (1971) using a similar drop-net in Flax Pond, Long Island, New York, found biomass at 2 or near zero from la te November to March but from 50 to 200 g/m during the summer months.
Trammel Net Biomass - The trammel net is effective for large active predatory fishes and larger individuals of species usually not vulnerable to trawl capture. It is not effective for fishes whose girth is less than 2 inches because they are able to escape through the mesh. In this study, the trammel net was most effective on larger specimens of Gulf 47
menhaden, Brevoortia patronus; sea catfish, Arius fells; spot, Leiostomus
xanthurus; spotted seatrout, Cynoscion nebulosus; and striped mullet,
Mugil cephalus. Specimens from 200 to 450 mm were most susceptible to
trammel net capture. The effectiveness of the trammel net may have
been reduced due to improper hanging of the net. When the net was de
signed, not enough slack was allowed between the large and small mesh
and consequently the net was too rigid and did not allow proper "pocket"
formation. Therefore, the net fished more like a large seine and gill
n e t.
Trammel net biomass was h ig h est in October 1971 (5.93 g/m^) and
lowest in March 1972 (1.49 g/m^) w ith an annual mean of 3.58 g/m^ (see
Figure 6). Maximum biomass in October may be attributable to the rela
tively high number of large fishes present in the bays at this time
following a full summer^ growth but preceding offshore migration induced
by low temperatures. Trammel net biomass decreased through the winter and
e arly spring to minimum lev els in March 1972. The fis h fauna in March was composed mostly of postlarval estuarine dependent fishes moving in
shore and of small resident fishes such as silversides, blennies and
gobies, cyprinodonts, and anchovies. With a rise in water temperature
after March, larger fishes again were able to move into the bays and biomass began to increase reaching 5.77 g/m wet weight by June 1973.
Seine Biomass - The 75 foot bag seine was the least selective of the
three gear types. Generally, about twice the number of species at any
one station were taken with the seine as opposed to the trawl and biomass
available to the seine was from 2 to 3 times greater than biomass avail
able to the trawl at stations sampled with both kinds of gear (Table 6). Figure 6. Biomass of fishes taken with 300-foot trammel net in the Caminada Bay system April 1971 - June 1972. Biomass grams wet wt./per meter' 6 2 3 4 5 0 /6 /5 6/14 5/25 4/16 en 35 g/m 3.58 Mean: /8 /8 01 1/ 12/16 11/4 10/14 8/28 7/28 1971 Date 1/2 2/24 /442 5/17 4/29 3/14 1972 6/28 00 49
The seine was more effective because it fishes the entire water column in depths less than six feet. Both benthic and littoral fishes of a wide size range were susceptible to seine capture. Species that rarely ven ture away from the shallow shorelines were susceptible to capture by the seine but not the trawl.
Seine biomass was highest in August 1971 (17.07 g/m ), lowest in 2 2 December 1971 (0.17 g/m ) w ith an annual mean of 4.51 g/m (Figure 7).
This is approximately 4.5 .times greater than the mean trawl biomass.
Since the seine can be fished effectively only in shallow waters, cat ches will be greater when the water is warm and the fish are on the flats and shallow nearshore areas. Biomass generally increased from May 1971 to a peak in August 1971 a f te r which i t s te a d ily decreased to minimum
levels in December 1971. The sudden decrease of biomass on July 28 is difficult to explain but may have been associated with slightly decreasing tem perature and s a lin ity and also m igratory movement o ffsh o re. During the winter months, biomass remained low except for the sampling trips of
January 12, 1972, and February 2, 1972. Large numbers of cyprinodonts were taken at station 2 on the January trip. Cyprinodonts are resident
in the estuarine system and were apparently driven into the sampling area
from nearby tidal creeks and ponds, possibly by cold water temperatures.
On the February trip, a large aggregation of ripe silver perch,
Bairdiella chrysura, were taken at station 0. This raised the biomass
to 12.33 g/m^ but the biomass at stations 1 and 5 were very low at this
tim e. From February 1972 to June 1972, seine biomass flu c tu a te d some what, particularly from February to April. This was probably due to recruitment of large numbers of small fish in the early spring. From Figure 7. Biomass of fishes taken with 75-foot bag seine in the Caminada Bay system Hay 1971 - June 1972. Biomass grams wet wt per meter / 52 61 77 /8 /8 /1 01 1/ 12 21 11 22 /4 /4 / 42 51 67 6/28 6/7 5/17 4/29 4/4 3/14 2/24 2/2 11/23 1/12 11/4 12/16 10/14 9/21 8/28 7/28 7/7 6/14 5/25 5/7 en 45 g/m 4.51Mean: 51
April to June, progressively fewer fish were taken though they gradually increased in size.
Seine biomass represented the greatest proportion of the total biomass in June 1971 (87.6%) and the lowest proportion in December 1971
(3.8%). Again, this is attributable to larger numbers of fishes in the nearshore zone in the warmer months and movement away from these areas during the winter months.
T otal Biomass Taken w ith Combined Gear - Since each gear type has its own selectivity and efficiency for certain species and size ranges of fish, data for all three types of gear were combined in an attempt to better represent true fish biomass. This is presented along with total numbers of fish taken in Figure 8. The total weight of fish taken with each gear was summed and divided by the combined sampling area to give biomass in terms of g/m^ wet weight. I feel that the pooling of data in this way is the most accurate way of estimating true seasonal biom ass. A Maximum biomass taken with combined gear was 4.37 g/nr in August
1971 and minimum biomass was 0.35 g/m^ in February 1972. P a tte rn s of seasonal biomass variation obtained from each gear at combined stations, individual stations with each gear, or individual species were generally similar. Nearly all data compiled on biomass indicate a spring and late summer peak. The same reasoning that was used in explaining these seasonal pulses for the individual gear types also applies here. Com bined biomass levels increased through the spring of 1971 to the August peak after which a general decrease occurred until February 1972. Bio mass again began to increase in late February 1972 reaching a secondary Figure 8. Total biomass and number of fish taken with combined gear at all stations March 1971 - June 1972. Total number of fish per hectare x 1000 /6 /6 / 52 61 77 /8 /892 01 / I12 21 11 22 /4 /4 / 42 51 67 6/28 6/7 5/17 4/29 4/4 3/14 2/24 2/2 1/12 I12/16 1/23 I 1/4 10/14 9/21 8/28 7/28 7/7 6/14 5/25 5/7 4/16 3/26 10 1971 Number/ha. Date ims kg/ha. Biomass 17561 1972- o OQ O O E E U X £ - - £ . Q - Q V V V o E o T J w E V V o DO u> to "\ 53 peak in late April. Biomass then decreased until June when the increase to the late summer peak began. It is obvious that large fish weigh more than small fish; that the trammel net is selective for large fish and the trawl for smaller fish. As a consequence, when the biomass available to all three types of gear is combined, maximum levels occur in August rather than April (as in the case for trawl biomass).
Factors Influencing Seasonal Biomass and Abundance
Temperature - My data indicate that seasonal variation in biomass is primarily affected by the yearly temperature cycle. Figure 9 represents the variation in total biomass and species diversity in relation to mean water temperature from March 1971 to June 1972. Statistical analysis revealed a significant positive correlation between temperature and combined biomass. A correlation coefficient of .52 was found which is significant at the .05 confidence level. This indicates that temperature
is related to '52% of the variation in seasonal biomass. The relationship between temperature and biomass can be observed by following the seasonal trend in Figure 9. Rising temperatures are accompanied by increasing biomass until late August. A sharp drop in temperature occurring from
September to November corresponded with rapidly decreasing biomass. An increase in temperature in December due to an abnormally mild winter may have contributed to the slight increase in biomass from late November 1971
to early January 1972. Another sharp decrease in temperature in February was followed by a similar drop in biomass. Starting in late February
1972, temperature again began to rise to its late summer peak. Biomass
increased to a late April peak, decreased through the early summer, then Figure 9 Total biomass of fish taken with combined gear in r e la tio n to seasonal mean w ater tem perature and mean species d iv e rs ity March 1971 - June 1972. Mean species diversity I0r - 12 /641 57 /5 /4 / 72 82 /1 01 1/ 12 1/6 /2 / 22 31 44 /9 /7 / 6/28 6/7 5/17 4/29 4/4 3/14 2/23 2/2 1/12 12/16 11/23 11/4 10/14 9/21 8/28 7/28 7/7 6/14 5/25 5/7 4/16 3/26 V / \ 9 1 ------+1971 Date tr temperature ater W _ _ _ pce diversity Species — Boas kg/ha. Biomass — — ------: ------1972 .A* .A* h~
Biomass kilograms per hectare x 10 (or grams per m eter2) ■P- \n 55 began to climb to the larger late summer peak when sampling terminated.
By comparing my biomass data with water temperature data in Figure
3, it is evident that the seasonal peak in biomass which occurred in
August 1971 corresponds with the highest mean monthly water temperature and the lowest biomass taken in February occurred when the mean water temperature was lowest. Such a correspondence agrees with earlier stud ies and emphasizes the seasonality and migratory nature of estuarine fish populations.
Gunter (1957) considers temperature to be the most important single factor governing the occurrence and behavior of life. Gunter (1945) states that temperature is the chief factor affecting and initiating seasonal migrations, distribution, and other seasonal cyclic actions of fishes on the Gulf coast. Other authors, notably Joseph and Yerger
(1956), Kelley (1965), Nelson (1969), Parker (1971) and Zilberberg (1966) have stressed the importance of temperature in influencing seasonal abundance and distribution of fishes.
Other workers have noted that estuarine fish biomass is lowest in the winter and highest in the summer. McFarland (1963) found that the winter biomass along a beach at Mustang Island, Texas, was 2.9 g/m^ 2 while the summer biomass was 11.6 g/m . Hellier (1962) observed the same phenomena in the upper Laguna Madre of Texas where the winter bio- o 2 mass was 2.0 g/mz and the summer biomass 37.8 g/m . Moseley and Cope- 9 land (1969) found a December minimum of about 3 g/m and a June maximum of 231 g/m in Guadalupe Bay, Texas. H all and Woodwell (1971) calcu lated winter biomass at near zero and summer biomass from 50 to 200 o g/m in a tidal salt pond on Long Island, New York, and Hoese and Jones 56 O (1963) found a January minimum of 0.46 g/m and a May maximum of 4.9 g/m in Redfish Bay, Texas.
Although biomass in the bay is synchronized to an integrated com plex of chemical, physical and biological factors, I believe temperature is a dominant factor. Temperature is also of prime importance in influ encing time and success of spawning and migratory movements and as such is a dominant factor in determining seasonal number and distribution of fis h e s.
Salinity and Species Diversity - In general, the more saline por tions of the Caminada Bay area supported a higher standing crop biomass of larger fishes and a greater number of species while the upper more brackish marshes nourished greater numbers of individual juvenile fishes of lower biomass. Carlander (1955) found that an increase in the stand ing crop biomass of a body of water occurred as the number of species of fish increases, but maximum crops of selected species were found in lakes and ponds with not more than one other species present. This observation seems to hold in the Caminada Bay estuarine system. Biomass was higher at the more saline stations where a greater number of species were taken.
Individual species biomass, however, was highest when only one or two other species were present. Herke (1971) concluded distribution of estuarine organisms was affected by an interaction of seemingly minor changes in environmental factors which varied in importance depending on the time of the year. He felt that salinity showed the closest corre lation with emigration of fishes.
Gunter (1945) found more species in salty Gulf waters and pro gressively less in upper fresher regions of estuaries. He also noted 57 that the fauna in brackish waters is predominantly marine and that smaller larval and juvenile fishes were better able to withstand low salinities than adults. Adults of many species are restricted to higher salinities. As juveniles grow in the low salinity areas, they begin a gradual Gulfward movement. These relationships have a definite influence on the biomass present in different salinities.
The majority of resident and estuarine dependent fishes found in the study area are euryhaline and capable of thriving in a wide sal inity range. Salinity, in itself, is more important in limiting the distribution and therefore the biomass of stenohaline marine fishes to the lower bay. The presence of lowered salinities in the upper bay pre vents the movement of these fish es beyond the sa lin e p o rtio n s of the lower bay and is apparently a dominant reason for the greater species diversity and biomass in the lower bay.
Food Availability - One of the remarkable properties of the salt marsh ecosystem is the seasonal synchronization of food organisms with the peak of postlarval and juvenile fish populations. In the Caminada
Bay area, most of the micro and macrobenthic organisms including amphi- pods, nematodes, mysids, and zooplankton reach their seasonal peak of biomass in the spring, predominantly April (Day jet a l., 1972). A secondary peak in biomass occurs in August. Mulkana (1970) showed that nannoplankton biomass was maximum in March in Barataria Bay and pointed out the importance of nannoplankton as food energy for filter feeders such as striped mullet and Gulf menhaden. Organic detritus reaches peak levels in the water column after high spring tides flush out the large dead standing crop of Spartina detritus in April and May (Day, op. 58
c it.). Detritus is a primary food source for most of the benthic or ganisms as well as some fishes. These seasonal pulses coincide with maximum biomass of juvenile fishes which also occurs in April and is
represented by trawl biomass in Figures 10 and 11. Hellier (1962) ob
served the correspondence of the rapid spring influx of young-of-the- year fishes with a spring peak in food availability as expressed by the rate of photosynthesis. He also found a direct correlation between fish biomass and temperature and salinity curves. The secondary peak of fish biomass in August is also at least partially attributable to increased
food availability. The maximum biomass of zooplankton (Cuzon du Rest,
1963) and amphipods (Day et a l., 1972) are 11.5 and 4.3 times the maxi mum biomass of trawl caught fish, respectively. After an offshore over wintering migration by the majority of the estuarine dependent fishes,
the biomass of fish food organisms began to increase. Thus, the
seasonal peak in biomass of fishes, benthic organisms and detritus pro duction are synchronized such that abundant food is available in es
tuaries when juvenile fishes move inshore.
Areal Biomass and Abundance
Individual Station Biomass and Abundance - The biomass at each
station taken with each gear Will now be considered. Maximum and minimum lev els of biom ass, mean biomass, abundance, and predominant
species at each station are mentioned. Graphic representation of bio mass and abundance for each station is in the Appendix in Figures 12-25
and a summary of station biomass and abundance is presented in Tables
5 and 6.
Station 0, Caminada Pass Beach - Seine - Except for the sampling Figure 10. Seasonal biomass of trawl caught fishes in relation to seasonal food biomass'(1971). Biomass grams wet wt. per meter 12 — 5 . 4 3 L J Date J AM S Nematodes Amphipods Fish O Figure 11. Seasonal biomass of trawl caught fishes in relation to seasonal production of organic detritus (1971). Monthly organic detritus production grams wet wt/m* x 100
fO ^ O ' o o o ' to
•n
>
-n OO >
OO
O M z
o o to co
Fish biomass kilograms per hectare x 10 (or grams per meter2 61 trip of February 2, 1972, biomass on the beach was highest in August 1971
(32.06 g/m^), lowest in December (no fish) with an annual mean of 5.92 g/m^ (Figure 12). On February 2, 1972, 590 large rip e s ilv e r perch
(Bairdiella chrysura) were taken in a tight aggregation. These fish may have been preparing to spawn. Abundance was highest on the beach on July 7, 1971, when 4,726 fish were taken and lowest in December 1971 when no fish were taken. Gunter (1958) noted the same trend on a beach in south Texas where fishes were most abundant in the spring and summer and scarce in the winter. McFarland (1963) also found biomass in the surf at Mustang Island, Texas, highest in the summer (11.6 g/m^) and lowest in the winter (2.9 g/m^). Station 0 showed the greatest range in biomass of all stations which is probably a reflection of the pronounced seasonality of fish populations on shallow beaches. This station may also have been an ecotone or transition zone between bay and Gulf fishes.
The dominant fishes on the beach were Membras martinica, Anchoa m itchilli, and A. hepsetus, Mugil cephalus, Trachinotus carolinus, Bairdiella " " r ‘ chrysura, and Arius felis. Other species found primarily offshore occurred here and at no other stations in the bay (Table 12).
Station 1, Caminada Pass - Trawl - Caminada Pass is the main tidal pass connecting Caminada Bay and the Gulf of Mexico. Biomass was highest here when fish were migrating either into the bay in April or Gulfward in November. At other times biomass was usually very low. Tidal currents flow rapidly through this area and it apparently is not an ideal habitat for fishes to take up permanent residency. The highest biomass taken was-on April 4, 1972 (5.25 g/m^) (Figure 13). A secondary peak occurred on November 4, 1971 (3.52 g/m ^). The l a t t e r co n sisted of 22 species of 62
fish apparently migrating out to the Gulf for overwintering and spawn
ing. A strong cold front had moved through on this date possibly
trig g e rin g th is mass movement o ffsh o re. Abundance was h ig h e st in
August 1971 when 552 fish were taken, the majority of which were
Chloroscombrus chrysurus and Anchoa hepsetus. Biomass and abundance were lowest at this station in June and July 1971 when no fish were O taken in the trawl samples. The annual mean biomass was 0.91 g/m .
Station 1, Caminada Pass - Seine - Nearshore 50 meter seine hauls
here produced the highest biomass on July 7, 1971 (5.59 g/m ), lowest
biomass on February 2, 1972 (0.02 g/m ^), and an annual mean biomass of
1.29 g/m^ (Figure 14). Biomass was h ig h e st in the summer, lower in the
fall, lowest in the winter, and increasing in the spring. Abundance was h ig h est in November when 270 fis h (predom inantly Membras m a rtin ic a ) were taken.
S ta tio n 2, Airplane Lake - Trawl - In terms of mean biomass, Air
plane Lake supported the highest trawl biomass of all sampling stations with an annual mean of 1.91 g/m^. The seasonal maximum was 3.46 g/m
on March 26, 1971, and the minimum 0.01 g/m^ on November 23, 1971
(Figure 15). Abundance was a lso h ig h est in March 1971 and lowest in
November 1971.
After the March peak, biomass decreased through the late spring,
increased to a second peak in June, and then f e l l to a w in ter minimum.
The biomass taken in March 1971 and 1972 was n early the same, 3.46 and
3.34 g/m , respectively.
" Station 2, Airplane Lake - Seine - Seine biomass and abundance
in Airplane Lake peaked on March 14, 1972, reaching 12.24 g/m^ (Figure
16) and 10,301 fish. This haul was composed primarily of juvenile 63 2 Brevoortla patronus. Minimum biomass was 2.11 g/m on August 28, 1971.
A second peak on June 14, 1971, was also attributable to large numbers
of B revoortia p atro n u s. Increased biomass on November 4, 1971, was due
to the capture of one large Atlantic sting ray, Dasyatis sabina. On
January 12, 1972, a large series of cyprinodonts were taken which ac
counted for most of the catch. The annual mean seine biomass for Air plane Lake was 6.39 g/m^, the highest of any station.
S ta tio n 2, A irplane Lake - Trammel Net - Trammel n et biomass in
Airplane Lake was highest on April 16, 1971 (4.82 g/m ), lowest on
August 28, 1971 (1.07 g/m^), and had an annual mean of 2.51 g/m^ (Fig ure 17). Fluctuation in biomass was primarily due to a seasonal suc cession in abundance of Leiostomus xanthurus, Brevoortia patronus, Arius fe lls, and Mugil cephalus. Spots and Gulf menhaden were most abundant
in April, sea catfish in May and June, and striped mullet in January and March. Overall abundance was also highest in April 1971 (97 fish), and lowest in January 1972 (6 fish).
Station 3, Bay Lizette - Trawl - Maximum trawl biomass at Station
3 was 8.01 g/m 2 on June 28, 1972, and minimum biomass 0.13 g/m 2 on
January 12, 1972 (Figure 18). The June peak was composed largely of
838 gafftopsail catfish, Bagre marinus, which are summer spawners
(personal observation) and very abundant from June to September. Two distinct peaks are noticeable, one in June and July and the other in
April. Biomass remained very low in the winter of 1971 and increased gradually to the spring peak of 1972. The annual mean biomass was 1.68 g/m . Abundance was highest in July 1971 (2,464 fish) and lowest in
January 1972 (10 f is h ) . 64
Station 3, Bay Llzette - Seine - Biomass was highest on May 25,
1971 (8.09 g/m ^), and lowest on December 16, 1971 (0.36 g/m^) , with an 2 annual mean of 4.60 g/m (Figure 19). The sharp drop in biomass from 2 2 the October to the Decenber trip (6.46 g/m to 0.36 g/m ) may be attri butable to rapidly falling temperatures on the shallow flats at this s ta tio n . Abundance was h ig h e st in la te February 1972 when 869 fish
(mostly A. m itchilli) were taken.
Station 4, Fisherman’s Bay - Trawl - Biomass at this station was 2 h ig h e st on August 28, 1971 (1.79 g/m ) , low est on December 16, 1971 2 2 (0.02 g/m ) , w ith an annual mean of 0.65 g/m (Figure 20). Abundance was also h ig h est in August 19 71 (1,580 fish ) and low est in December
1971 (2 fish). Biomass decreased steadily through the spring of 1971
until July when it began to increase to the August peak. A second peak was observed in November a f te r which biomass decreased to the
December low. Beginning in January 1972, a gradual buildup in biomass occurred to a spring peak in late April after which it decreased through
June. This cyclic pattern appears to be largely due to the seasonal
fluctuation of Anchoa m itchilli (Figure 26) and juvenile sciaenids.
The August peak was composed mostly of bay anchovies which are most
abundant at all stations in August. The gradual increase and decrease
through the early and late spring, respectively, was caused by increas ing and then decreasing biomass of Micropogon undulatus, Leiostomus xanthurus, Bairdiella chrysura, Cynoscion arenarius, and Cynoscion neb ul os us (Table 7).
S tatio n 4, Fisherm an's Bay - Trammel Net - Trammel net biomass a t 2 th is s ta tio n was h ig h e st on October 14, 1971 (5.93 g/m ) , low est on 2 2 February 24, 1972 (2.32 g/m ) , w ith an annual mean of 4.48 g/m
(Figure 21). Large Arlus fells were taken in the warmer months but were not present during December and February. The October peak was composed mainly of large Archosargus probatocephalus, Lelostomus xanthurus. and Arlus felis. Abundance was highest in late July 1971 when 67 fish were taken and lowest in late February 1972 when 9 fish were taken.
Station 5, Oyster Bay - Trawl - The seasonal change in biomass at this station was similar to station 4. Biomass was highest on
April 4, 1972 (4.06 g/m^) and July 7, 1971 (2.78 g/m^), lowest on
February 2, 1972 (0.02 g/m^), w ith an annual mean of 0.83 g/tn^ (Figure
22). Abundance was highest in late July 1971 (1,077 fish) and lowest in early February 1972 (28 fish). The dominant fishes at this station were Anchoa m itchilli and Micropogon undulatus.
Station 5, Oyster Bay - Seine - The change in seasonal seine bio mass at station 5 was very pronounced in that virtually no fish were taken in November and February w hile they were abundant during the warmer months. Peak biomass was 6.42 g/m^ on July 7, 1971, and the lowest biomass 0.02 g/m^ on February 2, 1972 (Figure 23). Abundance was also highest in July 1971 when 606 fish were taken and lowest in la te November 1971 when 2 fis h were caught. Movement of fish e s back into the northern brackish marshes and onto the shallow flats acceler ated from late February until May. The mean biomass at this station was 1.95 g/m^. This is only about one-third of the mean seine biomass of Airplane Lake where the highest biomass was recorded.
Station 6, King's Ridge Oil Canal - Trawl - The peak biomass 66
here was 4.17 g/m2 on March 26, 1971, while the lowest was 0.30 on
December 16, 1971 (Figure 24). A second peak occurred on August 28,
1971 (3.36 g/m2). Abundance was also highest in August 1971 (4,687
fish) and lowest in early July 1971 (48 fish). The dominant fishes
in this habitat were Anchoa m itchilli, juvenile Micropogon undulatus
and Brevoortia patronus, Mugil cephalus, and Lepisosteus spatula.
Numerically, the bay anchovy was overwhelmingly dominant. Its peaks
of abundance in March and August account for the peaks in trawl bio mass at these times. The annual mean biomass of fish at station 6 was
1.13 g/m2 .
Station 6 King*8 Ridge Oil Canal - Trammel Net - Maximum bio mass was 5.92 g/m2 on November 4, 1971, minimum biomass 0.66 g/m2 on
May 17, 1972, and the mean was 2.53 g/m2 (Figure 25). Capture of a
large alligator gar, Lepisosteus spatula;, was responsible for the high
biomass in November. In addition, other large fishes move into oil
canals in cooler weather to reach slightly warmer waters. Striped mullet, Mugil cephalus, were more frequent in the catch in January when colder water temperatures made them somewhat lethargic and more
susceptible to trammel net capture. During warmer months, mullet would
frequently jump over the net. Abundance was highest in January 1972 when 35 fish were caught and lowest in early November 1971 when 7 fish were caught.
Individual Station Biomass and Abundance - Summary - Generally,
biomass was higher at the more saline stations closer to the Gulf.
Station 2, Airplane Lake, had the highest mean trawl and seine biomass
of all stations. Numerical abundance was also highest at station 2 where 32% (30,891) of all fishes were taken. Trammel net biomass 67 was highest at station 4. This may have been true because station 4 was deeper than stations 2 and 6 and greater numbers of large fish such
as Cynoscion nebulosus and Sciaenops ocellata were taken there. I
feel one reason for the higher biomass (trawl and seine), and abundance
at station 2 is the high ratio of marsh-to water interface. Other
studies (Day jet a^., 1972) have indicated the importance of the marsh- water boundary zone in maintaining high estuarine productivity. Kirby
(1971) found production of Spartina alterniflora in this zone in Air
plane Lake the highest that has been reported for a salt marsh (net
production of 2,800 grams dry wt/m^/yr). It is the breakdown of this marsh grass to detritus by microbial and physical processes that pro
vides the food for the majority of the lower trophic levels of the
estuarine food web. Detritus levels in the sediments are highest near
shore. As a consequence, standing crops of organisms are highest in water adjacent to shore. Tidal flushing is the prime mechanism for
transferring the detritus produced in the marsh to the organisms in
the water. Since Airplane Lake is a shallow lagoon of an hour-glass
shape, it had the maximum ratio of rich marsh-water zone of all
s ta tio n s .
Two peaks in biomass occurred--a spring peak in March and April
and a summer peak in July and August (Table 5). Biomass fluctuated
less throughout the year at the upper brackish stations than the lower
saline stations (Table 5). Perhaps this was true because population
lev els flu c tu a te d more in the lower bay due to continual movement be
tween bay and Gulf while in the upper bay, there are two major seasonal
pulses (sp rin g inshore movement and late summer buildup). Maximum
trawl biomass occurring at the two most northerly stations in low 68
Table 5 2 Seasonal Biomass of Fishes (g/m wet weight) Available to
Fishing Gear at Each Station.* Number of Samples in Parenthesis,
Trawl Seine Trammel Net
S ta tio n 0 Maximum 36.96-Feb. Minimum 0 . -Dec. Mean 5.92 (20) s .e ."x 1.67 S ta tio n 1 Maximum 5.25-April 5 .5 9 -July Minimum 0 -June 0.02-Feb. Mean_ 0.91 (22) 1.29 (7) s .e .x .24 2.83 S ta tio n 2 Maximum 3.46-Mar. 12.24-Mar. 4 . 82-A pril Minimum .01-Nov. 2 .11-Aug. 1.07-Aug. Mean_ 1.91 (22) 6.39 (6) 2.51 (7) s .e .x .24 3.06 .58 S ta tio n 3 Maximum 8 .0 1 -June 8.09-May Minimum 0 .1 3 -Jan. 0.36-Dec. Mean, 1.68 ( 22 ) 4.60 (7) s .e .x .24 2.83 S ta tio n 4 Maximum 1 .79-Aug. 5.93 -0 ct. Minimum 0.02-Dec. 2.32-Feb. Mean 0.65 (22) 4.48 (7) s .e .x .24 .58 S ta tio n 5 Maximum 4.06-April 6.42-July Minimum 0.02-Feb. 0.02-Feb. Mean .83 (22) 1.95 (7) s .e .x .24 2.83 S ta tio n 6 Maximum 4 . 17-Mar. 5.92-Nov. Minimum 0.30-Dec. 0 .66-May Mean 1.13 (22) 2.53 (6) s .e .x .24 .62
★Standard error of the means (s.e.x) are also given. 69
salinity water (station 5 and 6) was in March and April when postlarval and juvenile fishes were most abundant. As these fishes moved Gulfward
in the late spring, biomass in the more northern low salinity areas began to drop but increased in the southern more saline areas. Biomass was highest at stations 3 and 4 in June and August, respectively. Bio mass was lowest a t most s ta tio n s from November to February. Trammel net biomass was highest at station 2 in April and at station 4 and 6 in
October and November 1971, respectively. I believe the latter occurrence was due to movement of larger fishes into deeper channels and oil canals
(such as station 4 and 6) from shallow surrounding marshes for escape ment from low water temperatures. Depth at station 6 averaged 2 m and was slightly warmer in winter than water in the shallow marshes. From
October to February, water temperatures were generally 2 to 4°C higher at station 6 than at other stations (Table 3). Standard error of the mean biomass at each station for each gear was calculated (Table 5).
The larger standard error of the seine and trammel net means indicates
that less reliability can be placed on these data.
Seine biomass was from 2 to 3 times higher than trawl biomass at
stations sampled with both kinds of gear. It is difficult to determine
if this was due solely to gear efficiency or because biomass was naturally higher along the shorelines where the seine was used. This pattern was probably due to a combination of increased gear efficiency
and higher biomass along the shoreline.
In terms of numerical abundance, the mean number of fish per m
taken by the trawl reached a maximum of 1.32/m2 at station 6 (Table 6).
The numbers of fish per m2 available to the seine was highest at Table 6
Summary of Station Biomass, Abundance and Species Composition Data
T otal Num. Mean Num. Mean Total Weight . Mean Biomass Mean Num S tatio n Fish per Sample* Num. /m F ish (g) g/m2 Species
1-T 2009 91 (121.8) .11 16688.1 0.91 4 2-T 15036 683 " .82 34908.5 1.91 9 3-T 8798 400 " .48 30761.1 1.68 9 4-T 4987 227 " .27 11882.8 0.65 7 5-T 8790 400 " .48 15184.7 0.83 6 6-T 24243 1102 " 1.32 20783.3 1.13 6
0-S 9785 489 (351.6 .64 89982.9 5.92 7 1-S 1099 157 (594.3) .21 6842.6 1.29 8 2-S 15636 2606 (641.8) 3.43 29146.5 6.39 14 3-S 2937 420 (594.3) .55 24471.3 4.60 14 5-S 1635 234 (594.3) .31 10374.4 1.95 11
2-Tr 219 31 (4.8) .02 23317.7 2.51 4 4-Tr 212 30 (4.8) .02 41661.9 4.48 7 6-Tr 100 17 (5.2) .01 20113.9 2.53 5
T = Trawl S = Seine Tr = Trammel Net
*Standard error of the mean given in parenthesis. 71
o Station 2, Airplane Lake, where a mean number of 3.43 fish per m was caught. This was the highest numerical density of any station and any gear. Numbers of fish per m^ available to the trammel net were quite low, averaging about .02/m'. This was because the trammel net caught fewer fish than the other gear, though the fish were of a
larger size.
Statistical analysis indicated there was a highly significant difference in trawl biomass between trips and trawl numbers between
trips and stations (Table 24 in Appendix). Analysis of seine and
trammel net biomass and numbers did not show a statistical degree of difference (probably because not enough samples were taken).
Distinct trends and patterns were noted in biomass and numbers taken with the seine and trammel net even though it was not possible to
show s t a t i s t i c a l l y .
It is emphasized again that these estimates are minimal. Gear
selectivity, net avoidance, and differing species behavior patterns act together to produce estimates which are on the low side. No effort was made to sample on a certain tidal stage. It is conceivable
that biomass would have been higher or lower if sampling were done consistently on a definite tidal stage. Sampling was during daylight hours because of difficulty in navigating the marsh at night.
Certain species become more susceptable to capture at night because
of changes in behavior or inability to see the gear. No estimates were made of fishing or natural mortality. Biomass was taken as the
fish weight per unit area (g/m ) at one point in time and since 72 estuarine fishes are only transitional occupants of a certain area and less than 100% of the fish are captured, it is obvious that their true levels of biomass have been underestimated.
Importance of Nearshore Zone and Marsh-Water Interface
It has already been pointed out that the nearshore fringing marsh-water zone supports higher biomass and is a key factor in estuarine productivity. Two short term projects done incidental to my study tend to support this. During a mark-recapture experiment at Station 2, Airplane Lake, from May 22-25, 1972, twelve 200 meter parallel trawl drags were made at increasing distances from shore for the purpose of capturing spot, Leiostomus xanthurus, for marking. A distinct spatial zonation was observed with greater numbers and bio mass being taken immediately adjacent to both shorelines. A gradual decrease in numbers and biomass occurred in the collections at increasing distance from shore. This pattern held true for other species caught in addition to spot. A much greater volume of organic detritus was also noted near the shorelines.
The second project suggesting higher nearshore biomass was a study of two small ponds near Airplane Lake in October 1971 using
Antimycin, a fish toxicant. Two types of ponds were sampled. One 2 was a blind or isolated pond with an area of 224 m , a depth of .12 m to .3 m and a soft silty-clay bottom with much Spartina detritus. o The other was slightly smaller (193 m ) but somewhat deeper with a depth of .3-.45 m and a firmer clay bottom. The latter pond was connected by a tidal creek to a larger bayou. The purpose of this study was to determine species composition, abundance, and biomass In the shallow pond habitat of the interior marsh where sampling was not possible with the primary gear. Nine species were collected in the blind pond, the majority of which were fishes of the family
Cyprinodontidae and Mugilidae. Fishes taken were representative of those along shallow vegetated shorelines. Ten species were taken in . ' • * the deeper connected pond, none of which were cyprinodonts. The predominant species were Anchoa mitchilli, Cynoscion nebulbsus,
Cynoscion arenarius, Menidia beryllina, Paralichthys lethostigma, and Strongylura marina.
Both ponds had much greater biomass than my regular sampling stations which by comparison are in more open and deeper bay areas. o Highest biomass was in the isolated pond (46.1 g/m ) and lowest in the connected pond (13.8 g/m ). This is a minimal estimate of the biomass present in these ponds because it was impossible to net all fish killed due to delayed death of some species. Many others were lost to diving gulls and blue crabs which ate the fishes before they could be netted. From the number observed subsequent to collection and those lost to birds and crabs, probably only about one-quarter of the fishes present were collected. Regardless of the exact biomass present in these ponds, the high standing crop of these areas was evident. The higher biomass in these small ponds may be due partially to gear selectivity. The trawl, seine and trammel net are selective for certain species of fish while Antimycin is effective on a wider number of species. Finucane (1969) reported 38 species killed by
Antimycin in Tampa Bay, Florida. These small marsh ponds may, however, be naturally more productive than the deeper bay areas. They have a 74 greater surface area of marsh-water interface. This peripheral zone produces the majority of organic detritus found in estuarine waters.
Detritus is the major food source of many consumers in the estuary.
Such high productivity in the marsh ponds and shallow nearshore areas may be a clue as to why the Caminada-Barataria Bay system pro duces the highest fishery yield on the Louisiana coast. When com pared to the St. Bernard-Breton Sound area which is the least pro ductive hydrologic unit on the Louisiana coast in terms of lbs/acre fishery harvest (Lindall et ad., 1971), the Barataria system is com posed of nearly twice the amount of natural marsh and only about one-tenth as much open water in the form of bays and sounds (Chabreck,
1970). The Barataria system therefore has a much greater area of shoreline and marsh-water interface. Differences in salinities and inflow of nutrients and fresh water from the Mississippi River may also play a part in the differing fishery yield. The St. Bernard system has an average salinity 7 °/oo lower than the Barataria Bay area (Barrett, 1971) and does not receive near the volume of fresh water flow from the Mississippi River. The Pearl River dilutes salinities considerably in the St. Bernard delta system (Barrett,
1971). Rounsefell (1971), among others, has pointed out the fer tility derived from the combination of freshwater from the Missis sippi River and saltwater from the Gulf. The area around the mouth of the Mississippi River and westward to the Texas coast has annually produced about one billion pounds of menhaden and industrial fish fo r the la s t sev eral years (U.S. Department of Commerce, 1971). The entire Gulf fishery is centered around this "fertile fisheries 75
crescent" (Gunter, 1963) and it is among the world's most productive
fishery regions.
Biomass, Abundance and Distribution of Dominant Species
A total of 97,223 fishes weighing 376.1 kilograms was taken in
this study (Table 8). These fishes had a combined mean biomass of
16.44 g/m . The fivedominant species in terms of total number and
weight taken were Anchoa m itchilli, Brevoortia patronus, Leiostomus
xanthurus, Micropogon undulatus, and Arius felis. These five species made up 83% of the total number and 41% of the total weight of fish
taken. Dunham (1972) found that Anchoa m itchilli, Leiostomus xanthurus,
Micropogon undulatus and B revoortia patronus made up 92.3% of the to ta l
number of fish caught in a 3 year trawl study of Barataria Bay. In my study, these four species were among the 10 species taken at all
stations and the 16 species taken by all three types of gear. Only
two species, Anchoa m itchilli and Micropogon undulatus, were taken on
every sampling trip during the study. Seasonal biomass and abundance
of the most frequently taken species are presented in Table 7 and the
total number and weight, mean biomass, length range, salinity and
temperature ranges, location and method of capture for all species
is presented in Table 8.
Anchoa m itchilli - The bay anchovy was numerically the most
abundant fish in this study, comprising 54.1% of all fish taken and
second in terms of weight taken with 9.1% of the total biomass. A
total of 52,633 bay anchovies were caught, 46,721 with the trawl and
5,911 with the seine. These fish weighed 34.2 kilograms and had an 2 annual mean biomass of .29 g/m . Bay anchovies were taken on every 5/25/71 6/14/71 7/7/71 7/28/71 8/28/71
Anchoa m itc h illi 1248(.15) 1065(.13) . 835(.09) 55 68(.83) 7493(.70) Brevoortia patronus 12(.04) 4438(.96) 247(.25) 10(.03) 14(.03) Leinstomas x a n t h u r u s 45(.09) 27(.05) 8 ( .01) 11(.05) 10(.12) Micropogon undulatus 305(.31) 56(.10) 47(.14) 28(.10) 10(.08) Membras m artinica 3 ( .01) 2696(6.29) -- __ A r i u s f e l l s 64(.76) 32(.29) 20(.28) 43(.51) 1288(.79) Chlor.oscQmbr.us chry.surus — 3(.0001) 136(.09) 8(.006) 1390(1.91) Anchoa heosetus — 82(.01) 1207(.34) 112(.08) 71(.05) Bagre marinus — -- 8 ( .04) 101(.18) 23(.05) Bairdiella chrvsura 2(.008) — 4(.001) 7(.005) 1 1(.02) Menidia bervllina 154(.32) 27(.02) 28(.06) 12(.02) 7(.02) Eundulus erandis — 2 ( .002) — Cynoscion arenarius 75(.04) 63(.06) 61(.02) 69(.04) 8 ( .02) Onisthonema oelinum -- -- 367(.12) 1 (.005) 1 ( .008) S.phoeroides parvus 8 ( .006) 1 9(.009) 3 0 (.01) 2 8(.01) 3 6 (.02) Chaetodipterus faber — 2(.001) 21(.005) 77(.09) 27(.04) Alosa chr y sochioris —— 260(.21) 1 ( .0005) Citharichthys spilopterus 2(.001) 55(.03) 9 ( .006) 4(.003) 2 ( .003) Eundulus aim ilis 2 ( .02) — 1 ( .003) — Mugil cephalus 4 ( .06) 2 1 (.53) 1 8(.40) 5 ( .18) 4 ( .20) Trichiurus lepturus 3(.007) ------Symphurus plagiusa 2 ( .002) 8 ( .01) 3( .003) 3( .002) 3(.0008) Gobionellus boleosoma ------Menticirrhus americanus 6 3 (.23) -- 1(.0001) 1 ( .0003) 6 ( .03) Anchoa lyolepis -- 103(.09) ---- Larimus fasciatus — 83(.03) -- -- ■ -- Cynoscion nebulos.ua 1(.042) 1(.06) — 4 ( . 14) 2(.004) Table
Numerical Abundance and Seasonal Biomass of At All S tations w ith Combined Gear
8/28/71 9/21/71 10/14/71 11/4/71 11/23/71 12/16/71 1/12/72 2/2/
7493(.70) 927(.09) 1646(.20) 2589(.19) 558(.07) 1116(.13) 1240(.11) 1245 ( 14 (.03) 31(.05) 6(.03) 5 6 (.06) 207(.15) 65 ( 10(.12) “ - 1 6 (.18) 4 3 (.29) 8(.06) 1(.006) 48( .005) 28 ( 10(.08) 8(.04) 2(.01) 46(.01) 164(.004) 673(.02) 255(.02) 210( -- 1470(3.20) 135(.67) 5 ( .009) 183(.61) - -- - . 1288(.79) 98(.07) 129(.53) 218(.26) 2(.004) 5(.12) 4 ( . 17) -- 1390(1.91) — _ _ — 71(.05) 2 ( .001) 1(.001) 1 (.0002) 23(.05) 30(.12) 11(.04) •» «• •• •> •» •» 11(.02) 14(.02) 3 ( .008) 7(.01) 11(.03) 1(.005) 1(.003) 591 ( 7(.02) 6(.01) 12(.03) 6(.006) 1(.003) (•005) 5 9 (.18) •> 1( " •" 520(1.82) __ 8 ( .02) 45(.02) 18(.01) 1 8 (.03) 3 ( .003) — -- 1 ( .008) -- _ M _ _ 3 6 (.02) 15(.01) 40(.03) 41(.03) 38(.04) - _ 2 ( .002) mm m. 27(.04) 18(.04) 137(.28) 24(.06) 1 (.002) . _ - - - - ) 5 ( . 002) — _ - 4( 2(.003) 6 ( .01) 12(.01) 3 2 (.02) 1 (.0004) 6 ( .0007) 8 ( .001) 2( •> — — — — 197(.93) 4 ( •20) 13(.42) 6 ( .36) 9(.23) 5(.04) 8 ( •14) 20 (.59) -- 1 0(.02) 1 ( .004) 9 ( .05) - 3(.0008) 3(.009) 6(.009) 3 9 (.04) 9(.006) 2(.0008) 2(.0007) 21 — — 9 ( .001) 2 ( .0001) 13(.0008) 37(.003) 24 ( 4 ( .03) )03) 6(.03) (9.03) 3(.01) 4(.02) ------
2(.004) 2(.003) 3(.02) 5(.03) 10(.05) 9 (.04) 5 (.0.2) 5i
i Table 7 asonal Biomass of the Most Frequently Caught Species Taken tfith Combined Gear. Biomass in P arenthesis in g/m^.
1/12/72 2/2/72 2/24/72 3/14/72 4/4/72 4/29/72 5/17/72 6/7/72
1240(.11) 1245(.14) 1931(.35) 5079(.66) 4555(.44) 1081(.22) 1300(.13) 972(.0£ 207(.15) 65(.004) 175(.028) 7946(.70) 861(.04) 57(.19) 3 1 (.08) 308(.0( 48(.005) 28(.035) 571(.04) 2454(.35) 535(.27) 533(.44) 451(. 31) 4 8 (.Of 255(.02) 210(.03) 540(.08) 476(.07) 608(.32) 705(.66) 397(.38) 108(. IS -- — -- 19(.09) 1 (.007) — _ _ 4C-17) — 36(.39) 3 ( •07) 4 8 (.78) 9 ( . 16) 48C.59) 5 3 (.0 ‘
— — —------23(.004) 2 8 (.01
1c-003) 591(4.2) 15(. 07) 1(.01) 11(.06) 2 6 (.15) 3 7(.02) 136(.0) 5 9(.18) 1 (.006) 14 (.04) 7 8(.16) 22(.03) 200(.40) 5(.02) i6 (.o : 520(1.82) -- -- 9 ( .04) -- — — — 2 ( .0006) 7(.001) 14(.007) 3 i(.o :
2 ( .002) -- 24(.02) -- — 1(.0001) 8 ( .003) 6(.0(
— 4 ( .08) ---- _ _ 1(.0( 8 ( .001) 2(.0004) 16(.002) 2 ( .0001) -- 2 ( .0006) 3 4 (.02) 8(.0( 19 7(.93) -- 1 (.008) _ . 2 0 (.59) -- 10(.12) 16(.17) 1 ( •01) 1 0 (.25) 2 (.03) 6 ( . If — -- 2 ( .003) 1(.002) 88(.21) 12(.02) 8 ( .008) 9(.0i 2 ( .0007) 2(.0004) 39(.03) 9(.0005) 4(.007) 1 (.002) 9 ( .02) 37(.003) 24(.003) -- 6 ( .0006) 2 ( .0001) — - — • - 1(.01) 2 ( . 01) 5(.09) - - : : • mm w
5 (.0.2) 5 ( .06) 3 ( .007) 5 ( .13) 1 (.008) 4 ( .11) 3 ( .05) :: 7 6
ie Most Frequently Caught Species Taken Biomass in Parenthesis in g/m^.
2/24/72 3/14/72 4/4/72 4/29/72 5/17/72 6/7/72 6/28/72
4) 1931(.35) 5079(.66) 4555(.44) 1081(.22) 1300(.13) 972(.08) 3555(.29) 104) 175(.028) 7946(.70) 861(.04) 5 7 (.19) 31(.08) 308(.06) 3 ( .001) 135) 5 71(.04) 2454(.35) 535(.27) 533(.44) 4 51(.31) 48(.06) 58(.10) >3) 540(.08) 476(.07) 608(.32) 705(.66) 397(.38) 108(.19) 27(.10) -- 19(.09) 1 (.007) — 36(.39) 3(.07) 48(.78) 9 (.16) 4 8 (.59) 53(.09) 37(.67) ------1 (.004) — 23(.004) 2 8 (.01) 1 (.0003) -- -- 838(.82) 2) 15(.07) 1(.01) 11(.06) 2 6 (.15) 3 7 (.02) 136(.07) 14(.006) )06) 14(.04) 78(.16) 22(.03) 200(.40) 5 ( .02) 16(.03) 146(.25) -- 9 ( .04) — -- -- /-\ i-H o P-* 1 o 2 ( .0006) 14(.007) 31(.03) 10(.02) 1
24(.02) -- 1(.0001) 8 ( .003) 6 ( .001) 2 3(.01) -- -- 2 ( .001) )8) ------1 (.002) 5 ( .009) )004) 16(.002) 2 ( .0001) 2 ( .0006) 3 4 (.02) 8 ( .005) 1 (.0007) -- 1 ( .008) —-- 1 0 (.12) 16(.17) i( .o i ) 10(.25) 2 ( .03) 6 ( .16) 7(.11) 2 ( .003) 1 ( .002) 8 8 (.21) 12(.02). 8 ( .008) 9 ( .02) 8 ( .007) 3004) 3 9 (.03) 9(.0005) 4 ( .007) 1 (.002) 9 ( .02) -- -- 303) 6 ( .0006) 2 ( .0001) — -- i( .o i ) 2( • 01) 5(.09) ** “ “ "■ : : i
36) 3 ( .007) 5 ( •13) 1 (.008) 4 ( .11) 3 ( .05) 2 ( •10) 77
sampling trip and at all stations.
Two distinct peaks in biomass occurred (Figure 26), one in July
(.83 g/m^) and the other in March (.66 g/m^). Abundance was highest
in la te August 1971 and lowest in la te November 1971. These peaks
coincided with the occurrence of the smallest juveniles; therefore bay
anchovies apparently have two spawning peaks, in mid summer and in the
spring. Spawning seems to occur throughout the year as reported by
Perret (1971). Little progression in length frequency curves can be
seen as specimens less than 30 mm were taken every month and little
"apparent" growth results. Bay anchovies were taken ranging from 16
to 92 mm total length. Smaller specimens were taken at the low
salinity stations while the larger individuals of the species were
taken in more saline waters. The usage of low salinity brackish marshes by the juvenile forms of the bay anchovy and many other estuarine dependent fishes constitutes the designation of this area
as a nursery ground.
The bay anchovy is a resident estuarine fish completing its
entire life cycle in inshore waters. Though very abundant, the bay
anchovy is not utilized commercially. The bay anchovy's abundance is
due to complete adaptation to estuarine conditions. It is euryhaline
and eurythermal and was found at all salinities (.2 to 34 °/oo) and
temperatures (12 to 35°C) recorded in this study. Although the bay
anchovy was taken through a wide salinity range, it was most abundant
at salinities between 5 and 10 °/oo. Thirty-nine percent of all bay
anchovies taken were caught at station 6.
Gunter (1941) felt the bay anchovy was the most abundant fish Figure 26. Seasonal biomass and number of Anchoa m itchilli taken with combined gear at all stations, March 1971 - June 1972. Number of Anchoa mitchllli per hectare x 1000 12 10 8 4 /641 57 /5 /4 / 72 /8 2II0/1 /112 21 2 / 22 3 4 / 42 51 67 6/28 6/7 5/17 4/29 4/4 3/ 1414 / I 0 1/23I/41 I 2/24 12/16 I I /2 12 9 / 2/2 8/28 7/28 7/7 6/14 5/25 5/7 4/16 3/26 6 l I °l— 2 ----- I I ! I I I 1 -1971. ___ 1 ___ I ___ I ___ 1 ___ Date 1 1 I 1 I 1 I 1 1 I I 1 1 1 1 1 Number/ha. ims kg/ha. Biomass 1972- — 1.0
Biomass kilograms per hectare x 10 (or grams per meter -<} 00 79
in estuaries of the Gulf Coast, both numerically and in terms of
species mass. My data indicate bay anchovies were first numerically
but second in terms of species mass. Herke (1971) found the bay
anchovy first in numbers and weight. In most other estuarine studies
in Louisiana, the bay anchovy was the most abundant fish taken, i.e.,
Norden (1966), Fox and Mock (1968) and Perret (1971).
Brevoortia patronus - A total of 14,782 Gulf menhaden were taken
in this study, 2,466 by trawl, 12,192 by seine and 124 with the
trammel net. It was the most abundant fish in the seine samples and
comprised 15.2% of the total number and 6.1% of the total biomass of
fish taken. Although Gulf menhaden were taken through most of the year, two distinct peaks in abundance and biomass occurred. These
peaks were in June 1971, when 4,438 (.96 g/m^) were taken and March
1972, when 7,946 (.70 g/m^) were taken (Figure 27). The mean biomass 2 of menhaden caught on any one sampling trip was .15 g/m .
This fish is dependent on both inshore and offshore waters at
different phases of its life cycle. After being spawned in Gulf
neritic waters from October to March (Turner, 1969), the postlarval
move in through the tidal passes into shallow estuarine waters where
they metamorphose into prejuveniles. This transition occurs at 25-30
mm total length. The prejuveniles gradually increase in girth and are
classified as juveniles after reaching approximately 40 mm. Inshore
recruitment was noted from mid January to early April 1972, when post
larvae were first taken in the low salinities at stations 5 and 6.
Most menhaden spend from five to eight months in inshore waters moving
offshore in the summer and early fall. In June, large schools of Figure 27. Seasonal biomass and number of Brevoortia patronus taken with combined gear at all stations, March 1971 - June 1972. Number of Brevoortia patronus per hectare x 1000 /641 57 /5 /4 / 72 82 92 1/41/ I12 21 2 / 22 31 44 /9 /7 / 6/28 6/7 9/21 4/29 5/17 10/14 8/28 7/28 11/4 4/4 I 1/23 7/7 3/14 2/2412/16 6/14 5/25 2/2 I 12 5/7 3/26/ 4/16 1971 Biomass kg/ha. Number/ha. Date \ V 1972-
Biomass kilograms per hectare x 10 (or grams per meter 0 0 O 81
Gulf menhaden were observed migrating offshore through Caminada Pass.
Lindall et a_l. (1971) reported that some menhaden may overwinter in
inshore waters. My study supports this for a few large menhaden were
taken in the winter months.
A very spotty and irregular distribution was noted for this
species. About half of the specimens taken were caught with the seine
at one station on one sampling trip (Airplane Lake, March 1972).
Through the entire study, 83.7% of all menhaden were taken in Airplane
Lake. Catches were very low from late July to February. No menhaden were taken on November 23 and December 16, 1971. I believ e th is
situation was due to the fact that Gulf menhaden are pelagic school
ing fish and capture was probably the result of chance sampling of
mobile populations. Hoese et al. (1968) reported a significant in
crease in catch at night of this species due to an unusual pattern
of behavior. Hoese reported Gulf menhaden move to the bottom at
night while during the day they school at the surface. All of my
samples were during daylight hours so the Gulf menhaden is probably
much more abundant in the study area than tty data indicate.
Gulf menhaden were taken over wide ranges of salinity (.2 to
31 °/oo) and temperature (12 to 35°C). They were most abundant at
salinities of 20 to 25 °/oo. Although taken at all stations, they were most abundant at stations 2 and 6.
The size range for specimens taken was from 22 to 261 mm total
length. If the cod end of my trawl had had finer mesh, postlarvae
of a smaller size would probably have been picked up in December.
Turner (1969) recorded inshore movement of the p o stlarv ae in December in the eastern Gulf. The smallest specimen (22 mm) was taken at a salinity of 15 °/oo and the largest (261 mm) at 4 °/oo. Contrary to other studies, i.e. Perret (1971), in which the largest specimens were reported from high salinities, the opposite situation was found here. There was a gradual increase in mean length toward the lower
salinities for specimens over approximately 100 mm. For example, in specimens taken with the trammel net at stations 2, 4, and 6, the
largest fish taken at each station increased from 216 to 247 to 261 mm, respectively. In contrast, for prejuveniles and juveniles (less than 100 mm), the opposite pattern of distribution existed. The smaller individuals of this group were found in low salinities and the larger at more saline areas. An example of this pattern was observed on the March 15, 1972, trip when the mean length of specimens taken at stations 2, 5, and 6 decreased from 37 to 35 to 29 mm, respectively. This particular cohort of prejuveniles was gradually moving up to fresher waters and this pattern may have been due to a
"leap-frog" effect of schools of smaller fishes moving rapidly up the bay. The rev erse d is tr ib u tio n of specimens over 100 mm may be due to a preference of larger individuals for lower salinities. Larger menhaden are herbivores and Cronin and Manseuti (1971) report that in the summer in some estuaries phytoplankton crops are most dense near the surface in low salinity areas. Larger menhaden may there fore be found in lower salinity because of their food preferences.
There is also the possibility that I could have been sampling
transients which were moving either up or down the bay.
Age and growth rates have been reported by Suttkus and 83
Sundararaj (1961) for spawning populations of Gulf menhaden off the mouth of the Mississippi River. They found 3 age groups in this
population but 85% were Age Group II fish. On the basis of scale
analysis, they found Age Group I fish had a mean total length of
183 mm, Age Group I I fis h a mean to t a l length of 203 mm, and Age
Group I I I fis h a mean to t a l length of 220 mm.
The Gulf menhaden supports the largest commercial fishery in
Louisiana with over one billion pounds being harvested annually by
offshore purse seiners. It accounts for nearly 85% of the total
Louisiana fishery harvest (Lindall et a l., 1971) and Louisiana pro duces 70% of the total United States menhaden landings (Chapoton,
1971). The fishery for Gulf menhaden occurs from April to October.
Lindall (op. cit.) also found that the coastal region offshore from
Barataria Bay yielded the greatest harvest of menhaden along the
Louisiana coast yielding nearly as much as all other offshore systems combined.
Leiostomus xanthurus - The spot was the most abundant member of the Sciaenidae. It ranked third in abundance representing 6.0% of the total number of fish caught and seventh in biomass composing 5.4% of the total weight of fish (Table 8). A total of 5,786 spot were taken
(Table 8), 5,112 with the trawl, 560 with the seine, and 114 with the trammel net.
Spot were most abundant in March, April and May but were taken every month except September. Peak levels of biomass were .35 g/m^
in March and .44 g/m^ in April (Figure 28). After this spring peak, numbers and biomass decreased rapidly. The annual mean biomass for Figure 28. Seasonal biomass and number of Leiostomus xanthurus taken with combined gear at all stations, March 1971 - June 1972. © o Number of Leiostomus xanthurus per hectare X /641 '/ 52 61 77 /8 /8 /1 01 1/ 12 1/6/2 / 22 31 44 /9 /7 / 6/28 6/7 5/17 4/29 4/4 3/14 2/24 2/2 9/21 10/14 11/4 12/161/12 11/23 8/28 7/28 7/7 6/14 5/25 '5/7 3/264/16 1 7--1972 -1971- Biomass kg/ha. — — Number/ha. Date 3129 f
Biomass kilograms per hectare x 10 (or grams per meter' 85 2 spot was .28 g/m .
This fish is estuarine dependent, spawning offshore from the tidal passes in January and February (Gunter, 1938) and moving into the bays as postlarvae from January to March. Spot were first picked up at a length of 18 mm in January and February 1972 at station 6.
Offshore emigration began in May and June when spot were 75-88 mm and proceeded until September when no spot were taken. Apparently all
Age Class 0 fish had emigrated offshore by September and only fish in older age classes remained inshore. Sundararaj (1960) found through scale analysis that 1 year old spot in Lake Pontchartrain,
Louisiana, had a modal length of 142 mm.
Spot were most common at station 2 where 90% of the total num ber were taken. Although taken in salinities from 1.5 to 31 °/oo and at all stations, they were more abundant at about 10 °/oo. They were taken at temperatures ranging from 12 to 35°C but were most abundant at from 20 to 23°C. The length range of specimens was from 18 to
228 mm. Age c la ss 0 spot were sm aller a t low s a l i n i t i e s and larg er at higher salinities. This did not hold true for Age Class I and II spot. Total length increased for these fishes at decreasing salinities.
For example, largest spots taken with the seine and trawl from sta tions 0-6 were of the following lengths: 175, 180, 185, 186, 194, 202, and 220 mm, respectively. The largest spot taken at station 2, 4, and 6 w ith the trammel n et were 185, 210 and 228 mm, re sp e c tiv e ly .
Oddly, both the largest and the smallest spot taken were from station
6. This unusual distribution is hard to explain. It was also noted for Gulf menhaden and somewhat for Atlantic croaker. Factors other 86
than salinity preference seem to be Involved. Subtle changes in food
habits and food availability, bottom preference, and evolutionary behavior patterns may be implicated.
Spot show a general increase in abundance from west to east along
the northern Gulf of Mexico (Nelson, 1969). In Texas, croaker are much more abundant than spot (Gunter, 1945) while in Florida, spot
outnumber croaker substantially (Gunter and Hall, 1965). In my study,
spot were slightly more numerous than croaker (Table 8).
Spot are important in the industrial bottomfishery along the
northern Gulf Coast. Spot are classified as "trash" fish and used in
pet food. Roithmayr (1965) found that spot comprised 13% of the total
industrial catch east of the Mississippi River, second only to croaker.
Lindall et al. (1971) reported that spot were the third most important
commercial fish in the Louisiana landings behind Gulf menhaden and
Atlantic croaker. Dunham (1972) reported that spot comprised 5.3% by weight of the industrial bottomfish landed in Louisiana.
Micropogon undulatus - The Atlantic croaker was fourth in abun
dance representing 5.5% of the total number and fifth in biomass with
6.1% of the total weight. A total of 5,300 were caught (Table 8),
4,996 with the trawl, 282 with the seine and 22 with the trammel net.
Croakers were taken on every sampling trip and at all stations.
The peak in seasonal abundance was in April while biomass was
highest in May (.71 g/m^). Abundance was lowest in October (before 2 recruitm ent began) and biomass a t a minimum in November (.01 g/m ).
Figure 29 represents the seasonal variation in number, biomass and
production of the Atlantic croaker. Details on calculation of croaker Figure 29. Seasonal production, biomass and number of Micropogon undulatus taken with combined gear at all stations, July 1971 - June 1972. Number of Micropogon undulatus per hectare x 100
O hJ Jh O n 00 o N>
SM 00
ro
O'
-o M N>
H)
I a I
N) 0 0 UJ in
Production grams wet wt/meter /trip
Biomass kilograms/hectare x 10 (or grams/meter^)
IS production will be discussed in a later section. The mean annual 2 biomass of croakers was .21 g/m .
The croaker spawns offshore from the bays near the tidal passes
(Pearson, 1929) from October to March with a peak in November. Suttkus
(1954) noted that spawning and recruitment in Lake Pontchartrain,
Louisiana, occurred from October to January. Herke (1971) reported recruitment from October to May at Marsh Island, Louisiana. Inshore recruitment in my study started in November and continued until April.
P o s tla rv a l croakers were f i r s t taken on November 4, 1971, a t a length of 11 mm at station 2. Movement inshore seemed to occur in "waves" or cohorts. These waves can be followed partially by reference to changes
in modal length on length frequency histograms. After spending 6 to 8 months in the estuary, offshore emigration began in May at a mean
length of 89 mm and continued until November. Croaker populations continued to decrease until inshore movement by postlarvae began in
November.
The croaker is a euryhaline species and has been recorded from
freshwater (Nelson, 1969) to hypersaline waters of 75 °/oo (Simmons,
1957). I took specimens in salinities from 0.2 to 35 °/oo and tem peratures from 12 to 35°C. They were most abundant at station 6 where salinities averaged 8 °/oo and temperatures ranged from 18-26°C.
Thirty-six percent of all croakers were taken at this station.
Croakers were taken ranging from 11 to 241 mm. From November to
February, only Age Class 0 croakers (less than 150 mm) were taken in the bay. Apparently low water temperatures drove older fish out into
the Gulf. A number of workers have noted that juvenile croakers can 89
tolerate lower temperatures than the adults (e.g. Gunter, 1945).
Croakers In Age Classes I and II were taken only from February to
November.
There appears to be a relation between size and salinity for Age
Class 0 croakers but little relation for older individuals. Age Class
0 croakers move into low salinity marshes as they are recruited from
offshore. As growth increases they apparently move down the bay to
higher salinities. This size gradation is particularly noticeable
after May when emigration has begun and the larger individuals of
each size group are migrating offshore. Through age and growth anal
ysis (reported in a later section), it was determined that only 29 of
5,300 croakers were one year or older. Young-of-the-year croakers moved offshore from May through the winter months. Wallace (1941)
noted that 1 year old fish return to inshore waters in the spring and
remain u n t i l they approach m atu rity in la te summer. My data supports
Wallace (02 . c it.) in that Age Class I croakers were taken in the bay
only from February to November after which they apparently move off
shore. Spawning of two year old fish occurs after this offshore move ment (Gunter, 1945). Avault et al. (1969) and Herke (1971) report
spawning at one year of age. Avault's data was based on growth in
managed ponds which may not be indicative of natural conditions. I
feel Herke overestimated growth rates and what he called one year old
fish were actually two years old. Age Class I croakers were taken
in a l l s a l i n i t i e s and showed l i t t l e r e la tio n to s a lin ity . I f such a
relationship does exist, it seems to be a preference for lower salini
ties. The largest croakers taken in this study were from station 6 where lowest salinity occurred. Parker (1971) observed that croakers
larger than 130 mm in Galveston Bay were more abundant in lower salinities. As previously mentioned, the size distribution of fishes
in estuaries is affected by at least several interacting factors. No one factor can be assigned as the causative one. Herke (1971) stated that distribution and emigration were caused by a combination of factors, none of which were dominant. The fact that there is a
correspondence between increasing size and increasing salinity does not necessarily imply that salinity is the sole governing factor. I feel that this relation between size and salinity is more of a coincidence than a cause and effect relationship. Most estuarine and estuarine-dependent fishes possess a degree of euryhalinity which allows them to survive over a wide range of salinity. Evolutionary behavior patterns have developed in the life history of these fishes in which they move Gulfward from the low salinity nursery grounds as they grow and m ature. The fa c t th a t th ere is an apparent re la tio n s h ip to salinity for Age Class 0 croakers but little or none for Age Class
I and II croakers leads me to believe that the size-salinity relation ship exists only when young croakers are emigrating down the estuary prior to their first spawning. There are of course optimal salinities at which best growth and survival occur but salinity in itself is probably not the only cause of the size gradation of many estuarine fis h e s .
The croaker is second only to Gulf menhaden in terms of commer cial importance. It comprises 56% of the commercial bottomfish land ings in the Gulf east of the mouth of the Mississippi River (Roithmayr, 91
1965). Lindall et: al. (1971) reported an average yearly harvest of
23.7 million pounds in Louisiana from which 4.9 million pounds came from Barataria Bay. Atlantic croakers are of considerable importance as a sport fish and are taken in large numbers by fishermen along the
entire Louisiana coast.
Arius felis - The sea catfish was first in terms of fish weight
(14.0% of the total) but sixth numerically (2.2% of the total). There were 2,169 caught, 1,149 with the trawl, 932 with the seine, and 88 2 with the trammel net. Biomass was highest in August (.79 g/m ) and 2 April (.78 g/m ) and lowest in February when no sea catfish were taken
(Figure 30). The mean biomass was .63 g/m . Sea catfish were taken every month except February but seasonal abundance was highest in
August which is near the end of the spawning season. Numbers and bio mass decreased rapidly through the fall as sea catfish moved offshore for overwintering. Inshore movement began again in late February reaching a spring peak in April and May.
Spawning occurs both inshore and offshore from May to September.
Ward (1957) reported eggbrooding males in Biloxi Bay, Mississippi, from May to August. I noted males carrying eggs at station 5 in July.
The sea catfish is very responsive to seasonal temperature changes and is most abundant in the summer months when temperatures are highest
(Figure 30). O ffshore movement is in itia te d w ith the f i r s t cool temperatures in September and can be seen clearly in Figure 30.
Although taken in salinities from 4-32 °/oo and temperatures from 15-35°C, sea c a tf is h were most common in medium to high s a l i n i ties and at temperatures from 28-30°C. They were taken at all stations but abundance was greatest at station 3 where salinities averaged Figure 30. Seasonal biomass and number of Arius felis taken with combined gear at all stations, March 1971 - June 1972. 1642
Number/ha.
Biomass kg/ha. — 1.2 E o a . E <0
O o
X 4> <0u wu V CL. V Q. E w 00 o
E Z o
3/264/16 5/7 5/25 6/14 7/7 7/28 8/28 9/2110/14 11/4 11/23 12/16 1/12 2/2 2/24 3/14 4/4 4/29 5/17 6/7 6/28
1971 - 1972-
Date >0 93
19 °/oo. Forty-two percent of all sea catfish taken were caught at th is s ta tio n . Numbers decreased ra p id ly a t s a l i n i t i e s below 15 °/oo and only 13 sea catfish were taken at station 6.
Sea catfish ranging from 12 to 452 mm were taken. A large male was taken at station 5 in July bearing young sea catfish still in the yolk sac stage. The smallest of these larvae was 12 mm. Both the smallest and largest sea catfish were taken at station 5. No relation between size and salinity was evident.
Although a common estuarine dependent fish, the sea catfish is generally regarded as a "trash" fish and has little sport fishery value. Commonly called the "hardhead," it is one of those fish gen erally classified by fishermen as "useless." It serves, however, an important role as a scavenger in the estuarine ecosystem. Dunham
(1972) reported that the sea catfish comprised 3.4% of the total weight of the industrial bottomfish landings in Louisiana.
Biomass, Abundance and Distribution of Less Abundant and Rare Species
The other 95 species taken in this study comprised 17% of the total number and 59% of the total weight of fish caught. Seasonal biomass and abundaftce of 27 species is presented in Table 7. At least
75 specimens of each of these species were taken. For fishes taken fewer than 75 times, distribution data became spotty and it was diffi cult to draw any conclusions concerning seasonal trends. Twenty-two species were taken only once and two of these are new records for
Louisiana. Erotelis smaragdus civitatum and Gunterichthys lonRipenis were previously unrecorded from Louisiana (Wagner, 1971). Table 8
Total Number and Biomass, Length Range, Maximum and Minimum Salinities and Temperatures, Location and Method of Capture of All Species Taken in the Caminada Bay Area March 1971 - June 1972
T otal T o tal Mean Length Salinity Temperature 3 b Species Number Weight Bioma! Range Range Range S ta tio n Gear (8) g/m (mm) °/oo °C
Anchoa mit chi H i 52633 34201.4 .29 16-92 .2-34 12-35 0-6 T,S Brevoortia patronus 14782 23012.9 .15 22-261 .2-31 12-35 0-6 T,S,TN Leiostomus xanthurus 5786 20404.7 .28 18-228 1.5-31 12-35 0-6 T,S,TN Micropogon undulatus 5300 22949.2 .21 11-241 .2-34 12-35 0-6 T,S,TN Membras m artinica 4514 20814.9 1.07 40-111 6-32 15-31 0 , 1,3,5 S Arius felis 2169 52539.2 .63 12-452 4-32 15-35 0-6 T,S,TN Chloroscombrus chrysurus 1538 4650.3 .53 20-89 18-31 27-31 0-3 T,S Anchoa hepsetus 1528 2382.7 .11 37-108 7-31 16-31 0.6 T,S Bagre marinus 1011 8166.6 .62 69-186 1-28 25-31 0 , 2 ,3 ,5 ,6 T,S Bairdiella chrysura 899 31206.9 .88 31-189 1-28 12.5-31 0-6 T,S Menidia bervllina 836 2374.1 .10 42-102 3.5-32 12.5-35 0-3,5 S Fundulus grandis 545 1428.2 .47 47-163 15-26 18-35 1,2 S Cvnoscion arenarius 493 * 1779.6 .04 25-164 1-28 15-35 1-6 T,S Opisthonema oglinum 372 920.9 .05 61-123 20-31 26-31 0 ,1,5 T,S Sphoeroides parvus 331 1335.9 .03 17-101 6-32 15-31 0-5 T,S Chaetodrpterus faber 311 3903.5 .14 12-98 4-34 16-31 0-5 T,S,TN Alosa chrvsochloris 276 1053.5 .09 39-366 4-31 12-31 0 , 1,3,5 T,S Citharichthys spilopterus 248 759.5 .02 19-119 4-32 14-35 0-6 T,S Fundulus similis 202 734.0 .19 55-117 15-26 18-31 0-3 S Mugil cephalus 181 18320.9 .38 22-350 1.5-32 15-35 0-6 T,S,TN Trichiurus lepturus 158 2205.1 .08 100-485 4-28 16-29 1-6 T,S Symphurus plagiusa 150 919.3 .03 19-131 4-28 12-35 1-5 T,S Gobionellus boleosoma 106 54.5 .004 23-62 8-26 12-25 1 , 2 ,3 ,5 ,6 T,S
vO ■p« Table 8 (continued) Total T otal Mean Length Salinity Temperature Species Number Weight Biomass Range Range Range Station3 G e a r ^ (g) g/m2 (mm) °/oo °C
Menticirrhus americanus 104 3141.8 .17 40-300 8-32 15-35 0-4 T,S,TN Anchoa lyolepis 103 132.1 .09 47-85 25-32 28-31 0 S Larimus fasciatus 84 171.2 .03 28-115 25-32 28-31 0 S Cvnoscion nebulosus 76 8357.0 .24 64-434 .2-32 12.5-31 0-6 T,S,TN Laeodon rhomboides 73 1801.1 .09 31-175 4-28 17-35 0-5 T,S,TN Stronevlura marina 64 1231.6 .16 165-420 10.5-31 23-31 0-3,5 S PeDrilus alepidotus 60 1047.5 .11 25-242 8-31 21-31 0 ,1 ,3 - T,S,TN Fundulus confluentus 57 22.8 .10 23-40 19.5 24 2 Antimycin Faralichthys lethostigma 50 4600.7 .26 20-400 1.5-26 14-35 0-3,5 6 T,S,TN Achirus lineatus 44 130.1 .01 26-67 2-22 16-30 1 -3 ,5 ,6 T,S Poecilia latipinna 41 10.1 .05 21-31 19.5 24 2 Antimycin Etropus crossotus 41 228.6 .02 34-125 12-24 15-29.5 1-4 T,S Synodus foetens 39 602.3 .04 32-251 9-26 16-35 0-4 T,S Trachinotus carolinus 30 199.3 .04 27-129 20-32 22.5-31 0,1 S Archosargus probatocephalus 25 18464.3 1.11 27-528 1.5-31 18-31 1-6 T,S,TN Prionotus tribulus 24 113.4 .009 18-173 10-26 15-29 1-5 T,S,TN Microgobius thalassinus 23 24.3 .002 21-46 12-23 17-28.5 1,2,3 T,S Polydactylus octonemus 22 516.5 .07 77-168 15-32 26-31 0 , 2 ,3,5 T,S Caranx latus 22 15.9 .002 21-45 18-34 21.5-31 0,1,3 T,S Caranx hippos 20 653.8 .07 41-234 4-28 24-30 0 , 2-6 T,S,TN Oligoplites saurus 20 108.9 .05 25-132 15-25 23-28 0 S Peprilus burti 19 7.5 .002 17-50 8-22 12-21.5 3 T,S Pogonias cromis 17 647.3 .30 184-283 1.5-15.5 18.8-21 6 T,TN Sciaenops ocellata 15 4080.7 .80 56-572 4-30 18-29 0,2-5 S ,TN Scomberomorus maculatus 14 66.7 .02 31-100 10.5-31 24-31 0 ,1 ,5 S Dorosoma petenense 14 213.0 .03 113-165 15-22 17-30 2,5 S ,TN Gobionellus hastatus 13 144.6 .02 50-194 15-28 18-35 1,2 T,S Elops saurus 13 1610.8 .10 146-330 4-25 21-30 0 ,4 ,5 ,6 S ,TN Gobi'osoma bosci 12 7.1 .0009 22-47 . 2-22 13.5-26 2-6 T,S Mugil curema 11 117.1 .05 72-119 15-28 27-30 1,3,5 S Cvorinodon variegatus 10 8.6 .01 31-39 15 18 2 S
SCU1 Table 8 (continued) T otal T otal Mean Species Number Weight Biomass Range Range Range S ta tio n 3 Gear^ o , (g) g/m2 (mm) /oo °C
Dasyatis sabina 8 11842.7 .24 415-1000 10-26 17-35 2,3,5 T,S,TN Eucinostomus argenteus 7 27.7 .009 36-113 16-24 16-29.5 1,2 T,S Paralichthys albigutta 7 ---- 40-61 8-15.5 18.8 5,6 T Hirundichthys rondeleti 6 0.9 — 23-46 23 21 0 Dip net Opsanus beta 6 116.5 .04 84-141 15.5-26 16-35 2,3,6 T,S Sardinella anchovia 6 2.0 .001 32-69 25-32 28-31 0 S Dorosoma cepedianum 5 653.7 .05 135-345 4-20 21-33 4 ,5 ,6 S,TN Ophichthus gomesi 4 100.1 .03 251-353 12-26 28-35 2.4,5 T Hyporhampus u n ifasciatu s 4 40.0 .05 142-164 28 28 0 S Pomatomus s a lt a tr ix 4 6.7 .004 42-67 20 21.5-24 0,3 S Vomer setap in n is 4 13.2 .005 48-69 24-28 28-29.5 0,3 T,S Gobionellus shufeldti 4 2.6 .002 35-46 10-12 19-22 2,3 T Lepisosteus spatula 3 20550.0 .78 789-1170 4-13.5 14-20 2,4 6 T,TN Gobiesox strumosus 3 5.8 .002 38-56 4-32 27-31 0 , 1.6 S ,TN LeDODhidium g ra e lls i 3 2.2 .003 82-112 10-16 19-23 3,4 T Lucania parva 3 2.1 .003 45-48 -- 2 S Centropristis philadelphica 3 6.8 .009 50-65 26 26 1 S Menticirrhus littoralis 3 3.3 .004 30-60 --— 0 S Prionotus roseus 3 2.0 .002 35-45 19-28 18-22 1 T Adenia xenica 2 2.1 .003 30-32 15 18 2 S Syngnathus louisianae 2 6.3 .004 143-234 18-20 24-27.8 1,2 T Syngnathus scovelli 2 2.3 .002 116 9 25 4 T Lutjanus synagris 2 1.5 .002 32-41 26 31 1 S Astroscopus y-graecum 2 67.0 .04 88-146 25 24-28 0,1 S Rhizoprionodon terraenovae 1 149.2 .20 330 25 28 0 S Carcharhinus leucas 1 3100.0 2.34 840 18 22 4 TN Lepisosteus platystomus 1 2000.0 1.51 754 4 30 6 TN Ictalurus catus 1 620.7 .47 380 3 22.5 6 TN Urophycis floridanus 1 6.1 .007 93 10 19 3 T
ov C Table 8 (continued) Total Total Mean Length Salinity Temperature h Species Number Weight Biomass Range Range Range S ta tio n Gear (g) g/m (mm) °/oo °C
Gunterichthys longipenis 1 .44 .0005 43 27 24 2 T Selene vomer 1 5.0 .006 66 13 25 3 T Trachinotus falcatus 1 3.4 56 — -- 2 T Coryphaena equisetus 1 .9 58 23 21 0 Dip net Lutjanus griseus 1 126.3 .10 212 18 28 4 TN Rachycentron canadum 1 1021.5 475 -- --- 0 Hook, lin e Orthopristis chrysoptera 1 278.7 250 - ~ - — 0 Hook, lin e Sphyraena guachancho 1 19.3 .02 158 22 29 3 T Hypsoblennius ionthus 1 .22 24 • “ ~ — Sea Grant Hand Camp Captur< Eleotris pisonis 1 25.1 .03 129 19 18 1 T Erotelis smaragdus civitatum 1 8.9 .01 127 19 18 1 T Gobioides broussonneti 1 8.0 .01 144 21 27 2 T Gobiosoma robustum 1 .5 .003 27 17 25 2 Antimyc: Evorthodus lvricus 1 .4 52 ** • Bayou 10’ Thunder seine Prionotus rubio 1 .5 .0006 37 18 22 4 T Ancvlopsetta quadrocellata 1 85.9 172 — Lake 32' Palourde Trawl Trinectes maculatus 1 9.0 .001 73 20 33 6 T
T otal 97223 376119.7 .44 c Lepisosteus oculatus Conerina flava Harengula pensacolae Porichthys porosissimus Histrio histrip Gambusia affinis Syngnathus floridae Table 8 (continued)
Lobotes surinamensis Eucinostomus gula Dormitator maculatus Microgobius gulosus Scomberamdrus cavalla Aluterus schoepfi
^ o t all specimens collected in this study were from the regular sampling stations. Those from other locations in the Caminada Bay area are listed specifically. bThe three primary types of gear used are abbreviated as follows: T - 16' trawl; S - 75' seine, TN - 300' trammel net. Other methods of collecting were used qualitatively and are noted. cThis and the following 12 species were not taken in this study but are known to occur in the area according to previous studies. 99
Of the top 27 species, biomass was highest for 6 species in the spring, 13 in the summer, 3 in the fall and 5 in the winter. All species with highest biomass in the fall and winter were either estuarine or estuarine dependent fishes. The primarily marine species were most common in the bay in the summer. A dults of these marine fishes are seldom found inshore, but juveniles were taken occasionally in the lower bay. Twenty-one species of this category were taken and are listed as follows: Trachinotus carolinus, T. falcatus, Oligoplites saurus, Selene vomer, Scomberomorus maculatus, Hirundichthys rondeleti,
Sardine11a anchovia, Opisthonema oglinum, Hyporhampus unifasciatus,
Pomatomus s a l t a t r i x , C e n tro p ris tis p h ila d e lp h ic a , M enticirrhus litto ralis, Larimus fasciatus, Orthopristis chrysoptera, Rachycentron canadum, Lut.janus synagris, Coryphaena equisetus, Astroscopus y-graecum,
Gunterichthys longipenis, Sphyraena guachancho, and Anchoa lyolepis.
A brief discussion of the species taken more than 75 times follows, arranged in order of decreasing abundance.
Membras martinica - There were 4,514 rough silversides taken from
n 40-111 mm with a mean biomass of 1.07 g/m . They were most abundant from July to November w ith peak lev els of biomass occurring in Ju ly .
None were taken from December to March. Greatest abundance was at the more saline stations although a specimen was taken on one occasion in
6 °/oo. Ripe specimens were noted in early April.
Chloroscotnbrus chrysurus - A total of 1,538 Atlantic bumpers were taken from 20-89 mm having a mean biomass of .53 g/m . They were taken only in the summer months and at the lower 4 stations at salinities ranging from 18 to 31 °/oo. Biomass was highest in August. 100
Anchoa hepsetus - There were 1,528 striped anchovies taken ranging 9 from 37 to 180 mm having a mean biomass of .11 g/m . Abundance and biomass were greatest In July and specimens were taken only from May to November. There were specimens caught at all stations but greatest concentrations occurred at the lower 3 stations In higher salinities.
Bagre marlnus - There were 1,011 gafftopsall catfish caught ranging from 69-186 mm having a mean biomass of .62 g/m . Abundance and bio mass were greatest in June with specimens taken from June to October.
After October, offshore movement occurred and none were found In inshore waters in the winter and spring. Gafftops were taken in salinities from 1 to 28 °/oo and at all stations except station 1. Abundance was highest however at station 3 where salinities averaged 19 °/oo. Spawn ing occurs in the summer.
Bairdiella chrysura - There were 899 silver perch caught from 31- 2 189 mm having a mean biomass of .88 g/m . Although taken in every month, silver perch were most abundant in February at station 0. Biomass was also highest at this time. The silver perch ranked third in terms of weight with 8.3% of the total biomass. Silver perch were caught at all stations and at salinities from 1 to 28 °/oo. The smallest specimens were taken during May, June, and July indicating an April to June spawning period.
Menidia beryllina - The tidewater silverside is a resident estuarine fish and was taken during all months of this study. A total of 836 were caught ranging from 42-102 mm with a mean biomass of .10 g/m^. Abundance and biomass was greatest in April and lowest in
December. This fish frequents the shallow vegetated marsh shoreline 101
and was never found far from shore in deeper water. It was taken at
all stations where the seine was used, more specifically stations 0 ,
1, 2, 3, and 5. The seine was the only gear effective for it.
Specimens were taken in salinities from 3.5 to 32 °/oo. The smallest
specimens were taken from late April to early June indicating a late
spring spawning period.
Fundulus grandis - The Gulf killifish is also a resident estuarine
species occurring most commonly in shallow marsh ponds and tidal creeks.
A total of 545 were taken, ranging from 47 to 163 mm with a mean biomass
of .47 g/m^. The majority of the specimens (520) were taken in January
at station 2 with the bag seine. Although this fish is very abundant
in the marsh pond habitat it was not common in the trawl or seine
catches except during the above mentioned sample. Apparently, cold
water temperatures had driven these fish out of the shallow ponds into
the deeper and slightly warmer nearshore area where they were suscep-
table to seine capture. I do not feel that these fish are actually
most abundant in January as my data indicate. This January peak was
probably due to a combination of meteorological conditions and sampling bias. Simpson and Gunter (1956) report spawning in October which is
probably when abundance is greatest. Specimens were taken sporadically
in March, May, and June. In an Antimycin study of October 1971, an
additional 118 Gulf killifish ranging from 28 to 73 mm were collected
in two shallow marsh ponds. Other than that, specimens were taken only
at stations 1 and 2 and in salinities from 15 to 26 °/oo.
Cynoscion arenarius - There were 493 sand seatrout taken ranging 2 in size from 25 to 164 mm having a mean biomass of .04 g/m . This . 102 species was most abundant in the spring and summer months, moving off shore to overwinter after colder weather in November. Specimens were taken from early A p ril to la te November w ith g re a te s t abundance in
May. Smallest specimens were taken in July and September indicating summer spawning. Biomass was highest in May and June. Individuals were caught at stations 1-6 and in salinities from 1 to 28 °/oo.
Opisthonema oglinum - A total of 372 Atlantic thread herring were taken ranging from 61 to 123 mm with a mean biomass of .05 g/m .
Nearly all the specimens were caught in July when 367 were taken on the beach at station 0 with the bag seine. Three fish were caught in
May at station 5 and 1 in August at station 0. This fish is apparently primarily an offshore species moving inshore only in the summer months.
None were taken from September to April. Specimens were taken in a salinity range of 20 to 31 °/oo.
Sphoeroides parvus - A total of 331 least puffers were taken ranging from 17 to 101 mm with a mean biomass of .03 g/m . A fairly uniform abundance occurred from June to November with minor variations in numbers caught. Abundance and biomass were slightly higher in
October and November a f te r which numbers dropped ra p id ly as fis h moved offshore. Small specimens (less than 25 mm) were taken from April to
July indicating a spring to early summer spawning period. Individuals were caught at stations 0-5 in salinities from 6 to 32 °/oo.
Chaetodipterus faber - There were 311 Atlantic spadefish caught, 2 ranging from 12 to 98 mm with a mean biomass of .14 g/m . This fish was most abundant in the bay in the summer and early fall and was completely absent from December to early June. Biomass was highest in 103
October prior to offshore movement. I took only juveniles of this species In the bay. Adults rarely move Inshore but are common off shore around the oil platforms (personal observation). The smallest specimens were taken in June and July indicating a late spring spawn ing period. They were collected at stations 0-5 and salinities from
4 to 34 °/oo but were more abundant at the higher salinities in the
lower bay.
Alosa chrysochloris - There were 276 skipjack herring taken rang
ing from 39 to 366 mm with a mean biomass of .09 g/m^. This fish is one of the few semi-anadromous species taken in the Gulf region. Skipjack herring migrate up large freshwater rivers in the spring to spawn and juveniles return to estuarine waters to mature. Abundance and biomass was greatest in July when 242 juveniles (41 to 71 mm) were taken at
station 0. The largest specimen. (366 mm) was taken in February at
station 0. This species was captured at stations 0, 1, 3, and 5 and
in salinities from 4 to 31 °/oo.
Citharichthys spilopterus - There were 248 bay whiffs taken ranging from 19 to 119 mm with a mean biomass of .02 g/m^. This fish was widely distributed throughout the study area and was taken during every month of the year. Abundance and biomass was greatest in June.
It was taken at all stations and in salinities from 4 to 32 °/oo. The
sm allest specimens were taken from November to January in d ic a tin g the
species is probably a fall spawner.
Fundulus similis - There were 202 longnose killifish caught ranging
from 55 to 117 mm with a mean biomass of .19 g/m^. This is an estuarine
species found in shallows along marshy shorelines usually in high
salinities. I took specimens at stations 0-3 and In salinities from 104
15 to 26 °/oo. It seems to prefer a sandy substrate and Is common on shallow protected sandy beaches. As was the case for Fundulus grandIs. most of the specimens were taken in January at station 2 when low water temperatures had driven the fish to deeper waters. Simpson and Gunter (1956) report July spawning for longnose killifish in
Texas. Due to the nature of this fish's preferred habitat, its true abundance was not evident from my sampling.
Mug11 cephalus - A total of 181 striped mullet were taken ranging from 22 to 350 mm w ith a mean biomass of .38 g/m^. This species is among the most abundant fishes on the shallow bay flats but my data do not represent its true abundance because of the striped mullet's adeptness in avoiding capture. This fish became more susceptible to capture during the colder months when it was more lethargic and was concentrated in deeper bayous and channels. Abundance was greatest in
June and biomass was greatest in January although the fish was taken every month except February. Striped mullet were captured at all
stations and in salinities from 1.5 to 32 °/oo. Arnold and Thompson
(1958) rep o rted November spawning of s trip e d m ullet s lig h tly offshore
in the Gulf of Mexico. I collected postlarval mullet at a length of
22 mm on the Gulf beach in late November.
Trichlurus lepturus - There were 158 Atlantic culassfish taken ranging from 100 to 485 mm with a mean biomass of .08 g/m^. This fish was p resen t inshore from February to November w ith peak abundance and biomass in April. It was taken at stations 1-6 and in salinities from
4 to 28 °/oo. Gunter (1938) reported a summer peak of Atlantic cut
lass fish in Barataria Bay. 105
Symphurus plagiusa - There were 150 blackcheek tonguefish taken ranging from 19 to 131 mm with a mean biomass of .03 g/m . Blackcheek tongueflsh were caught every month of the sampling period but Its abundance and biomass was highest In November. The smallest specimen was taken In November so It Is apparently a fall spawner. Individuals were caught at stations 1-5 and in salinities from 4 to 28 °/oo.
Goblonellus boleosoma - There were 106 darter gobies caught ranging from 23 to 62 mm with a mean biomass of .004 g/m . This small estuarine fish was most common over shallow muddy bottoms at salinities from 8 to
26 °/oo. Darter bogies were taken at stations 1-6. Peak abundance and biomass occurred in January. Oddly, this fish was taken only from
November to early May and was not collected in the warmer summer months.
The darter goby was the most abundant species of the family Gobiidae which was represented in this study by nine species, all of which are e stuarine.
Menticirrhus americanus - There were 104 southern kingfish taken 2 ranging from 40 to 300 mm with a mean biomass of .17 g/m . Specimens were caught sporadically through the sampling period with peak abundance and biomass in May. Southern kingfish were collected at stations 0-4 and in salinities from 8 to 32 °/oo. The smallest specimens were taken in May and July so it is apparently a spring spawner.
Anchoa lyolepis - There were 103 dusky anchovies taken ranging 2 from 47 to 85 mm with a mean biomass of .09 g/m . This fish is found primarily offshore but was taken on the sampling trips in May and June on the Gulf beach. No other specimens during the entire study were collected. Specimens were taken at salinities from 25 to 32 °/oo. 106
Larimus fasclatus - There were 84 banded drum taken ranging from 2 28 to 115 mm with a mean biomass of .03 g/m . This Is also a fish found primarily offshore but It was collected on two occasions on the
Gulf beach In May and June at salinities of 25 and 32 °/oo.
Cynosclon nebulosus - There were 76 spotted seatrout taken ranging from 64 to 434 mm with a mean biomass of .24 g/m^. These fish are estuarine completing their entire life history in Inshore waters.
Abundance and biomass was greatest in April but specimens were taken throughout the year. Tabb (1966) reported spring spawning for spotted seatrout in Florida. Although spotted seatrout were taken at all stations and in a wide salinity range from 0.2 to 32 °/oo, they were most abundant in lower salinities in the upper bay.
Rare Species
Twenty-two species were taken only once during the study. They are listed at the end of Table 8. The majority of these were primarily marine fishes that were taken in the summer months in the lower bay.
Some of the rarer gobies and sleepers were collected in the fall and one species, Urophyeis floridanus, the southern hake, was collected only in the winter. Three species of freshwater fishes were taken, all at stations in the upper study area. These were Lepisosteus platytomus, Lepisosteus oculatus, and Ictalurus catus. On March 15, 1972,
6 blackwing flying fish, Hirundichthys rondeleti, from 23 to 44 mm and 1 pompano dolphin, Coryphaena equlsetis. (58 mm) were taken with a dip net in Caminada Pass. These two fishes are generally associated with floating Sargassum weed far offshore but strong southerly winds had apparently driven patches of this week into Caminada Pass where the fishes were collected. Most of the other marine species collected 107 in this study were also taken only in their juvenile stages in the lower bay.
Two small benthic fishes were collected which are new records for
Louisiana. One specimen of the gold brotula, Gunterichthys longipenis, was taken on May 18, 1971, in Airplane Lake, station 2. The fish was caught in the 16 foot otter trawl over a muddy detritus bottom at a depth of 1.1 m, temperature of 24°C, and salinity of 27 °/oo. The second specimen, an emerald sleeper,. Erotelis smaragdus civitatum, was taken on November 4, 1971, a t a depth of 8 m in Caminada Pass, station
1. It was caught in the 16 foot otter trawl at a temperature of 18°C and a salinity of 19 °/oo. Both of these fishes are rare along the entire Gulf Coast. Dawson (1966, 1969, 1971) recorded three occur rences of Erotelis in Mississippi waters and Gunterichthys has been reported eight times from M ississippi Sound and twice from Kings Bay,
Forida. They are both thought to be burrowers, inhabiting upper sub s tr a te layers in mud-sand bottoms (Dawson, 1966, 1971). The b ro tu lid s are typically deep water fishes which only rarely move inshore into estuaries. The sleepers are a small family of estuarine fishes in habiting muddy ponds and bayous in brackish marshes. Both of these fishes were collected during adverse environmental conditions. Rapid changes in salinity, rapid temperature reduction r suiting from passage of cold fronts, or distrubances of the bottom created by dredging or trawling apparently alter the behavior of these secretive fishes, driving them from their burrows and making them more susceptible to capture. All known specimens of Gunterichthys were taken during or immediately after a period of unusual climatic conditions (Dawson, 1966). 108
My specimen was caught after Intensive repeated trawling over a small area during a mark-recapture experiment in May 1971. The specimen of
Erotelis was taken during the passage of the first strong cold front of the year. Water temperature was dropping rapidly, accompanied by rapidly falling tides and 25-30 mph northerly winds.
Trophic Level Biomass
I felt it would be of value to classify all species taken in this study so that the biomass of each trophic level could be estimated.
Grouping into trophic levels was done on the basis of food studies of estuarine fishes. Food studies have proven useful in revealing ecological relationships among various organisms in the estuarine food web. Earlier workers, notably Darnell (1958, 1961) and Odum (1971), have used this technique to determine trophic structure and pathways of energy flow. On the basis of these studies and some stomach anal ysis of my own, all species were classified as either herbivores, omnivores, primary, middle, or top carnivores. Trophic levels were » defined as follows.
Herbivores - fishes feeding primarily on vegetable matter, phyto plankton, or organic detritus.
Omnivores - fishes showing no particular preference for plant or animal material, one or the other predominating depending on avail ability in a particular habitat.
Primary carnivores - fishes feeding mostly on zooplankton and microbenthic animals hut occasionally on plant matter and organic d e tr itu s .
Mid carnivores - fishes feeding on both microbenthic and macro- 109
bcnthlc animals (such as molluscs, penaeid shrimp, small crabs), small
fishes of lower trophic levels, and organic detritus.
Top carnivores - Fishes feeding primarily on Gulf menhaden, bay
anchovy, tidewater silverside, and juvenile Atlantic croakers and the
larger invertebrates such as penaeid shrimp and blue crabs. The larval
and juvenile stages of these fishes may function as mid carnivores as
pointed out by Odum (1971). The results of this classification are in
Table 9 and a listing of trophic level by species is in Table 10. No
omnivorous fish were taken.
Table 9
Mean Standing Crop Biomass of Fishes of Each Trophic Level
Mean Biomass % T otal Num. % Tot, g/m^ wet wt. Biomass Species Num. S;
Herbivores .78 4.7 9 9.0
Primary Carnivores .57 3.5 5 5.0
Mid Carnivores 7.99 48.6 62 62.0
Top Carnivores 7.03 42.8 24 24.0
Total 16.4 100
n The mean standing crop biomass is the average biomass in grams/meter^
taken for each trophic level throughout the year. It may vary up or down depending on the season of the year and the seasonal abundance
of the species in each level.
It is evident that the majority of fishes taken in this study were mid carnivores and that they comprised nearly 50% of the total fish biomass. Gear bias may have had some effect on the biomass attributed
to each level. It has already been mentioned that the sampling methods used probably underestimated the abundance of the Gulf menhaden and the striped mullet, both of which are herbivores. Traditionally, higher biomass has been found in organisms at lower trophic levels
(Odum, 1959). However, the data from my analysis indicated that most of the biomass of fishes is found among the mid and top carnivores.
Perhaps the turnover rates of herbivores and primary carnivores are higher than for mid and top carnivores. Although a lower standing crop biomass is present, the production at the lower trophic levels would be higher. Another reason the higher trophic levels apparently had a higher biomass is the obvious fact that larger fishes naturally weigh more than smaller fishes, although there are fewer of them.
The above scheme represents biomass of only the fish population. If the biomass of all organisms of each trophic level in the estuarine ecosystem were compiled, it is probable that the herbivores and pri mary carnivores would then be greatest in biomass.
Seasonal Movements and Migrations
One of the most significant characteristics of Caminada Bay fishes is the fa c t th a t most e x h ib it almost co n tin u al movement from e ith e r one section of the bay to another or between the bay and offshore waters of the Gulf. There is virtually no period in the year when some movement is not occurring. M igration u su ally involves immigra tion from the Gulf to the bay or emigration from the bay to the Gulf for spawning, feeding, or overwintering. Other smaller movements occur which are not true migrations. They may be local movements of physio
logical adjustment in response to changes in temperature or salinity.
The importance of temperature as a factor affecting seasonal movements I l l has already been d iscussed. An example of seasonal movement confined w ith in the estu ary i s the movement of fish e s from shallow sh o relin e
flats to deeper waters of bayous and bays associated with decreases
in temperature. Freshets caused by heavy rainfall may rapidly de crease the salinity of the bay inducing movement to more saline waters.
Five migrations occur among the fishes in the Caminada Bay area.
Arranged chronologically through the year these are:
1) an early spring inshore feeding migration of postlarvalestua rine dependent species utilizing the area as a nursery ground
2) a spring spawning migration through the bay into freshwater rivers and bayous by certain semi-anadromous species of the family
Clupeidae
3) a gradual early summer offshore spawning migration by maturing estuarine dependent sub-adult fishes
4) a mid summer to early fall inshore migration by juveniles and occasional transient adults of primarily marine species
5) a fall offshore overwintering migration of all fishes except resident species and young of the year recruits of estuarine dependent
species. There is a counter movement to this migration by the southern hake, Urophycis floridanus, which is found inshore only during the winter and early spring.
Early Spring Inshore Feeding Migration
This migration reaches a peak in March when great numbers of post-
larval fishes enter the lower estuary after being spawned offshore.
Dunham (1972) found peak concentrations of larval fish occurred in
Caminada Pass in March. Upon entering the bays, most of the fish have •>
1 1 2 grown to postlarvae and are capable of some locomotion. They are transported by saline bottom current (Haven, 1957) and rising tides to the brackish marshes of the upper bay. Most of the commercially important species move into the bay in the spring. Included are striped mullet, Gulf menhaden, southern flounder, Atlantic croaker, sp o t, red drum and most of the other scia e n id s. Inshore movement of the Atlantic croaker and striped mullet actually began in November
1971 but peaked in the early spring.
Spring Spawning Migration Into Freshwater
Three semi-anadromous species were taken in this study, all of which were herrings of the family Clupeidae. These fishes move north ward through the bay in the spring and enter freshwater rivers and bayous for the purpose of spawning. Juveniles move back down to estuarine waters where they remain until maturity. The skipjack herring, Alosa chrysochloris, and threadfin shad, Dorosoma petenense, were both taken as juveniles in the lower bay in the summer. Skipjack herring were taken in salinities ranging from 4 to 31 °/oo and the threadfin shad in salinities from 15 to 22 °/oo. One adult skipjack herring (366 mm) was taken in February. Five Gizzard shad, Dorosoma cepedianum, were taken in salinities from 4 to 20 °/oo in the upper bay. This species was reported to be anadromous in the York River system of Virginia (McHugh, 1967) and semi-anadromous along the northern Gulf Coast (Gunter, personal communication). Shad runs occur in the early spring in Bayou Lafourche and I have observed commercial fishermen using dip nets to capture them at a small dam near Thibodaux,
L ouisiana. 113
Early Summer Offshore Spawning Migration
An offshore migration of certain estuarine dependent species begins in Hay after they reach a March and April peak in numerical abundance. Atlantic croaker, spot and Gulf menhaden follow this pattern, which is reflected in the sharp drop in numerical abundance in e a rly summer. This gradual movement continues a l l summer as growing sub-adult fishes approach spawning condition and move off shore. Actually, the movement of the estuarine dependent species never really stops. They move to the brackish upper estuary in early spring and gradually migrate down the bay through increasing salinity as they grbw.
Mid Summer-Early Fall Inshore Migration
Most of the primarily marine species (Table 10) migrate into the lower bay from about July to September. Juveniles and occasional transient adults of this group were taken at that time. The greatest number of species are present in the late summer period when a com bination of estuarine, estuarine-dependent and marine fishes are found in the bay.
Fall Offshore Overwintering Migration
The most noticeable migration was the rapid offshore overwintering migration associated with decreasing water temperatures. This migration began in November'1971 and was associated with the passage of a cold front. On November 4, 1971, 22 species were collected at station 1 in Caminada Pass. Strong northerly winds were producing rapidly falling tides and water temperatures and it seemed evident the fish were trying to escape the bay for warmer waters offshore. Nikolsky 114
(1963) states that such overwintering migrations are triggered by natural stimuli such as changes in temperature after the fishes have undergone advance physiological preparation for the migration.
Numerical abundance and biomass after this migration were the lowest of the year and the only fishes found inshore were resident species and a few recruits of estuarine dependent species which had been recently spawned and had moved inshore.
Categorization of Fishes
I have found five categories of fishes in the Caminada Bay area based on their estuarine dependency (Table 10). This classification is modeled after that of McHugh (1967). Virtually all of the 100 species collected in this study show some degree of reliance on the estuary. The categories include 3 species of freshwater fishes that occassionally enter brackish waters, 3 species of semi-anadromous fishes which migrate up through estuaries to freshwater spawning grounds, 32 species of estuarine fishes that complete their entire life cycle in estuarine waters, 40 species of estuarine dependent fishes which spawn in the Gulf and migrate as postlarvae into the estuary where they reside through their juvenile phases, and 35 species of primarily marine fishes which are found mainly offshore but occur as occasional transients in the lower bay.
The 3 species of freshwater fishes were Lepisosteus oculatus,
L. platystomus and Ictalurus catus. All were taken in the upper bay at station 6.
Three species of semi-anadromous fishes were taken in this study,
Alosa chrysochloris, Dorosoma cepedianum and D. petenense. I consider 115
these species as semi-anadromous because they mature in estuarine
rather than Gulf waters after spawning in freshwater (Gunter, personal
communication). True anadromous species spawn in fresh water but
spend their sub-adult stages in the sea.
The 32 species of resident or estuarine fishes include Rhizo-
prionodon terraenovae, Carcharhinus leucas, Dasyatls sabina, Lepisos
teus spatula, Anchoa m itchilli, Opsanus beta, Gobiesox strumosus,
Menidia beryllina, Syngnathus scovelli, Cynoscion nebulosus, Trinectes maculatus and all members taken of the Cyprinodontidae, Poeciliidae,
Blenniidae, Gobiidae and Eleotridae. This group of fishes spawn in shore and do not undergo extensive migrations to offshore waters.
Their movements may be limited to a rather restricted micro-habitat within the estuary. The skilletfish, Gulf toadfish, and freckled blenny are found primarily around and in oyster reefs and beds. The
tidewater silverside and the killifishes and livebearers are found most of the time along shallow vegetated marshy shorelines or within marsh ponds and tidal creeks. The spotted seatrout does occasionally move into neritic offshore waters but is essentially non-migratory.
Although movements to escape winter cold and freshets have been described for the spotted seatrout, these are chiefly short movements and probably cannot be considered true migi. '.tions (Tabb, 1966). Tabb also reports that spotted seatrout rarely leave their natal estuary and seldom move more than 30 miles.
The 40 species of estuarine dependent fishes include Mugil cephalus, Brevoortia patronus, Paralichthys lethostigma, Arius felis,
Lagodon rhomboides, most of the Sciaenidae and others listed in Table 116
10. These fishes spawn as adults in the Gulf and postlarvae move
inshore into the bay where they spend their juvenile and sub-adult
stages for period of 3 to 10 months. This group may be considered
as having a semi-catadromous life cycle. Instead of spending their
juvenile stages in freshwater as true catadromous species do, the
estuarine-dependent species mature in the estuarine waters of the bay.
Movement back offshore occurs as they near m atu rity .
I have classified 35 species as primarily marine species. In
cluded in th is group are Pomatomus s a l t a t r i x , Scomberomorus m aculatus,
Selene vomer and others listed in Table 10. These fishes spawn off
shore and complete their entire life cycles offshore. Juvenile
fishes of this group occasionally move inshore into the lower bay
but may not be required to do so for survival. Adults may move into
the lower bay as irre g u la r tra n s ie n ts in the la te summer.
Seasonal and Areal Species Composition
In terms of numerical abundance, the dominant families taken in
this study were (in order of decreasing abundance) Gngraulidae (55.8%),
Clupeidae (15.9%), Sciaenidae (13.1%), Atherinidae (5.5%), Ariidae
(3.3%), and Carangidae (1.7%). The families with the highest number
of species represented were the Sciaenidae (10), Gobiidae (9),
Car'ingidae (8), Clupeidae (7) , Cyprinodontidae (6), and Bothidae (5) .
Certain species had a very distinct seasonality, being found in
the bay for only short periods of the year while others were found
throughout the year. There were 13 species taken only in the spring,
19 species taken only in the summer, 4 species taken only in the f a l l ,
3 species taken only in the winter and 11 species taken throughout the 117
Table 10
Taxonomic Check List, Trophic Level, and Category of Fishes
of the Caminada Bay System
Trophic Level Category
Class Chondrichthyes . Order Squaliformes Carcharhinidae-Requiem Sharks Rhizoprionodon terraenovae-Atlantic Sharpnose Shark T E Carcharhinus leucas-Bull Shark T E
Order Rajiformes Dasyatidae-Stingrays Dasyatis sabina-Atlantic Stingray M
Class Osteichthyes Order Semionotiformes Lepisosteidae-Gars Lepisosteus oculatus-Spotted Gar T F Lepisosteus platystomus-Shortnose Gar T F Lepisosteus spatula-Alligator Gar T E
Order Elopiformes Elopidae-Tarpons Elops saurus-Ladyfish M PM
Order Anguilliformes Congridae-Conger Eels Congrina flava-Yellow Conger T PM
Ophichthidae-Snake Eels Ophichthus gomesi-Shrimp Eel T PM
Order Clupeiformes Clupe idae-HerrIngs Alosa chrysochloris-Skipjack Herring H SA B revoortia patronus-Gulf Menhaden H Ed Dorosoma cepedianum-Gizzard Shad P SA Dorosoma petenense-Threadfin Shad P SA Harengula pensacolae-Scaled Sardine H PM Opisthonema ogllnum-Atlantic Thread H erring H PM Sardinella anchovia-Spanish Sardine H PM 118
Table 10 (continued)
Trophic Level Category
Order Clupeiformes (Con't) Engraulidae-Anchovies Anchoa h ep setu s-S trip ed Anchovy P PM Anchoa lyolepis-Dusky Anchovy P PM Anchoa m i t c h i l l i -Bay Anchovy P E
Order Myctophiformes Synodontidae-Lizardfishes Synodus foetens-Inshore Lizardfish T Ed
Order Siluriformes Ariidae-Sea Catfishes Bagre marinufr-Gafftopsail Catfish M Ed Arjus felis-Sea Catfish M Ed
Ictaluridae-Freshwater Catfishes Ictalurus catus-White Catfish M F
Order Batrachoidiformes Batrachoididae-Toadfishes Opsanus beta-Gulf Toadfish M E Porichthys poros is s imus-Atlant ic Midshipman M PM
Order Gobiesociformes Gobiesocidae-Clingfishes Gobiesox strumosus-Skilletfish M E
Order Lophiiformes Antennar i idae-Fr ogf ishes Histrio histrio-Sargassumfish M PM
Order Gadiformes Gadldae-Codfishes Urophycis floridanus-Southern Hake M PM
Ophidiidae-Cusk-Eels + Brotulas Lepophidium graellsi-Blackedge Cusk-eel M PM Gunterichthys longipenis-Gold Brotula M PM
Order Atheriniformes Exocoetidae-Halfbeaks and Flyingfishes Hyporhampus unifasciatus-Halfbeak T PM Hirundichthys rondeleti-Blackwing Flyingfish M PM 119 Table 10 (continued)
Trophic Level Category
Order Atheriniformes (Con't) Belonidae-Needlefishes Strongylura marina-Atlantic Needlefish T Ed
Cyprinodontidae-Killifishes Adenia scenica-Diamond Killifish H E Cyprinodon variegatus-Sheepshead Minnow H E Fundulus confluentus-Marsh Killifish M E Fundulus grandis-Gulf Killifish M E Fundulus simi 1is-Longnose Killifish M E Lucania parva-Rainwater Killifish M E
Poeciliidae-Livebearers Gambusia affinis-Mosquitofish P E Poecilia latipinna-Sailfin Molly H E
Ather inidae-S ilver s ide s Membras m a rtin ic a -Rough S ilv e rsid e M PM Menidia beryllina-Tidewater Silverside M E
Order Gasterosteiformes Syngnathidae-Pipefishes + Seahorses Syngnathus floridae-Dusky Pipefish M Ed Syngnathus louisianae-Chain Pipefish M Ed Syngnathus scovelli-Gulf Pipefish M E
Order Perciformes Serranidae-Sea Basses Centropristis philadelphica-Rock Sea Bass M PM
Pomatomidae -Blue fishes Pomatomus s a lta tr ix -B lu e f is h T PM
C arangidae-Jacks and Pompanos Caranx hippos-Crevalle Jack T Ed Caranx latus-Horse-eye Jack M Ed Chloroscombrus chrysurus-Atlantic Bumper M Ed Oligoplites saurus-Leather jacket T PM Selene vomer-Lookdown M PM Trachinotus carolinus-Florida Pompano M IW Trachinotus falcatus-Permit M PM Vomer setapinnis-Atlantic Moonfish M Ed
Coryphaenidae-Dolphins Coryphaena e q u is e tis -Pompano Dolphin T PM 120
Table 10 (continued)
Trophic Level Category
Order Perciformes (Con't) Lutjanidae-Snappers Lut.j anus g ris e u s-Gray Snapper T Ed Lut janus synagris-Lane Snapper T PM
Lobotidae-Tripletails Lobotes surinamensls-Tripletail M PM
Gerreidae-Mojarras Eucinostomus argenteus-Spotfin Mojarra M Ed Eucinostomus gula-Silver Jenny M Ed
Rachycentridae-Cobias Rachycentron canadum-Cobia T PM
Pomadasyidae-Grunts Orthopristis chrysoptera-Pigfish M PM
Spar idae-Porgies Archosargus probatocephalus-Sheepshead M Ed Lagodon rhomboides-Pinfish M Ed
Sciaenidae-Drurns Bairdiella chrysura-Silver Perch M Ed Cynoscion arenarius-Sand Seatrout T Ed Cynoscion nebulosus-Spotted Seatrout T E Larimus fasciatus-Banded Drum M PM Leiostomus xanthurus-Spot M Ed Menticirrhus amerj1canus-Southern Kingfi'sh M Ed Menticirrhus littoralis-Gulf Kingfish M Ed Micropogon undulatus-Atlantic Croaker M Ed Pogonias cromis-Black Drum T Ed Sciaenops ocellata-Red Drum T Ed
Ephippidae-Spadefishes Chaetodipterus faber-Atlantic Spadefish M Ed
Mugilidae-Mullets Mugil cephalus-Striped Mullet H Ed Mugil curema-White Mullet H Ed
Sphyraenidae-Barracudas Sphyraena guachancho-Guaguanche T PM
Polynemidae-Threadfins Polydactylus octonemus-Atlantic Threadfin M Ed 1 2 1
Table 10 (continued)
Trophic Level Category
Order Perciformes (Con't) Uranoscopidae-Stargazers Astroscopus y-graecum-Southern Stargazer M PM
Blenniidae-Combtooth Blennies Hypsoblennius ionthas-Freckled Blenny M E
Eleotridae-Sleepers Dormitator maculatus-Fat Sleeper M E Eleotris pisonis-Spinycheek Sleeper M E Erotelis smaragdus civitatum-Emerald Sleeper M E
Gobiidae-Gobies Gobioides broussonneti -Violet Goby M E Gobionellus boleosoma-Darter Goby M E Gobionellus hastatus-Sharptai1 Goby M E Gobiosoma bosci-Naked Goby M E Gobiosoma robustum-Code Goby M E Microgobius gulosus-Clown Goby M E Microgobius thalassinus-Green Gogy M E Gobionellus shufeldti-Freshwater Goby M E Evorthodus lyricus-Lyre Goby M E
Trichiuridae-Cutlassfishes Trichiurus lepturus-Atlantic Cutlassfish T Ed
Scombridae-Mackerels and Tunas Scomberomorus cavalla-King Mackerel T PM Scomberomorus maculatus-Spanish M ackerel T PM
Stromateidae-Butter fishes Peprilus alepidotus-Harvestfish M Ed Peprilus burti-Gulf Butterfish M Ed
Triglidae-Searobins Prionotus tribulus-Bighead Searobin M Ed Prionotus roseus-Bluespotted Searobin M Ed Prionotus rubio-Blackfin Searobin M Ed 122
Table 10 (continued)
Trophic Level Category
Order Pleuronectiformes Bothidae-Lefteye Flounders Ancylopsetta quadrocellata- OceHated Flounder M FM Citharichthys spilopterus-Bay Whiff M Ed Etropus crossotus-Fringed Flounder M Ed Paralichthys albigutta-Gulf Flounder T PM Paralichthys lethostigma-Southern Flounder T Ed
Soleidae-Soles Achirus lineatus-Lined Sole M Ed Trinectes maculatus-Hogchoker M E
Cynoglo s s idae-Tonguef i she s Symphurus plagiusa-Blackcheek Tonguefish M Ed
Order Tetraodontiformes Balistidae-Triggerfishes and Filefishes Aluterus schoepfi-Orange Filefish M PM
Tetraodontidae-Puffers Sphoeroides parvus-Least Puffer M Ed
Key: Trophic Levels C ategories H - herbivore F - freshwater - complete life cycle P - primary carnivore in freshwater M - mid carnivore E - estuarine - complete life cycle T - top carnivore in estuaries SA - semi-anadromous - spawn in fresh water, mature in estuary Ed- e stu a rin e dependent - spawn at sea, young move into estuaries to mature PM- primarily marine - found mainly offshore but occur as occasional transients in lower estuary 123 year (Table 11). The remaining 50 species were taken during two or more seasons but not throughout the year. Species diversity was highest from July to October and lowest from November to February. Species diversity was highest when bay water temperatures were highest and lowest when water temperatures were lowest. From July to October the mean number ofspecies taken at each station was 10 while from Novem ber to February it was 4. The highest number of species taken on any one collection was 22 and this occurred twice, at station 3 on July
28, 1971, w ith the seine and a t s ta tio n 1 on November 4, 1971, w ith the trawl. Species diversity gradually increased through the spring after the winter minimum to a maximum in late summer and then decreased rapidly in the late fall.
Areal species composition also varied considerably; some species were taken at only one station, others at two or more and a few at all stations. There were 12 species taken at station 0 only, 5 species at station 1 only, 7 species at station 2 only, 4 species at station 3 only, 4 species at station 4 only, 0 species at station 5 only, 4 species at station 6 only and 10 species taken at all stations (Table
12). S ta tio n 2 and 3 had the h ig h est mean number of species per collection through the entire sampling period (12) while station 6 had the lowest (6). The to ta l number of species taken a t s ta tio n s 0 to 6 were 47, 48, 53, 49, 34, 40, and 30, respectively. The decrease in the number of species found northward through the bay is attributable to the decreasing salinity of the area. Gunter (1963, 1967) noted that the greatest number of species were found in high salinity and that the number of species declined in lower salinity in upper bays Table 11
Species Taken Exclusively During Each Season and All Year
Spring (MAM) Summer (JJA) F a ll (SON) W inter (DJF) A ll Year
Rhizoprionodon Opisthonema oglinum Selene vomer Lepisosteus spatula Anchoa m itchilli terraenovae Lenisosteus platv- Eleotris nisonis Urophycis floridanus Arius felis Carcharhinus leucas stomus Erotelis smarag- Gobionellus Leiostomus Ictalurus catus Ophichthus gomesi dus civitatum sh u fe ld ti xanthurus Gunterichthys Sardinella anchovia Gobiosoma Micropogon longipenis Anchoa lyolepis robustum undulatus Hirundichthys rondeleti Gobiesox strumosus Mugil cephalus Centropristis Hyporhampus Citharichthys philadelphica unifasciatus spilopterus Pomatomus s a lt a tr ix Chloroscombrus Brevoortia Coryphaena equisetus chrysurus patronus Rachycentron canadum Trachinotus falcatus Symphurus Orthopristis Vomer setapinnis plagiusa chrysoptera Lutjanus griseus Menidia beryllina Evorthodus lyricus Lutjanus synagris Bairdiella Prionotus rubio Menticirrhus chrysura Ancylopsetta littoralis Cynoscion quadrocellata Mugil curema nebulosus Sphyraena guachancho Polydactylus octonemus Gobioides broussonneti S comberomorus maculatus Trinectes maculatus Table 12
Species Taken Only At Certain Stations and At All Stations
Total Number of Species Taken in Parenthesis
Station 0 (47) Station 1 (48) Station 2 (53) Station 3 (49)
Rhizoprionodon terraenovae Centropristis philadelphica Gunter ichthys longipenis Urophycis floridanus Sardine11a anchovia Lutjanus synagris Adenia xenica Selene vomer Anchoa lyolepis Eleotris pisonis Cyprinodon var iegatus Sphyraena guachancho Hyporhampus u n ifasciatu s Erotelis smaragdus Poecilia latlpinna Peprilus burti Oligoplites saurus civitatum Trachinotus falcatus Trachinotus carolinus Prionotus roseus Gobioides broussonnBti Coryphaena equisetis Gobiosoma robustum Rechycentron canadum Orthopristis chryoptera Larimus fasciatus Menticirrhus littoralis
S ta tio n 4 (34) Station 5 (40) Station 6 (30) All Stations (100)
Carcharhinus leucas None I^pisosteus platystomus Brevoortia patronus Lut janus griseus Ictalurus catus Anchoa hepsetus Gobionellus shufeldti Pogonias cromis Anchoa m itchilli Prionotus rubio Trinectes maculatus Arius felis Bairdiella chrysura Cynoscion nebulosus Leiostomus xanthurus Micropogon undulatus Mugil cephalus Citharichthys spilopterus 126 and estuaries. Low salinities limit movement of stenohallne marine fishes into upper estuaries. Only euryhaline fishes can osmoregulate at low and high salinities.
I took the smallest specimens of most species in more saline waters at stations in the lower bay. Gunter (1957) reported that individuals of most marine species taken in fresh water were smaller than those taken in more saline water. However, he also stated that the very smallest specimens are found in waters of quite high salinity since most marine fishes spawn in or near the sea. The young, as post larvae, then move to waters of lower salinity. Accordingly, I found that for 74 of the 100 species, the smallest specimens were taken in the lower bay (stations 0-3) where salinities were higher. There is the possibility that I could have been sampling transients moving toward lower salinities. Also, I did not have a station in very low salinity water approaching that of fresh water. Gunter (1956) reported that most estuarine dependent fishes are more sensitive to salinity differ ences near the lower side of their toleration limit than the upper side.
The salinity at station 6 averaged 8 °/oo and was probably not low enough to be limiting to the distribution of some species. If I had a station in or near freshwater, a more noticeable size-salinity * gradient may have been observed due to a larger proportion of small individuals.
It is evident that there is much variation in seasonal and areal species composition. The primarily marine species were taken mostly in the summer and fall in the lower bay. Some of the estuarine species that were taken all year were essentially the same ones that were 127
taken at all stations. All species of this group were either estuarine or estuarine dependent.
Gear Selectivity
Pertinent data for comparing selectivity of the three types of
gear used in my study is presented in Table 13. It is evident that the seine captured the greatest weight, the highest mean biomass in o O g/m , the g re a te s t mean number per m , and the h ig h est number of
species of all three gear types. A total of 160.8 kg of fish were
taken with the seine compared to 130.2 kg with the trawl and 85.1 kg with the trammel net. The mean biomass available to the seine through
the e n tire sampling period was 4.51 g/m^ w hile the mean biomass was 2 2 only 1.03 g/m for the trawl and 3.58 g/m for the trammel net. The range in biomass taken by each gear was: seine, .17 to 17.07; trawl,
.37 to 2.97; trammel net, 1.49 to 5.93. The seine also captured a 9 greater mean number of fish per m (.87) in comparison to the trawl
(.58) and trammel net (.02). A total of 68 species were taken with
the seine, 60 with the trawl and 27 with the trammel net. Twenty-one
species were taken solely with the seine, 15 of which are species
associated with the surface or shallow shoreline areas. Of the 17
species taken only with the trawl, 13 are strictly bottom fishes.
Only 4 species were captured exclusively with the trammel net, all of which were taken only one time.
There were 16 species taken with all three types of gear. Those
species taken only by one gear and those taken with all gear are listed
in Table 14. The smallest fish captured during this study was an 11 mm 128
Table 13
Selectivity of the Three Types of Gear
Trawl Seine Trammel Net
Sampling Area (m2) 832.5 760.0 1327.9
Number Samples 132 47 20
Total Weight Fish (Kilogram) 130.2 160.8 85.1
Mean Biomass (g/m2) 1.03 4.51 3.58
Range in Biomass (g/m2) .37-2.97 .17-17.07 1.49-5.93
T otal Number Fish 63,863 31,092 531
Mean Number Fish/Sample 484 662 27
Mean Number Fish/m .58 .87 .02
T otal Number Species Caught 60 68 27
Number Species with Only This Gear 17 21 4
Smallest Fish Caught (mm) 11 17 56
Largest Fish Caught (mm) 1170 865 1032 Table 14
Species Taken With Only One Type of Gear and By All Gear
Trawl Seine Trammel Net A ll Gear
Ophichthus gomesi Rhizoprionodon terraenovae Carcharhinus leucas Dasyatis sabina Uronhvcis floridanus Sardinella anchovia Lepisosteus platystomus Brevoortia patronus Lepoohidium eraellsi Anchoa lyolepis Ictalurus catus Anchoa m itchilli Gunterichthvs loneipenis Hyporhampus u n ifasciatu s Lutianus griseus Arius felis Svnenathus louisianae Stronevlura marina Caranx hippos Selene vomer Adenia xenica Archosargus probatocephalus Trachinotus falcatus Cyprinodon variegatus Lagodon rhomboides Sphyraena guachancho Fundulus grandis Cynoscion nebulosus Eleotris pisonis Fundulus similis Leiostomus xanthurus Erotelis smaragdus Membras m artinica Micropogon undulatus civitatum Menidia beryllina Menticirrhus americanus Gobioides broussonneti Centrdpristis philadelphica Chaetodipterus faber Gobionellus shufeldti Pomatomus s a lt a tr ix Mugil cephalus Prionotus roseus Oligoplites saurus Prionotus tribulus Prionotus rubio Trachinotus carolinus Paralichthys lethostigma Ancyclopsetta Lutjanus synagris Peprilus alepidotus quadrocellata Larimus fasciatus Paralichthys albigutta Menticirrhus littoralis Trinectes maculatus Mugil curema Astroscopus y-graecum Scomberomorus maculatus 130
Atlantic croaker taken with the trawl and the largest a 1170 tran a lli gator gar also taken with the trawl.
Age and Growth of the A tla n tic Croaker
The life history of the Atlantic croaker in coastal estuaries is fairly well known and has been the subject of numerous workers. Be havior including movements and migration has been discussed by Bearden
(1964), Suttkus (1954) and Haven (1959). Its food habits have been studied by Roelofs (1954), Reid et al. (1956), Darnell (1958), Avault et al. (1969), Hansen (1970) and Parker (1971). Growth, spawning and seasonal and areal distribution of the Atlantic croaker have been determined by Welsh and Breder (1923), Higgins and Pearson (1927),
Pearson (1929), Hildebrand and Cable (1930), Wallace (1941), Suttkus
(1954), Haven (1957), Bearden (1964), Roithmayr (1965), Hansen (1969),
Nelson (1969), Parker (1971) and Herke (1971). The croaker growth rate from these studies at various regions along the Atlantic and Gulf coasts has been compiled in Table 15. Analysis of length-frequency distributions was the method used in all of these studies to get growth estimates. It is clear that there is a great deal of geograph ical variation in the estimated growth rate. No distinct geographical pattern was evident, however, and Parker (1971) concluded that these variations probably represented a combination of gear selectivity, inaccuracies in the techniques used to estimate growth, and year-to- year fluctuations resulting from local environmental differences in temperature and food. Averaging these estimates from Table 15 for the first three years of life, croakers grow to 149 mm in their first year,
206 mm in th e ir second,year, and 247 mm in th e ir th ird year. Table 15
Age-Length Relationship of Atlantic Croaker from Previous Studies Along the Atlantic and Gulf Coasts and This Study. All Measurements Represent Total Length in mm.
T otal Length in mm a t Age: Worker Location 1 2 3
Welsh and Breder (1923) New Jersey 150 220 265 Haven (1957) V irginia 175-180 Higgins and Pearson (1927) Pamlico Sound, N. Carolina 180 240 Hildebrand and Cable (1930) Beaufort, N. Carolina 143.4 Bearden (1964) S. Carolina 120-130 Hansen (1969) Pensacola Bay, Fla. 120 Nelson (1969) Mobile Bay, Ala. 117 165-175 Roithmayr (1965) Northern Gulf 120 170 195 Parker (1971) Lake Borgne, La. 163 Suttkus (1954) Lake Pontchartrain, La. 145 Herke (1971) Marsh Island, La. 200 Parker (1971) Galveston Bay, Tex. 120-143 Pearson (1929) Texas 180 240 280 This Study Caminada Bay, La. 140-150 180-210 ----- Mean 149 206 247 131 132
The purpose of my work with the Atlantic croaker was not to duplicate or attempt to verify past studies but to determine those aspects of the life history necessary to estimate croaker production.
To determine a croaker production estimate, the seasonal change in croaker standing crop biomass, numbers at various intervals during the year and seasonal croaker growth rates are needed. Since growth rates vary from one coastal region to another, the growth rate of
Atlantic croaker was calculated in the Caminada Bay area. I deter mined growth rate by analysis of length-frequency distributions and verified this by scale analysis. The validity of using scale analysis as a technique for assessing age and growth of southern marine fish has been demonstrated by Sundararaj (1960) on spot (Leiostomus xanthurus) in Lake Pontchartrain, Louisiana. His estimates of growth of zero age class spot using length-frequency analysis (142 mm and scale analysis (144 mm) were almost identical. In addition to length-frequency analysis, I determined a length-weight relationship so weight of croakers at various lengths could be calculated.
Estimate of Growth from Length-Frequency Distribution
I have estimated growth rate for Age Class 0 and I croakers based on length-frequency analysis. No Age Class II fish were taken in this study presumably because croakers remain in offshore waters after spawning at the end of their second year (Gunter, 1945). Esti mates of seasonal growth from July 1971 to June 1972 are presented in Table 16. Length-frequency distributions used in the analysis are presented in Table 17 and Figure 31.
P o stla rv a l croakers were f i r s t c o lle cte d in November 1971 a t Figure 31. Seasonal length-frequency distributions of Micropogon undulatus taken in the Catninada Bay system with combined gear, July 1971 - June 1972. Total length in millimeters
20 40 60 80 100 120 140 160 180 200 220 > 0 n—i—i—i—i—r- 20 N=28 July 28,1971 10 n J----- L J~T 0 20 in i—i—r T i c i I 1 r N=I0 Aug. 28,1971 10
0 40 rn N=8 Sept. 21,1971 — 30
20
10
0
141 + 146 mm 2 Specimens Oct. 14,1971
40 N=46 Nov. 4,1971 30
20
10 0 nrn rr N=l64 Nov. 23.1971 —
n I • 141 + 146 mm 2 Specimens Oct. 14.1971
40 N=46 Nov. 4.1971 30
20
10
0 n 40 I I I I I N=I64 Nov. 23,1971 — 30
20
10
0 z - r 40 N=673 Dec. 16.1971—
30
20
10
0 30 N=255 Jan. 12.1972 20
10
0 20 N=2I0 Feb. 2,1972 — 10
0 on _n K l . r A I P - L A I Frequency in percent of sample i i n r r =7 Mr 14,1972 Mar. N=476 =0 My 17,1972 May N=400 =0 Arl 29,1972 April N=705 =4 Fb 24,1972 Feb. N=54l =9 Arl 4,1972 April N=593 =5 Jn 12,1972 Jan. N=255 =I Fb 2,1972 Feb. N=2I0 i N=2I0 Feb. 2,1972
0
20 N=54l Feb. 24.1972
10
0
20 N=476 Mar. 14,1972
10
0
10 N=593 April 4,1972
0
10 N=705 April 29,1972
0 20 N=400 May 17,1972 10
0 20 N=I07 June 7,1972 10
0 20 N=27 June 28,1972 10
0 134 a length oC 11 mm (Figure 31). Growth of this age class was followed from November 1971 to the term in atio n of sampling in June 1972. In order to obtain estimates of a full year's growth, I had to utilize data from July 1971 to October 1971 and assume that growth rates in the same period of time (July to October) in both years were similar.
Parker (1971) found th&t croaker growth rates in Galveston Bay in
1963 and 1964 were nearly identical so assuming growth rates were sim ila r in 1971 and 1972 may not be u n r e a lis tic . From November 1971 to April 1972 (the period of recruitment), the apparent growth rate was repressed by the immigration of new postlarvae into the study area.
This is apparent by inspecting the mean length from November to A p ril in Table 17. Numerical abundance and growth rate increased until May
1972 (Figure 31 and Table 16). A fter May, numbers and growth ra te s decreased rapidly. From May to October, emigration was occurring as croakers began moving offshore.
Seasonal growth rates were determined by plotting growth in creases between each sampling period and combining for each season of the year (Table 16). From November 1971 to la te February 1972, growth rates were approximately 15.0 mm per month when croakers ranged in length from 25 to 38 mm (Table 17). From late February to mid May, when croakers ranged in mean length from 38 to 89 mm, growth rate was higher at 19.3 mm per month. From mid May to late
July, when croakers ranged in mean length from 89 to 122 mm, growth rates decreased to 11.3 mm per month. From late July to October with croakers ranging from 122 to 148 mm, growth rates were 9.2 mm per month. The highest growth rate occurred in the spring months. This 135
was probably partially attributable to an optimum growth temperature
and maximum food availability. The mean monthly growth rate from
July 1971 to June 1972 was 12.0 mm. Inspection of Figure 31 and
Table 17 reveals that croakers reached a total length of 140 to 150
mm in October 1971 when they were approaching one year of age (assum
ing they were spawned in October or November of the previous year).
Croakers la rg e r than 150 mm were takenfrom Ju ly to November
1971 and February to June 1972 (Figure 31). No croakers greater than
150 mm were taken from November 1971 to February 1972. Apparently
this size class had either moved back offshore to spawn or grown
large enough to evade capture. These were probably Age Class I fish
approaching two years of age. Only29 of the 5,300 croakers taken were Age Class I fish or older. In the late summer and early fall,
the majority of Age Class I fish were 180 to 210 mm total length
(Figure 31) and I feel this is the length attained at two years of
age. One specimen taken in November 1971 was 195 mm and was probably
a two year old croaker having been spawned in the fall of 1969.
Scale Analysis
The use of annual circuli or annuli on scales as an indicator
of yearly growth is a standard practice in fishery biology. This
method has been used in aging southern marine fish by Sundararaj
(1960) with spot in Lake Pontchartrain, Louisiana, Suttkus and Sun
dararaj (1961) with Gulf menhaden off the mouth of the Mississippi
River, and Hansen (1969) with pinfish in Pensacola Bay, Florida.
This method was tried in order to verify my estimated growth rate
determined from length-frequency analysis. 136
Table 16
Estimate of Age Class 0 Croaker Growth Rate Derived from Length-Frequency Data (1971-2)
Mean Increase Range of per Sampling Increase L argest In crease Period (mm) per Sampling Period Fish (mm) (mm) (3 weeks) Month (mm)
Nov. 4-Nov. 23, 1971 43-48 5 Nov. 23-Dec. 16 48-63 15 Dec. 16-Jan. 12, 1972 63-73 10 11.0 15.0 Jan. 12-Feb. 2 73-88 15 Feb. 2 -Feb. 24 88-98 10
Feb. 24-Mar. 15 98-113 15 Mar. 14-Apr. 4 113-133 20 13.0 19.3 Apr. 4 -Apr. 29 133-143 10 A pr. 29-May 17 89-96* 7
May 17-Jun. 7 96-106 10 Jun. 7-Jun. 28 106-111 5 8.7 11.3 Jun. 28-Jul. 28, 1971** 111-122 11
Jul. 28-Sep. 21 122-142 20 Sep. 21-0ct. 14 142-145 3 7.6 9.2
*Mean length used from May to October as indicator of growth.
**It was necessary to use growth estimates derived from 1971 sampling from July 28 to October 14 in order to estimate one year's growth. Sampling terminated in June 1972 and it was assumed that growth rates in both years were similar. Tab le 1'7
Length Frequency Distribution of Age Class 0 Atlantic Croaker from July 1971 to June 1972. Data R epresents A ll S ta tio n s and Gear Combined.
T o ta l July Aug. Sept. Oct. Nov. Nov.Dec. Jan. Feb. Feb. Mar. Apr. Apr. May June June Length (mm) 28-29 28-29 21-22 14-16 4-5 23 16 12-13 2 24 14-15 4 29-30 17-18 7-8 28-29
11-15 3 2 16-20 9 13 21-25 18 42 26-30 4 61 31-35 9 27 36-40 0 13 41-45 5 46-50 '""-I- 51-55 56-60 61-65 66^70 71-75 76-80 81-85 86-90 91-95 96-100 1 101-105 1 106-110 4 111-115 2 116-120 2 121-125 3 1Z6-130 3 131-135 2 136-140 2 141-145 2 3 1 1 2 146-150 2 3 1 1 1
Mean Length 122 148 142 145 25 28 27 34 38 35 38 63 89 96 106 111 T otal Number 22 2 7 2 46 164 673 255 210 540 476 593 703 400 102 22
Straight lines indicate estimated growth between sampling periods. Lines connect largest individuals while recruitment is occurring (Nov. to April) and means after emigration has started (May toOct.). VjJ ->3 138
Although the to ta l number of scales I examined was not la rg e ,
I feel that the results I obtained were adequate to substantiate my
length-frequency data. The age of fish as indicated by scales con
formed to that indicated by length-frequency data. Scale samples were taken from 8 croakers between 140 and 150 mm and 3 croakers between 177 and 228 mm. Five to ten scales from each fish were examined. Occasionally regenerated scales were found which were not used in age determination. All scales were removed from an area just
above the lateral line immediately behind the left opercle.
Scales taken from croakers between 140 and 150 mm in September and October 1971 showed one distinct annulus near the edge of the anterior field. This indicated these fish were approximately one year of age. In most cases the annul! were located either right on
the edge of the scale or within 3 to 4 circuli of the edge. The best
criteria of the croaker annulus were "crossing over" and adjacent zones of closely spaced circuli and widely spaced circuli.
Scales from the 3 specimens th a t were 177 to 228 mm also showed
distinct annulus formation. The 177 mm fish had a definite annulus
6 circuli from the edge of the anterior field which indicates the fish was over one year old. It was taken on February 24, 1972, at station
6 and was probably spawned in the fall of 1970. The scales from two
specimens th a t were 220 and 228 mm had two annul!. For both fis h , the
first annulus was about two-thirds of the distance from the focus to
the edge of the anterior field. The second annulus was 8 circuli
from the edge of the anterior field for the 228 mm specimen and 3
circuli from the edge of the anterior field for the 220 mm specimen. 139
This p a tte rn of annuli in d ic a tes these two fis h were over two years of age and supports my length frequency data for two year old croaker which I had estimated were between 180 and 210 mm.
Length-WeiRht Relationship
The determination of.a length-weight relationship was necessary
in order to convert length into weight in growth calculations. This relationship may be expressed as follows:
log w = log a + n log 1
where w = weight in grams
1 = length in millimeters
a + n = growth constants
Calculations were made on 213 croakers from 51 to 220 mm collected at a l l s ta tio n s from May 1971 to A p ril 1972 (Table 18). The constant a may vary due to differences in season, habitat, sex, or maturity while n will be nearly constant throughout the year (Tesch, 1971). The exponent n will nearly always be between 2 and 4, often close to 3.
If n > 3, the fish becomes "heavier for its length" as it grows larger
(Tesch, 1971). The following regression was calculated from monthly samples representing croaker taken throughout the year:
log w = -5.5082 + 3.2454 log 1
Calculated and empirical data were plotted (Figure 32) and compared.
There was a very close agreement, particularly at the shorter length intervals. This relationship was used in determining the mean weight of croakers at given mean lengths and was calculated for croakers ranging from 55 to 220 mm to t a l length. Table 18
Length-Weight Relationship - Micropogon undulatus - Caminada Bay Area - May 1971-April 1972
Class X Log L In te rv a l Total X Weight X Calc. (mm) Number Length (g) Log L Log W Log W (Log L)2 Log W Calc. W. Diff.
51-60 7 55 1.50 1.7403 .1760 .3063 3.0286 .1398 1.4 -.1 0 61-70 12 66 2.60 1.8195 .4149 .7549 3.3106 .3968 2.5 -.10 71-80 20 75 3.55 1.8750 .5502 1.0316 3.5156 .5769 3.8 -*-.25 81-90 22 85 5.56 1.9294 .7450 1.4374 3.7226 .7535 5.7 + .14 91-100 21 97 8.48 1.9867 .9284 1.8445 3.9470 .9394 8.7 + .22 101-110 28 105 10.67 2.0211 1.0281 2.0779 4.0848 1.0511 11.2 + .53 111-120 26 115 14.90 2.0607 1.1731 2.4174 4.2465 1.1796 15.1 + .20 121-130 16 128 20.99 2.1072 1.3220 2.7857 4.4403 1.3305 21.4 +.41 131-140 12 136 25.90 2.1335 1.4133 3.0153 4.5518 1.4159 26.1 +.20 141-150 22 145 30.65 2.1613 1.4864 3.2126 4.6712 1.5061 32.1 +1.45 151-160 4 156 40.50 2.1931 1.6074 3.5252 4.8097 1.6093 40.7 + .20
161-170 3 164 49.03 2.2148 1.6904 3.7439 4.9053 1.6797 47.8 -1.23 i 171-180 7 174 62.34 2.2405 1.7947 4.0210 5.0198 1.7631 58.0 -4.34 181-190 8 185 70.18 2.2671 1.8462 4.1855 5.1397 1.8494 70.7 + .52 191-200 0 - 201-210 4 205 101.53 2.3117 2.0065 4.6384 5.3440 1.9942 98.7 -2.83 211-220 1 220 124.80 2.3424 2.0962 4.9101 5.4868 2.0938 124.1 -.7 0
£213 £33.4043 £20.2788 £43.9077 £70.2243
Calculations: (1) Log W = log a + n log L 1np a _g_l°g w x e(log L) - e Log L x e (Log L x Log W) ' ; 8 N x e (Log L)* - (e Log L)2 _ -42.6415 = 7.7415 5.5082 (3) n = e L°g W - CH x Log a) = 20.2788 - (-88.1312) = 3>2454 e Log L 33.4043
(4) Log W = -5.5082 + 3.2454 Log L -p~ o Figure 32. Length-weight relationship, Micropogon undulatus, Caminada Bay system, May 1971 - April 1972. Average Weight (grams) 140 160 120 100 0 _ 80 60 Calculated Data• EmpiricalA Data 100 Total Average Length (mm) 120 140 6 180 160 200 220 141 142
Fish Production
From the standpoint of bioenergetics, an estimate of fish pro duction is a more valuable and meaningful measurement than is the standing crop biomass. There have been a considerable number of esti mates of standing crops of estuarine fishes but very few production estimates. Calculation of fish production is useful from the practical standpoint in that it provides an estimate of potential fishery yield as well as the theoretical knowledge of the amount and percentage of energy transferred from the primary producers to the upper trophic levels of the fish. Fish production in the deltaic estuaries sur rounding the mouth of the Mississippi River has never been determined.
I would like to clarify the difference between biomass and pro duction. Biomass is the unit weight of fish found in a defined area at any one time. Production is the rate of increase in biomass
(weight) through growth or reproduction, while the fish are in a defined area in a given period of time. The key difference between biomass and production is the "rate of increase" which refers to the formation of new organic tissue during a given period of time. The term production should not be confused with yield which refers to that portion of the total production which is harvested by man and not what is totally produced (Ricker, 1971).
A summary of estimates of standing crop biomass in estuarine and marine ecosystems is presented in Table 19. Reported estimates of standing crop biomass were generally higher and underwent less fluctuation in the Gulf region than on the Atlantic coast. The highest estimates were reported by workers using drop nets. Estimates derived by Hellier (1962), Kjelson et al. (1972), Hall and Woodwell Table 19
Estimates of Standing Crop Biomass in Estuarine and Marine Ecosystems
Biomass (wet weight) Location Author Method g/m^ lb /acre
Laguna Madre, Texas Hellier (1962) Drop net quadrat 2.0 to 37.8 18 to 337.2 Redfish Bay, Texas Hoese 6 c Jones (1963) Drop net 0.46 to 4.9 4.1 to 43.6 Guadalupe Bay, Texas Mosely 6e Copeland (1969) Drop net 3.0 to 231 26.7 to 2055.9 Mustang Island, Texas McFarland (1963) Beach seine 2.9 to 11.6 25.8 to 103.2 Corpus Christi Bay, Texas Jones et al. (1963) Helicopter borne purse net 5.07 to 18.7 45.1 to 166.4 Mississippi River Delta Kelley (1965) Rotenone .14 to 29.1 1.22 to 258.8 Bermuda Reef Bardach (1959) Visual observation w ith scuba 49 436.1 Newport River Estuary N. C arolina Kjelson et al. (1972) Drop net 0 to 72.2 0 to 642.6 Flax Pond, New York H all 6 c Woodwell (1971) Drop net 0 to 200 0 to 1780.0 Caminada Bay, La. Regular Marsh 6 c Bay Sta. Wagner (1973) Trawl .37 to 2.97 3.3 to 26.4 If Seine .17 to 17.07 1.5 to 151.9 II Trammel net 1.49 to 5.93 13.3 to 52.8 If Combined gear .35 to 4.37 3.1 to 38.9 Enclosed Tidal Ponds II Antimycin 13.8 to 46.1 122.8 to 410.3 144 (1971) and particularly Moseley and Copeland (1969) were higher than my biomass estimates for Caminada Bay. This could be attributable
to at least three factors--higher biomass, gear selectivity, or
sampling of transients. I do not feel that fish biomass in the
Caminada Bay area is actually lower than in Texas, North Carolina,
or New York. Higher fishery harvest from Louisiana supports this
contention. Gear selectivity and sampling of transients are probably
the major reasons for the higher estimates in these regions. The
drop net was found more effective than a haul seine in estimating biomass (Kjelson £t a l., 1972). The seasonal peak reported by Moseley and Copeland (1969) was attributed to sampling local transient popula
tions of Brevoortia patronus. McFarland (1963) used a beach seine in his work and found similar levels of biomass as I did in my study.
I would like to emphasize that the estimates of fish production
in estuarine areas are minimal and are probably much lower than the
true production. I feel that production estimates of other workers have largely underestimated the fertility of coastal areas. This was definitely true in my study because of the extreme difficulty
in obtaining accurate quantitative samples and the selectivity and
sampling bias of the gear used. Most of the fishes found in estu aries undergo seasonal migrations and are therefore growing for at
least part of the year outside the estuary. As a result, the area
occupied by a population at any one time is seldom known with pre
cision. No estimates were made of natural or fishing mortality
(yield) which accounts for a large part of the total production.
The production of those fishes that are either too small or too large for capture, of those that die, and of those that emigrate was not measured. Both Greze (1967) and Mathews (1970) have pointed out that the greatest part of production is contributed by the small fish of Age Class 0 which are either not harvested by man or are too small
to be vulnerable to capture. Greze (op. cit.) found that about 75% of the production of Neogobius melanostomus in the Sea of Azov is attributable to individuals under 10 grams. This species attains a total weight not more than 40-50 grams. Mathews (op. c it.) found that
in four populations of fish in the River Thames the most productive part of the population was young-of-the-year fish not fully vulnerable to the net. Regardless of these difficulties in estimating production,
I feel it is a problem which must be attacked if we are to understand how productive deltaic estuaries are.
Production may be estimated in a direct way either graphically or numerically or indirectly from primary productivity data. The
former method requires data on growth and numbers of fish over certain
intervals of time while the latter requires a knowledge of available energy from primary production and transfer efficiency to the trophic
levels of fish. The first involved direct measurement of production of Age Class 0 Atlantic croakers by the Allen graphical method (1951) and the Ricker numerical method (1946). The second is an indirect estimation of potential annual fish production based on the transfer
of organic matter from primary production after the method of Ryther
(1969) and Wiley (1972). I have also calculated P/B or production: biomass ratios which are an indication of the amount of growth occurring
during a given time period and the rate of turnover of organic tissue. 146 Direct Estimate of Age Class 0 Atlantic Croaker Production
Allen graphical method
Allen (1951) found that the production of an age class in a fis h stock in a sm all u n it of time At is the product of the number of fish present (N), and the mean weight (w). The production (P) in a small unit of time (At) would be equal to NAw, where Aw is the growth in mean w eight of the population in the time in te rv a l (Chapman,
1971). By summing all measurements made through the year, an estimate can be made of total production of the year class. The curve relating numbers and mean weight of an age class is called an Allen Curve.
Figure 33 is an Allen Curve of Age Class 0 croaker production from
1971-72. After May 17, Figure 33 demonstrates the classical Allen
Curve; a steady decline in number of fish taken corresponds to in creasin g mean w eight. The ir r e g u la r it ie s in the curve from November
23 to May 17 represent the period of recruitment when varying numbers of croaker were taken. The mean weight increased very slowly u n til
March when production increased rapidly reaching a peak in early May when the croakers were a mean length of 96 mm. The annual production is the e n tire area beneath the curve from November 23 to October 14 and totaled .86 g/m^/yr. Details of these calculations are presented in Table 20. Production of Age Class 0 croaker is also presented in
Figure 29 which represents the relationship of production, biomass and number of croakers taken with combined gear. It is again evident production is either zero or very low during the winter period but increases rapidly from March to mid May after which it decreases rapidly during the summer. The May peak in production occurs F igure 33 Allen curve of Age Class 0 Micropogon undulatus production, Caminada Bay system, 1971-2. Number of fish c .350 250 200 550 600 400 150 300 450 500 650 100 700 0 e 16 Dec o 23 Nov a 12 Jan a / Ar 29 Apr / Mar e 2 Feb e 24 Feb 4 r p A 5 en ih (rms w s) (gram eight w Mean a 17 May 10 u 7 Jun u 28 Jun 15 J 28 u I 20 et 21 Sept c 14 Oct 147 Table 20
Atlantic Croaker Production (Age Class 0) in the Caminada Bay System (1971-2)
Derived from A lle n 's G raphical Method
CM 4 = /*\ c CO o ' —/■ t 4 4J u c m O CM « , 6
w 3 e (mm) TT in* (mm) l NAw O P , o'js IJ T i Sampling Sampling Period Production (P) Length Length Increase Change Change in Mean Length Length Increase P/B Mean Mean Weight (g) Number (N) Mean Mean Length Mean Length Plus PL. CO Weight Weight Aw
Nov. 4 - Nov. 23 5 25 30 .25 .25 45 11.25 .0014 .0014 1.0 Nov. 23 - Dec. 16 15 28 43 .64 .39 164 63.96 .0081 .013 .62 Dec. 16 - Jan. 12 10 27 37 .40 -.2 4 673 -161.52 -.021 .034 0 Jan. 12 - Feb. 2 15 34 49 .98 .58 255 147.90 .019 .032 .59 Feb. 2 - Feb. 24 10 38 48 .95 -.03 210 - 6.30 -.001 .025 0 Feb. 24 - Mar. 14 15 35 50 1.00 .05 540 27.00 .003 .068 .04 Mar. 14 - Apr. 4 20 38 58 1.90 .90 476 428.40 .055 .115 .48 Apr. 4 -Apr. 29 10 63 73 3.40 1.50 593 889.50 .113 .257 .44 Apr. 29 - May 17 7 89 96 8.00 4.60 704 3238.40 .413 .718 .58 May 17 - Jun. 7 10 96 106 11.80 3.80 400 1520.00 .194 .602 .32 Jun. 7 - Jun. 28 5 106 111 13.90 2.10 103 216.30 .028 .183 .15 Ju n . 28 - J u l. 28 11 111 122 18.50 4.60 22 101.20 .013 .052 .25 Jul. 28 - Sep. 21 20 ' 122 142 30.00 11.50 22 253.00 .032 .084 .38 Sep, 21 - Oct..14’ 3 142 145 30.65 .65 7 4.55 .001 .027 .04 Total for year 6746.24
Total production: 6746.24 g. fish tissue Sampling area of combined gear: 7842 m2 6746.24 g/7842 m2 = .86 g fish tissue/m2/yr wet wt.
00 149 just after the peak in numerical abundance and at the same time that biomass is reaching a seasonal peak.
In Table 20, growth estimates presented in Table 16 were used to determine the mean length and the length increase for each period and the mean weight was determined from the length weight equation c a lc u la te d in Table 18. The mean length rep resen ts the average length at the beginning of the sampling period while the mean length plus the length increase represents the length at the end of that period.
The difference between the two is the increase in length due to pro duction. The mean weight was determined for the length at the end of each period. The change in mean weight (Aw) was the difference be tween the mean weights of successive sampling periods. The product of the number of croakers taken in each period (N) and the change in mean weight in each period was the production for that period. Two periods of "negative" production are apparent on January 12 and
February 24. Although it is obvious that true growth is not negative, it is possible to get negative figures in calculation of production due to apparent mean weight loss caused by recuitment of‘postlarval croakers into the study area. The negative values of production were summed together with the new production of tissue in the final estimate. Production for each sampling period totaled 6746.24 grams organic matter which was divided by the combined gear sampling area of 7842 m^ to give an estimate of .86 grams fish tissue/m^/year wet wt.
Production-biomass or P/B ratios were then calculated from these data. The production per m^ per sampling period was tabulated o as well as the biomass (B) per m which was taken as the product of 150
N and w. The relation between the production in a time interval and
the weight of the fish at the beginning of the time interval is an expression of the rate of growth that has occurred in that period and the percentage of the biomass that is produced through the formation of new organic tissue. The P/B ratios were highest in the early stages of life and give a useful indication of the productivity of the age class in different phases. It was highest in November when croakers were of a mean length of 25 mm. This supports earlier studies, i.e. Greze (1967) and Mathews (1970) in which it was found that the most productive part of the population was in the very young stages. P/B ratios decreased until an increase in water temperature in March. The P/B ratios ranged from .04 in October fo r croakers approaching 1 year of age to 1.0 in November fo r post-
larval croakers just entering the bay. The P/B ratio was zero during the times of negative production. The mean P/B ratio for the entire age class was .41.
Ricker numerical method
Ricker (1946) formulated a method for calculating production
(P) from instantaneous growth rate (G) and mean biomass (B) during a sampling interval:
P = GB
When growth is considered to be exponential, the instantaneous growth rate is estimated by:
log e W2 - log e w^ G — ■■■' ■ At where w-^, W£ are the mean weights of fish at times t^ and t2 * The mean 151
biomass Is computed by averaging biomass estimates of adjacent sam
pling periods arithmetically (Chapman, 1971) and is represented as:
B - Bl * B2 2
The same data on population abundance, weight and growth rates used
in the first estimate of Age Class 0 croaker production were used by
this estimate. Details of the calculations are presented in Table 21.
It is evident that the mean biomass was highest in May accounting for
the peak production at that time. The instantaneous growth rate was
highest for very young croakers between 25 and 38 mm and then decreased
in late winter. It increased as did the P/B ratio in the previous
calculations from March through May when temperatures were rising.
After the May peak, production gradually declined through the summer
and into the fall as growth rates declined and croakers began their
offshore emigration. Summation of the production in each of the sam
pling periods totaled 7837.90 grams organic matter which was divided by the combined gear sampling area of 7,842 m^ to yield an estimate
of production of .99 grams fish tissue/m^/year wet wt.
Combination of Production Estimates
If the production estimates derived from these two methods
of direct computation were averaged (Tables 20 and 21), the production
of Age Class 0 ctoakers in the Caminada Bay area would be .93 grams fish tissue/m2/year wet wt. I have used this figure in all further
calculations of fish production and assume it is the most accurate based on the data analyzed and the methods utilized.
Estimate of Total Fish Production Based on Atlantic Croaker Production Table 21
Atlantic Croaker Production (Age Class 0) in the Caminada Bay
System (1971-2) Derived from Ricker's Numerical Method
•o 60 o •rl w*0 M co a) 4J to Pk 00 •H■a a
Nov. 4 - Nov. 23 0.25 11.25 58.11 .95 55.20 Nov. 23 -• Dec. 16 0.64 104.96 187.08 -.48 -89.80 Dec. 16 -■ Jan. 12 0.40 269.20 259.55 .90 233.60 Jan. 12 -■ Feb. 2 0.98 249.90 224.70 -.03 - 6.74 Feb. 2 - Feb. 24 0.95 199.50 369.75 .06 22.19 Feb. 24 -■ Mar. 14 1.00 540.00 722.20 .64 462.21 Mar. 14 -■ Apr. 4 1.90 904.40 1460.30 .58 846.97 Apr. 4 - Apr. 29 3.40 2016.20 3824.10 .85 3250.49 Apr. 29 -• May 17 8.00 5632.0 5176.0 .39 2018.64 May 17 - Jun. 7 11.80 4720.0 3075.85 .17 522.89 Jan. 7 - Jun. 28 13.90 1431.7 919.35 .28 257.42 Jun. 28 - ■ J u l. 28 18.50 407.0 533.50 .48 256.08 Jul. 28 - Sep. 21 30.00 660.0 437.28 .02 8.75 Sep. 21 - Oct. 14 30.65 214.55
Total for Year. 7837.90
Total production: 7837.90 g. fish tissue Sampling area of combined gear: 7842 m^ 7837.90 g/7842 m^ *» .99 fish tissue/m^/yr wet wt. 153
Based on the rate of production of croakers, it is possible to get a rough estimate of total fish production. Two unavoidable assump
tions must be made for the estimate to be valid. We must assume that all the other species have generally similar growth rates and are
about equally susceptible to capture with the gear used. Three of
the four essentials for this calculation have already been estimated.
These are the production of croakers (.93 g/m^/yr), the mean standing
crop biomass of croakers (.21 g/m ) and of all fish collected (16.44 g/m^). The unknown, total fish production, may be calculated as
follows. Waters (1969) defined the turnover ratio (T) as the ratio of production to mean standing crop over a time interval (At):
T = P/B
The value of T for Atlantic croakers in my study is 4.43. This is say ing in essence that 4.43 times the mean annual croaker biomass is pro duced every year. .If T = P/B has been estimated for species X, but only B is known for another species Y, then the T value for X can be multiplied by the B for Y to obtain a rough estimate of the production of the l a t t e r (Chapman, 1971). A ccordingly,
T = - i l l = 4.43 .21
4.43 x 16.44 = 72.8 g org matter/m^/yr total fish production wet weight
In terms of dry weight, total fish production would be 72.8 x .30 or
21.8 g org matter/m^/yr. This can also be expressed as lbs/acre wet and dry weight which would be 647.9 lbs/acre and 194.4 lbs/acre, respectively. The dry weights were calculated assuming the average water content of fish flesh is 70% (Cushing, 1971). This method of 154 extrapolation has been used to get approximate calculations of total fish production based on turnover ratios of one or more dominant species by H e llie r (1962) in the Laguna Madre of Texas and Mathews
(1970) in the River Thames in England.
Comparison with fish production estimates from other estuarine or marine ecosystems may be made from Table 22. The productivity that
I have reported from Caminada Bay is higher than any previous estimate made in an estuary. This was not unexpected because the estimated net primary production of the area is also higher than has been previously reported in an estuary (Kirby, 1971). One reason for such high pro ductivity is the high turnover ratio (4.43) of organic fish flesh.
Also, most of the fishes in my study were young-of-the-year fishes which had very rapid growth rates. Previous studies by other workers, i.e. Allen (1951), Hunt (1966), Greze (1967), and Mathews (1970) have shown that the greatest part of production is contributed by fishes under one year old. The very high fishery harvest of coastal
Louisiana is also higher than all other coastal Gulf regions. Moore et al. (1970) found that catches of offshore demersal fishes derived from estuarine areas were two to five times greater off Louisiana than off Texas with greatest catches coming from depths ranging from
9 to 37 meters directly offshore from Caminada Bay. Accordingly, my estimate of fish production in Caminada Bay was 4.7 times greater than that of the Laguna Madre in Texas reported by Hellier (1962).
Based on the acreage of estuarine water in the Barataria and
Caminada Bay system, it is possible to get an estimate of the total poundage of fish produced in this system in a year. Chabreck (1970) 155
Table 22
Estimates of Fish Production in Estuarine and Marine Ecosystems Based on Field Measurements
Production (wet weight) Location g/m2/y r lb /a c re /y r
Bermuda Reef Bardach (1959) Visual 17.2 153.1 observation w ith scuba Laguna Madre Hellier (1962) Drop net 15.4 137.1 Texas quadrat Aransas Pass Copeland (1965) Tide trap 57.6 512.6 Texas Flax Pond, Hall & Woodwell Drop net 60.0 534.0 New York (1971) Caminada Bay Wagner (1973) Trawl, seine 72.8 647.9 La. trammel net reported this area has 593,640 acres of estuarine water in inter mediate, brackish and saline marshes and water bodies. I have esti mated each acre produces 647.9 pounds of fish. By multiplying the estimated production in lbs/acre by the total estuarine water acreage, the minimum total yearly fish production of the Barataria and Caminada
Bay system is 384,619,356 pounds (174,826,980 kilograms).
The annual net primary production directly available to fish in a small tidal lake in Caminada Bay is 1,506 g org. matter/m water/yr dry weight (Kirby, 1971). This production is from three sources: detritus from Spartina. phytoplankton and benthic algae. A certain portion of this production is eaten by herbivores in the marsh and approximately 42% is exported by tides offshore. These losses were substracted from the total and the above figure represents only what is available to the water column. The production of fishes in terms of dry weight was estimated to be 21.8 g fish tissue/m^/year. Based 156
on this data, the estimated efficiency of conversion of net primary
production into secondary fish production is 1.4%. Considering that
62% of the fishes taken in this study are mid carnivores which are
two to three trophic levels removed from the primary producers, I
feel this is a fairly accurate approximation of the efficiency of
conversion.
Indirect Estimate of Potential Fish Production Based on Primary
Productivity Data
I have estimated actual production of fishes based on direct
field measurements. An indirect estimate of potential fish production
can be calculated based on the primary production of the area. Pre
requisites for this are data on primary production and a knowledge
of the trophic levels of the fish and the transfer efficiency of
organic matter between trophic levels. The percentage of fishes in
each trophic level is also required. This method has been used by
Ryther (1969) to estimate total annual fish production of coastal,
offshore, and upwelling regions of the world's oceans and Wiley (1972)
in estimating potential production of fishes in the Patuxent River,
Maryland. Both authors extrapolated fish production by estimating
the transfer of organic matter to trophic levels 2-4 (the fish) from
primary production.
The net primary production data used is that of Kirby (1971) which has been previously mentioned and is 1,506 g org matter/ra^
water/yr dry weight. I have calculated the percent conversion of
organic matter from primary production into the trophic levels of
the fish (herbivores; primary, mid and top carnivores) at 10, 15 and 157
20% efficiency. Not all fishes are of one trophic level so I have calculated the percent of all fishes which I took In my study belong ing to each trophic level. Minimum and maximum potential production at each trophic level was multiplied by the percentage of fish in each trophic level to give an estimate of the range in potential fish production. Details of these calculations are presented in Table 23.
Summation of the range of potential production of each trophic level yields an estimate of from 49.04 to 173.49 g/m^/yr wet wt. or
436.46 to 1544.06 lb/acre/yr wet wt. The estimate of fish production derived from field measurement is 42% of the maximum potential fish production. 158 Table 23
Potential Annual Fish Production in the Caminada Bay System of Louisiana in g organic matter/m^/year. Annual net primary pro duction available to fish in Airplane Lake is 1,506 g org mat/m^ water/year dry weight (Kirby, 1971). The wet weight of fish was calculated by assuming the average water content of fish flesh is 70 percent (Cushing, 1971).
Trophic Level of Fish Transfer Efficiency Factor % Fish of 10% 15% 20% Trophic Level
Herbivores 4.7 dry weight 150.6 225.9 301.20 wet weight 502.0 753.0 1004.0
Primary Carnivores 40.5 dry weight 15.06 33.89 60.24 wet weight 50.20 112.95 200.80
Mid Carnivores 92.3 dry weight 1.51 5.08 12.05 wet weight 5.02 16.95 40.16
Top Carnivores 98.5 dry weight .15 .76 2.41 wet weight .50 2.54 8.03
Range of Potential Production:
Minimum Maximum
Herbivores 502.0 X .047 = 23.59 1004.0 x .047 = 47.19 Primary Carnivores 50.20 X .405 = 20.33 200.8 x .405 « 81.32 Mid Carnivores 5.02 X .923 = 4.63 40.16 x .923 = 37.07 Top Carnivores 0.50 X .985 = 0.49 8.03 x .985 = 7.91
T otal 49.04 to 173.49 V. Conclusions
The Caminada Bay area of Louisiana is an extremely productive estuarine ecosystem. Although fish populations in the bay are syn chronized to an integrated complex of chemical, physical and biologi cal factors, I believe temperature is a dominant factor.The annual temperature cycle can be correlated with seasonal biomass, abundance, and distribution in the bay and has a vital influence in spawning, seasonal movements, migrations and growth of fishes. Salinity and food availability were also investigated as to their effect on seasonal biomass, abundance and distribution and were found to be directly related in that seasonal peaks occurred at the same time
(spring and summer). Factors maintaining the high productivity of the bay are the input of nutrients and freshwater from the Mississippi
R iver, continual w ater movement through tid a l exchange which cycles nutrients and detritus from the producers to the consumers, a sub tropical climatic regime, year-round photosynthesis by three types of primary producers, abundant food when postlarval fish enter the estuary, and a maximum marsh-water interface.
I have found five categories of fishes in the Caminada Bay area based on their estuarine dependency. The majority of the fishes are seasonal migrants utilizing the estuarine system as a spawning, feed ing or nursery area. This categorization includes 3 species of freshwater fishes that occasionally enter brackish waters, 3 species of semi-anadromous fishes which migrate up through estuaries to freshwater spawning grounds, 32 species of estuarine fishes that
159 160 complete their entire life cycle in estuarine waters, 40 species of estuarine dependent fishes which spawn in the Gulf but move as post larvae into the estuary where they reside through their juvenile phases, and 35 species of primarily marine fishes which are found mainly offshore but occur as occasional transients in the lower bay.
Most of the fishes taken in the commercial and sport fishery are estuarine dependent. Sixty-six percent of the fishes taken in the industrial bottomfish catches off Louisiana inhabit Caminada Bay during juvenile stages. Three estuarine dependent species (Brevoortia patronus, Micropogon undulatus, and Leiostomus xanthurus) constitute
88% of the commercial catch by weight alone.
A to ta l of 97,223 fish e s of 100 sp ecies, 82 genera, and 46 families were taken in this study. These fishes had a combined total weight of 376.1 kilograms and a mean biomass.of 16.44 g/m .
There were 63,863 fish taken with the trawl, 31,092 with the seine,
531 with the trammel net, and 1,754 with Antimycin.
Two peaks in biomass occurred, one in April and another in
August. While the April peak is composed of large numbers of small juvenile fishes of a few species, the August peak is primarily larger sub-adult fishes, fewer in number but of a wider species d iv e rs ity . Minimum biomass occurred from November to February. The range and mean biomass in g/m^ wet wt. collected with each gear were as follows: trawl, .37 to 2.97 (1.03); seine, .17 to 17.07 (4.51) and trammel net, 1.49 to 5.93 (3.58). Combined data for all three gears ranged from .35 to 4.37 g/m^.
Biomass was highest at the more saline stations closer to the 161
Gul£. Station 2, Airplane Lake, had the highest mean trawl and seine biomass of all stations (1.91 and 6.39 g/tn^, respectively), the high est numerical abundance where 32% (30,891) of all fish were collected,
the highest numerical density (3.43 fish/m^) and the greatest number of species (53). The nearshore fringing marsh-water interface zone supports higher biomass than deeper bay areas and is a key to high estuarine productivity. Biomass collected in small tidal marsh ponds was up to 16 times higher than at stations in deeper water.
Numerical abundance was highest in March due to the peak influx of postlarval fishes moving inshore. Abundance generally increased towards lower salinities due to larger numbers of juvenile fishes in the upper bay. The mean number of fish per m^ available to the trawl o increased northward through the bay to a maximum of 1.32/m at station
6. Numerical abundance fell sharply in the fall due to offshore emigration and was lowest in November. The mean number of fish caught with each gear was: trawl, .58/m2; seine, .87/m^; and trammel net,
.02/m . Dominant families taken in order of abundance were: Engrau- lidae, Clupeidae, Sciaenidae, Atherinidae, Ariidae and Carangidae.
Estuarine fish populations seem to consist primarily of large numbers of a relatively few species which are resident or estuarine dependent and small numbers of a larger group of species which are dominant offshore and primarily marine. The five dominant species in terms of total number and weight taken were Anchoa m itchilli,
Brevoortia patronus, Leiostomus xanthurus, Micropogon undulatus and
Arius felis. These five species comprised 83% of the total number and 41% of the total weight of fish taken. Anchoa m itchilli and 1 6 2
Micropogon undulatus were the only species taken on every sampling trip during the study. The other 95 species comprised 17% of the
total number and 59% of the total weight. There were 22 species taken only once and two of these are new records for Louisiana. Erotelis smaragdus civitatum and Gunterichthys longipenis were previously unknown from L ouisiana.
The majority of species taken were mid carnivores. Arranged by trophic level, there was 9% herbivores, 5% primary carnivores, 62% mid carnivores and 24% top carn iv o res. The mid carnivores made up nearly 50% of the total biomass.
Seasonal movements and migrations occurred on a year round basis either from one section of the bay to another or from the bay to off shore and vice versa. Recruitment of fishes occurred mainly from
November to April and emigration from May to October. Three types of migrations occurred: spawning, feeding or overwintering. Five migra tions were observed among the fishes in the Caminada Bay area.
Arranged chronologically through the year these were: an early spring inshore feeding migration of postlarval estuarine dependent species, a spring spawning migration through the bay into freshwater rivers by semi-anadromous species, a gradual early summer offshore spawning migration by maturing estuarine dependent fishes, a mid summer to early fall inshore feeding migration by juveniles of primarily marine species and occasional transient adults, and a fall offshore over wintering migration of all fishes except resident species and young- of-the-year recruits of estuarine dependent species.
Certain species had a very distinct seasonality, being found in the bay for only short periods of the year while others were taken 163
throughout the year. There were 13 species taken only in the spring,
19 species taken only in the summer, 4 species taken only in the
fall, 3 species taken only in the winter and 11 species taken all year. Species diversity was highest from July to October and lowest
from November to February. From Ju ly to October, the mean number
of species taken at each station was 10 while from November to
February it was 4. The highest number of species taken on any one
collection was 22 in Caminada Pass during a mass offshore migration
in November.
Areal species composition also varied considerably; some
species were taken at only one station, others at two or more and a
few at all stations. There were 12 species taken at station 0 only,
5 species at station 1 only, 7 species at station 2 only, 4 species at station 3 only, 4 species at station 4 only, 0 species at station
5 only, 4 species at station 6 only, and 10 species taken at all
stations. Fewer species were taken in the lower salinities of the upper bay. The total number of species taken at stations 0 to 6 were 47, 48, 53, 49, 34, 40, and 30, respectively.
It is evident that there is much variation in seasonal and areal species composition. The primarily marine species were taken mostly in the summer and fall in the lower bay. Some of the estuarine
species were taken throughout the year and throughout the bay. Those
species which were taken all year were essentially the same ones
that were taken at all stations. All species of this group were either
estuarine or estuarine dependent. The freshwater species were all taken in the upper bay, mostly at station 6.
Estimates of biomass and abundance were minimal due to gear 164 selectivity and samplingbias. The efficiency of any one type of gear varies for not only eachspecies but for different length classes of each species, design of the gear, water temperature, tidal stage and time of day, behavior of the fish, turbidity and bottom type. The trawl was most effective for slow moving and small benthic fishes. Of the 17 species taken only with the trawl, 13 were strictly bottom fishes. A total of 21 species were taken only with the seine,
15 of which were species associated with the surface or shallow shore line areas. Only 4 species were captured exclusively with the trammel net, all of which were large active fishes. There were 16 species taken with all three types of gear.
The seine was the most effective gear. It captured the greatest 2 w eight, the h ig h est mean biomass in g/m , the g re a te s t mean number per m^, and the highest number of species. Generally, about twice the number of species at any one station were taken with the seine as opposed to the trawl. Biomass caught by the seine was from 2 to 3 times greater than biomass caught by the trawl at stations sampled with both kinds of gear. The seine was more effective because it is less selective; it captures a wider variety of species, and it fishes the entire water column in depths less than 6 feet.
Growth rates of the Atlantic croaker were determined for cal culation of an estimate of production. Two methods were used--analysis of length-frequency distributions and scale analysis. Both methods indicated that croakers grow to a total length of 140 to 150 mm by the end of their first year of life and from 180 to 210 mm by the end of their second year. The average growth rate in the first year 165
of life was 12 mm per month while the highest rate of growth was
19.3 mm per month from March to May. Seasonal biomass, numerical
abundance, growth and production were highest for croaker in late
April and May. The great majority of croakers taken in this study were Age Class 0 fish and only 29 of 5,300 fish were older than one
year. A length-weight relationship was calculated for croakers from
55 to 220 mm total length so length could be converted into weight in growth calculations. The relationship determined was log w ■ -5.5082
+ 3.2454 log 1.
Two methods were used in calculating an estimate of fish pro
duction. The first involved direct measurement of production using
the Allen graphical method and the Ricker numerical method. The
second was an indirect estimation of potential annual fish production based on transfer of organic matter from primary production. The
estimate of croaker production derived from the Allen method was
.86 g/m^/yr wet wt. and that from the Ricker method was .99 g/m^/yr wet wt. These estimates were combined to yield an estimate for
croaker production of .93 g/m^/yr wet wt. Based on the rate of pro
duction of croakers, it was possible to get a rough estimate of total
fish production. The turnover ratio of croakers (T) is the ratio
of production to mean biomass (P/B). This turnover ratio (4.43) was multiplied by the mean biomass of all fishes taken in this study 2 2 (16.44 g/m ) to give an estimate of 72.8 g/m /yr wet wt. or 647.9
lbs/acre/yr wet wt. total fish production. This is the highest fish
production rate ever reported from an estuary. Such a high production
rate is probably attributable to the high turnover and rapid growth 166 rates of young-of-the-year fishes, the abundant food supply available through equally high rates of primary production, and near optimal physicochemical conditions.
Based on the acreage of estuarine water in the Barataria and
Caminada Bay system, a total of at least 384,619,356 pounds (174,826,980 kilograms) of fish are produced annually. Of the 1,506 g/m^ water/yr dry weight of organic matter available to the fish from primary pro duction, 21.8 g/m^/yr dry wt. of fishes are produced. The estimated efficiency of conversion of net primary production into secondary fish production is 1.4%.
The estimate of potential production based on primary pro ductivity data ranged from 49.04 to 173.49 g/m^/yr wet wt. Actual production is 42% of the maximum potential fish production.
The vast and productive estuarine marshes of Louisiana are one of our most valuable natural resources. Louisiana has a higher acreage of marshland and a higher fishery production than any other state in the country. Although the fishes that are produced in estuaries are a renewable resource, the marshlands responsible for this production are not. We are losing an average of 16.5 square m iles of co astal marsh every year due to the n a tu ra l and man-made processes of subsidence and erosion. Man's activities in the coastal zone, such as the search for new sources of oil, land reclamation for housing developments, dredging of ship channels, road building and construction of levees for hurricane protection and flood con trol are whittling away at our irreplaceable estuaries at an ever increasing rate. In the past, many considered estuaries as valuable 167 only as garbage dumps. Today, a new awareness of the value of marsh lands is being realized. If Louisiana is to maintain its prestigous position as the leader in marine fisheries production, future activi ties in the coastal zone must be managed for the benefit of the entire estuarine ecosystem and not just man alone. REFERENCES CITED
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Table 24
Analysis of Variance
Biomass and Numbers of Fish Taken with 16 Foot Trawl
Mean Square Source of Degrees of Trawl Trawl Trawl Trawl Variation Freedom Biomass Numbers Biomass Numbers
Trip 21 2.84 762423 2.08** 2.34**
Station 5 2.96 2887567 2.17 8. 86**
Error 105 1.36 326057
Total 131
**Denotes data are highly significant at P <.01. Figure 12. Biomass and number of fish taken with 75-foot bag seine at Station 0, May 1971 - June 1972. 00 00 0Q UJ K> K) Number of fish per hectare x 1000 00 00 Biomass kilograms per hectare x 10 (or grams per meter2)
5/1 5/25 6/14 7/7 7/28 8/28 9/2110/14 11/4 I 1/2312/16 1/12 2/2 2/24 3/14 4/4 4/29 5/17 6/7 6/28 Figure 13. Biomass and number of fish taken with 16-foot trawl at Station 1, March 1971 - June 1972. Number of fish per hectare x 1000 l 1 V-r-^LJ^ ol /6/6 / 52 61 77 /8 /8 /101 1/ I12 1/611 22 /4 /4 / 42 51 67 6/28 6/7 5/17 4/29 4/4 3/14 2/24 2/2 1/12 12/16 I 1/23 11/4 9/2110/14 8/28 7/28 7/7 6/14 5/25 5/7 3/264/16 7 5 4 6 2 -1971- Date Number/ha. ims kg/ha. Biomass -1972- 33 —
Biomass kilograms per hectare x 10 (or grams per m eter2) Figure 14. Biomass and number of fish taken with 75-foot bag seine at Station 1, May 1971 - June 1972. In N> Number of fish per hectare x 1000 Biomass Biomass kilograms per hectare x 10 (or grams per m eter2) o 5/7 7/7 9/21 11/23 2/2 4/4 6/7 m Figure 15. Biomass and number of fish taken with 16-foot trawl at Station 2, March 1971 - June 1972. Number of fish per hectare x 1000 24 /6 /6 / 52 61 77 /8 /8 /1 01 1/1i231/6 /2 / 22 31 44 /9 /7 / 6/28 6/7 5/17 4/29 4/4 3/14 2/24 2/2 1/12 12/16 3 /41 10/1411 i/2 9/21 8/28 7/28 7/7 6/14 5/25 5/7 4/16 3/26 911972 1971 Number/ha. ims kg/ha. Biomass Date
Biomass kilograms per hectare x 10 (or grams per meter CO- to Figure 16. Biomass and number of fish taken with 75-foot bag seine at Station 2, June 1971 - May 1972. oo 00 Number of fish per hectare x I04 Biomass Biomass kilograms per hectare (or grams per meter^ o K> Q\ 00 o fO -fct M UJ 00 S) 0 0 VI
Date Figure 17. Biomass and number of fish taken with 300-foot trammel net at Station 2, April 1971 - May 1972. Number of fish per hectare x 100
in i k
oo KJ 00
CP
OO
U1
^ o i n
Biomass kilograms per hectare x 10 (or grams per meter2)
<781 Figure 18. Biomass and number of fish taken with 16-foot trawl at Station 3, March 1971 - June 1972. Number of fish per hectare x 1000 8 — 28 24 20 264/ / 52 61 77 /8 /8 /1 01 I14I1/321 /2 2 22 31 44 /9 /7 / 6/28 6/7 5/17 4/29 4/4 3/14 2/24 /2 2 1/12 /2312/16 I I 1 1/4 10/14 9/21 8/28 7/28 7/7 6/14 5/25 5/7 6 /1 4 6 /2 3 1971 Date ims kg/ha. Biomass Number/ha. 1972
Biomass kilograms per hectare x 10 , (or grams per m ete r i J \ 0» Figure 19. Biomass and number of fis h taken w ith 75-foot bag seine at Station 3, May 1971 - June 1972. oo S? * S? z * oo N> in 00 Number of fish per hectare x (000 ro N> Biomass kilograms Biomass per hectare x 10 (grams per meter3) o o
5/25 7/28 10/14 12/16 2/24 4/29 6/28 981 F igu re 20 Biomass and number of fish taken with 16-foot trawl at Station 4, March 1971 - June 1972. Number of fish per hectare x 1000 2 — 12 18 — /6 /6 / 52 61 7777 828921/4 4 2 2 6/2 / /4 /4 / 42 51 67 6/28 8/2.8 6/7 5/17 9/2110/141I 7/77/78 4/29 I /4 6/14I 4/4 5/25 3/14 /23 12/2/24 5/7 2/2 161/12 4/163/26 9 11972 1971 18978 Date “ Biomass kg/ha.““ — Number/ha.
Biomass kilograms per hectare x 10 (or grams per meter F igure 21 Biomass and number of fish taken with 300-foot trammel net at Station 4, May 1971 - June 1972. Number of fish per hectare x 100
S’ in
S> 00
00
Si 0 0 u> in
Biomass kilograms per hectare x 10 (or grams per meter*)
881 Figure 22. Biomass and number of fish taken with 16-foot trawl at Station 5, March 1971 - June 1972. Number of fish per hectare x 1000 12 14 10 /641 57 /5 /4 / 72 /8 /1 01114 /31/611 22 /4 /4 / 42 /7 / 6/28 6/7 5/17 4/29 4/4 3/14 2/24 10/141 9/21 2/2 1/41 7/288/281/23 12/161/12 7/7 6/14 5/25 5/7 4/16 3/26 4 l i i i i r^T"r- T i i iio i i i i i i -T r--^ " T r-^ i i i i i i i i i ol 8 6 1971 — — Date ims kg/ha. Biomass — Number/ha. -1972-
Biomass kilograms per hectare x 10 (or grams per meter $ Figure 23. Biomass and number of fish taken with 75-foot bag seine at Station 5, May 1971 - June 1972. * 03 U1 Number of fish per hectare x 1000 N> w Biomass kilograms per Biomass hectare x 10 (or grams per meter2) o o •" tn O' Ni oo 5/7 7/7 9/21 11/23 2/2 4/4 6/7 061 Figure 24. Biomass and number of fish taken with 16-foot trawl a t S ta tio n 6, March 1971 - June 1972. 't Number of fish per hectare o 7 2 6 3 5 4 0 3/26 4/16 5/7 5/25 6/14 7/7 7/28 8/28 9/21 10/14 1 1/4 1 l/23| 2 / 16 I / 12 2/2 .2/24 3/14 4/4 4/29 5/17 6/7 6/28 6/7 5/17 4/29 4/4 10/141 9/21 161 1/4 8/28 3/14 / 12 .2/24 I 2/2 l/23| 2 / 7/28 7/7 6/14 5/25 5/7 4/16 3/26 1971 Date —Boas kg/ha. Biomass — — Number/ha. 1972
rBiomass kilograms per hectare x 10 (or grams per meter vO Figure 25. Biomass and number of fish taken with 300-foot trammel net at Station 6, June 1971 - May 1972. Number/ha. 2 CD Oq cn CO S> Number of fish per hectare x 100 Biomass kilograms Biomass per hectare x 10 (or grams per meter'*) © © — W O' 0 0
1971 1972 261 VITA
Paul R. Wagner was born In New Orleans, Louisiana, on February
20, 1947, and has been a life-long resident of Louisiana. He grad uated from St. Martin's High School in Metairie, Louisiana, in June
1964. From 1964 to 1970, he attended Tulane University in New Orleans where he was awarded a Bachelor of Science degree in Biology in 1968 and a Master of Science degree in Aquatic Ecology in 1970. While in graduate school at Tulane, he was supported by a teaching assistant-
ship in general and environmental biology.
In February 1970, he enrolled in the graduate school of Louisiana
State University. Since then he has been working as a research assis tant in the Department of Marine Sciences of the Center for Wetland
Resources and is currently a candidate for the degree of Doctor of
Philosophy. .
193 EXAMINATION AND THESIS REPORT
Candidate: Paul Robert Wagner
Major Field: Marine Sciences
Title of Thesis: Seasonal Biomass, Abundance and Distribution of Estuarine Dependent Fishes in the Caminada Bay System of Louisiana. Approved:
Major Professor and Chairman
D^an of tire Graduate School
EXAMINING COMMITTEE:
Date of Examination:
April 25, 1973