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Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects
1980
Age determination and growth of the blueback herring, Alosa aestivalis
Jack Gerald Travelstead College of William and Mary - Virginia Institute of Marine Science
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Recommended Citation Travelstead, Jack Gerald, "Age determination and growth of the blueback herring, Alosa aestivalis" (1980). Dissertations, Theses, and Masters Projects. Paper 1539617499. https://dx.doi.org/doi:10.25773/v5-0y24-1a56
This Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. AGE DETERMINATION AND GROWTH OF THE BLUEBACK
HERRING, ALPSA AESTIVALIS
A Thesis
Presented to
The Faculty of the School of Marine Science
The College of William and Mary in Virginia
In Partial Fulfillment
Of the Requirements for the Degree of
Master of Arts
by
Jack Gerald Travelstead
1980 APPROVAL SHEET
This thesis is submitted in partial fulfillment of
the requirements for the degree of
Master of Arts
u Jack Gerald Travelstead
Approved, January 19 8 0
Ldesch
John •lerriner
Herbert M. Austin
-'Prank J. jj Ik
Robert J. Byr)
11 TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS ...... iv
LIST OF TABLES...... vi
LIST OF FIGURES ...... vii
ABSTRACT...... viii
INTRODUCTION...... 2
METHODS AND MATERIALS ...... 4
Data Source ...... 4 Scale Characteristics and Preparation ...... 6 Otolith Characteristics and Preparation ...... 8 Data Analysis ...... 10
RESULTS ...... 14
Validity of Otolith Age Determination ...... 14 Comparison of Otolith and Scale Readings...... 15 Growth Calculations from Otoliths and Scales. . . . 17 Growth Curve Analysis ...... 19 Length-Weight Regressions ...... 20 Total Length-Fork Length Conversions...... 22 Description of Herring Creek Spawning Run ...... 2 2
DISCUSSION AND CONCLUSIONS...... 2 5
Otolith Validation...... 25 Growth Calculations ...... 26 Herring Creek Analysis...... 30
SUMMARY ...... 3 3
LITERATURE CITED...... 35
VITA...... 60
iii ACKNOWLEDGMENTS
I wish to express my appreciation to Dr. Joseph Loesch for suggesting this topic to me, for his guidance during the course of this study and for reviewing the manuscript.
I also wish to thank my committee members Dr. John Merriner,
Dr. Herbert Austin, Mr. Frank Wojcik and Dr. Robert Byrne for reviewing the final draft and for their helpful suggestions. I owe special thanks to Doug Lipton for his assistance in the field collections, laboratory dissections of the otoliths, and for the time he spent as the second reader of the scales and otoliths. I am also indebted to the personnel of the Harrison Lake National Fish Hatchery for their assistance in the field and to Mr. Fielding
Tanner for the use of his private access to Herring Creek.
I thank the personnel of the North Carolina Division of
Marine Fisheries for inviting me to participate in their anadromous fish survey aboard the R/V Dan Moore. I also express my appreciation to the following personnel from the
Virginia Institute of Marine Science: Mary Ann Vaden for the preparation of graphs; Hugh Brooks, Ken Thornberry, and
Bill Jenkins for photography? Barbara Taylor for typing the final draft and John Gourley and Jon Zernes for their help in the field and laboratory.
iv This study was funded in part from the Anadromous Fish
Act (P.L. 89-304) through the National Marine Fisheries
Service, Northeast and Southeast Regions, and the U.S. Fish and Wildlife Service, Southeast Region.
v LIST OF TABLES
Table Page
1 Mean back-calculated fork length (mm) for blueback herring males as determined from o t o l i t h s ...... 39
2 Mean back-calculated fork length (mm) for blueback herring females as determined from o t o l i t h s ...... 40
3 Summary of the scale and otolith age comparisons of344 blueback herring...... 41
4 Chi Square (x2) test of independence of age frequencies based on scale and otolith ageing methods...... 42
5 Mean back-calculated fork length (mm) for blueback herring males as determined from s c a l e s ...... 43
6 Mean back-calculated fork length (mm) for blueback herring females as determined from s c a l e s ...... 44
7 Comparison of von Bertalanffy lengths-at-age and observed mean lengths for male and female blueback herring ...... 45
8 Age and spawning frequency of blueback herring from Herring Creek for 1977...... 46
9 Mean lengths and weights of blueback herring from Herring Creek for 197 7 ...... 4 7
10 Weekly changes in mean total length, mean total weight, and mean eviscerated weight of blueback herring from Herring Creek ...... 48
vi LIST OF FIGURES
Figure Page
1 Location of fyke nets and weir sampling stations in Herring Creek ...... 49
2 Beach seine collection sites for young-of- the-year blueback herring in the James R i v e r ...... 50
3 Scales from Alosa aestivalis in age groups V, VI, and VII with an example of a regenerated scale ...... 51
4 Otoliths from Alosa aestivalis in age groups V, VI, and VII with an example of a partially crystallized otolith...... 52
5 Fork length-scale radius relationship for male and female blueback herring ...... 53
6 Fork length-otolith radius relationship for male and female blueback herring...... 54
7 Von Bertalanffy growth curves for male blueback herring derived from scale and otolith back-calculated lengths-at-age... . 55
8 Von Bertalanffy growth curves for female blueback herring derived from scale and otolith back-calculated lengths-at-age. .. . 56
9 Total weight-fork length and total weight- total length relationships for male and female blueback herring ...... 5 7
10 Eviscerated weight-fork length and eviscerated weight-total length relationships for male and female blueback herring ...... 5 8
11 Surface water temperatures in Herring Creek during the blueback herring spawning run in 197 8 starting March 21 and ending May 13. . . 59
vii ABSTRACT
Blueback herring were collected during the 1977 spawning run in Herring Creek, Virginia to: 1) validate the otolith ageing method for this species; 2) compare the level of agreement between scale and otolith ageing methods; 3) establish von Bertalanffy growth curves for each sex; and 4) contribute to the descriptive biology of blueback herring in Virginia. Of the 519 specimens examined, 459 otoliths and 442 scales were suitable for ageing.
Seasonal changes in the appearance of the otolith edge of young-of-the-year blueback herring indicated that one hyaline and one opaque zone are formed annually. In general, mean observed fork lengths-at-age agreed with mean back-calculated lengths-at-age. Agreement in age assignment between two readers was 8 2% for scales and 84% for otoliths. Scale and otolith ages agreed in 81% of 3 44 comparisons. There was no significant difference in the two age frequency distributions. The fork length-scale radius and fork length-otolith radius relationships were linear with no significant sexual differences. Mean lengths- at-age back-calculated from otoliths were larger than mean lengths back-calculated from scales, but the differences were not significant for ages 4 through 9. Mean calculated fork lengths-at-age were used to develop von Bertalanffy growth curves. There were no significant differences between these theoretical lengths-at-age and observed lengths-at-age for both scale and otolith ageing methods.
Otoliths were more efficient than scales for ageing blueback herring. The otoliths did not require sectioning or grinding because of their small size. Also, otoliths did not require cleaning, mounting, and pressing as did the scales. Thus, although otoliths required more time for removal, overall preparatory time was much less. One advantage of scales is that they provide a spawning history.
The Herring Creek spawning run lasted 5 4 days. The age composition and spawning frequency were indicative of the decline of blueback herring in Virginia.
viii AGE DETERMINATION AND GROWTH OF THE BLUEBACK
HERRING, ALOSA AESTIVALIS INTRODUCTION
Various aspects of the age and growth of the blueback
herring, Alosa aestivalis (Mitchill) have been reported.
Cockerell (1910, 1913) first described the scales of this
anadromous clupeid but did not attempt to determine age
from the scales. Marcy (1969) aged blueback herring to a
maximum of 7 years using scales and found a linear
relationship between total body length and scale length.
He used scale measurements and transverse groove count to
confirm the location of the first annulus on scales of
older fish. Beal (1968) validated the annuli of blueback
herring scales and back-calculated fork length at successive
annuli. Kornegay (19 78) has compared scale and otolith
ageing techniques for the blueback herring; the level of
agreement between the two ageing methods was 6 8%.
Kornegay's back-calculation of scale annuli, however,
tended to estimate values higher than otolith annuli measurements, especially for the younger age groups.
Netzel and Stanek (1966) and Norden (1967) , used alosine
otoliths to verify age as determined from scales but did not
provide otolith reading techniques. Norden found a close
agreement between scale and otolith readings but otoliths
from the small, landlocked alewife (A. pseudoharengus,
Wilson) were not easily accessible and were difficult to
2 work with. Von Bertalanffy growth curves were developed
for male and female blueback herring from St. John River,
Canada by Messieh (197 7) using mean back-calculated lengths
for a limited number of specimens. He determined age from
otoliths but used scales for the back-calculation of growth
Much of our knowledge of the age and growth of the
blueback herring has been established from studies of its
alosine counterparts, the alewife and the American Shad,
A. sapidissima (Wilson). Alewife age has been determined
from scales (Pritchard 1929, Odell 1934, Graham 1956,
Rothschild 1963, Norden 1967, Joseph and Davis 1965, and
Marcy 1969) and from otoliths (Netzel and Stanek 1966,
Norden 1967, and Messieh 1977). La Pointe (1957), Cating
(19 53) and Judy (1961) have fully described the growth of
the American Shad.
The objectives of this study were: (1) to validate
the otolith method of ageing blueback herring, (2) to
compare otolith and scale readings, (3) to establish von
Bertalanffy growth curves from mean back-calculated lengths
and (.4) to provide an addition to the descriptive biology of spawning blueback herring in Virginia. 4
METHODS AND MATERIALS
Data Source
This study was based on data obtained from 394 blueback herring collected from Herring Creek, Charles City County,
Virginia, between March 19 and June 3, 1977. Herring
Creek is one of the smaller tributaries to the James River with a surface area of about 1.3 km2 and runs a distance of
8.3 km from Harrison Lake to Ducking Stool Point (Figure 1).
The creek is well within the spawning ground boundaries of the blueback herring, entering the James River between kilometers 94 and 95.
Two sampling sites were established in Herring Creek.
A weir was set, with wings completely blocking the stream, approximately 0.7 km above the fall line. Downstream, 5.5 km from the mouth of the creek, two fyke nets were set side by side. At low tide, the fyke nets blocked about 75% of the cross section of the creek. All nets were checked every other day until April 11, after which the nets were checked daily. All blueback herring were bagged, iced, and returned to the laboratory for processing. Surface water temperature was recorded for each collection. It was assumed that the fyke nets and weir used in this study were non-selective of blueback herring. 5
Individual total length, fork length, total weight, eviscerated weight (weight less gonads), sex, and sexual condition (unspawned, spawned) were recorded. Length was measured to the nearest mm; total length was measured with the upper lobe of the caudal fin depressed parallel to the long axis of the body. Weight was recorded to the nearest
0.1 g using a Mettler P2000 balance.
To obtain blueback herring of age class I-IV, samples were taken off the mouth of the Chesapeake Bay between
36°30,N latitude and 37°30'N latitude from March 13 to March
21, 1978. A modified 46 m wing trawl was utilized within
45 km of the beach and in the vicinity of the 10-20 fathom contours. A total of 85 specimens were collected ranging in total length from 9 8 mm to 2 45 mm.
An additional 4 0 blueback herring were taken in May,
19 77 from pound-net catches in the Rappahannock River.
These herring were selected on the basis of unusually large or small length and were processed identically to the samples from Herring Creek.
Young-of-the-year blueback were obtained from weekly beach seines on the James River from June 1977 to January
197 8. The beach seine stations were located at kilometers
95, 90, and 47 (Figure 2). Total length, fork length, and total weight were recorded for each specimen. 6
Scale Characteristics and Preparation
Blueback herring scales are thin, cycloid, usually
subquadrate structures arranged in an imbricate fashion.
The unexposed anterior field is characterized by transverse
grooves, transverse ridges, and annular markings and is
separated from the posterior field by the baseline (Figure
3a-d).
Transverse grooves are well defined lines which arc
posteriorly across the anterior field. Curvature of the
grooves is more pronounced near the anterior margin and
diminishes posteriorly until the groove approximates a
straight line, the baseline. The number of transverse
grooves is variable but seems to be related to age (Beal
1968, Marcy 19 69) and to the size of the scale (Rothschild
1963). The focus is a point midway on the baseline.
Transverse ridges are the more numerous fine crenu-
lations which roughly parallel the anterior edge of the
scale. They are often discontinuous and branching and may
be interrupted by annuli and spawning marks.
Annuli are non-ambiguous rings which follow the general
contour of the scale margin and can usually be traced
completely around the anterior field. Annuli are often
evident in the posterior field as well.
Spawning checks are scar-like marks similar to annuli which are formed by erosion of the scale during the spawning migration. They are often present in both the anterior and 7 posterior fields. Often erosion is so great that spawning checks converge at the lateral edges of the scale.
Scales of the blueback herring also have a freshwater zone. This zone is formed during the first year migration to sea (Cating 1935) and appears inside the first annulus.
Approximately 20 scales were removed from the left side of the fish just above the midline anterior to the insertion of the dorsal fin and placed in numbered envelopes.
Five scales from each fish were soaked in fresh water for several minutes then cleaned of adhering material by rubbing between the thumb and forefinger. Impressions of the cleaned scales were made in clear Kodacel acetate sheets. Scales from seven fish were placed on a single 7.6 cm x 12.7 cm sheet. The scales were held in place by heat resistant tape then subjected to a pressure of 20,000 lbs at a temperature of 76° to 82°C for 1.5 minutes. The heat resistant tape and adhering scales were removed and discarded. A legend was added to the sheets indicating date and specimen numbers.
Scale impressions were examined at 4 OX using an
Eberbach projector. The age, yearclass, number of spawning checks, and number of transverse grooves were recorded for each specimen. Of the five scales mounted, one was chosen as characteristic. Then a second reading was made to check age determinations and to measure the distances from the focus to successive annuli. All measurements used for the scale radius-body length relationship and back- calculations were made from the focus to the dorsal corner of the scale where the lateral and anterior edges meet.
Judy (19 61) used the antero-lateral radius in age
determination of Alosa sapidissima and Miller (194 6) and
Everhart (1950) used this radius in back-calculation of
body length of Thymallus signifer and Micropterus dolomieui,
respectively. Beal (1968) found that differences between
antero-lateral radius and anterior radius of blueback
herring scales were not significant.
All scales were examined by a second reader. Any
disagreements were noted and re-examined by both readers.
If reader agreement could not be established the specimen
was excluded from further analyses.
This study followed the methods of Cating (19 5 3) and
Judy (.19 61) in which ageing of the blueback herring scale
involved counting the number of annuli and spawning checks
and adding one year for the scale edge.
Otolith Characteristics and Preparation
The sagittal otoliths of the blueback herring are
laterally compressed, minute, oval structures with irregular margins and are very similar to young Clupea harengus
harengus otoliths described by Watson (1964).Anteriorly,
the otolith is deeply cleft forming a longventral rostrum
and a short antirostrum. Posteriorly, the basal end is
rounded. The proximal surface of the otolith is convex with
a deep longitudinal furrow, the sulcus acusticus, extending
from the cleft to the center of the otolith. Both surfaces 9
taper outwardly to a thin edge. The central area or focus
is that point around which deposition takes place
(Figure 4a-d).
The structure of the otolith in reflected light was
characterized by alternating light (opaque) and dark
(hyaline) bands. Although the exact time of zone formation
may vary, hyaline growth is usually associated with winter
growth and opaque growth with summer (Williams and Bedford
1974).
Otoliths were removed from each specimen by making a
vertical incision approximately 1 cm posterior to the margin of the eye. This cut exposes the brain and anterior
portion of the inner ear. Removal of the brain exposes
the sacculi in the bony recesses at the base of the skull.
Lifting of the sacculi causes the semi-circular canals to
break, dislodging the sagitta, the largest otolith. This
otolith was used for age determination. Following removal,
the otoliths were stored dry in one dram vials numbered
serially to correspond with collection records.
The otoliths were prepared for examination by placing
them in a culture dish and completely covering with
glycerin. A sixty second immersion in the glycerin
enhanced the zoned appearance. The otoliths were examined
under a zoom dissecting microscope (50X) with a black
plate base. The surface was illuminated by reflected
light in a manner described by Williams and Bedford (1974).
For each specimen, age, yearclass, number of hyaline and 10 opaque zones, and margin type (opaque or hyaline) were recorded. An otolith annulus was considered as one opaque
zone and its successive hyaline zone. All measurements for back-calculations were made from the focus, in a longitu dinal direction toward the basal end of the otolith, to successive hyaline zones.
Otoliths were examined by a second reader and those disagreements in age which could not be resolved were excluded from further analysis. An arbitrary birthdate of January 1 was assigned for all age determinations.
Data Analysis
Although the annuli of blueback herring scales have been validated (Beal 19 68), the annuli of the otoliths have not. The validation of the otolith annuli was based on criteria similar to those suggested by Hile (1941):
1. The mean lengths of age groups based on otoliths
should coincide with modes in the length frequency
distribution;
2. A regular increase in fish length should occur
with each succeeding annulus; and
3. The mean calculated length of a fish at any
annulus should closely agree with the mean actual
length of the fish of that corresponding age
group at the time of capture. 11
Chi square analysis was used to statistically compare scale and otolith ageing methods.
Back-calculated lengths at successive ages were established using a modified proportionality formula developed by Fraser (1916) and Lee (1920):
Ln - C = fjS- (L - C) where Ln is the length of the fish when annulus ’ n1 was formed, L is the length of the fish at the time of capture,
Sn is the radius of annulus ' n' at length Ln , S is the total radius of the scale or otolith, and C is the inter cept with the ordinate in the body length-scale (or otolith) radius regression.
Length-at-age data was used to construct a von
Bertalanffy growth equation (1938). The von Bertalanffy model was chose because it is an accepted growth function for many species, and it provides estimates of growth parameters which could be incorporated into stock assessment models (Gulland 1975). The basic model is:
Lt = I*, [1 - e“K(t_to>] where Lt is length-at-age t, is the asymptotic length of the fish, i.e., the average maximum size, K is the rate at which length approaches Loo r an<^ t0 is the hypothetical time at which the blueback herring would have been of zero 12 length if it had always grown according to the established equation.
Estimates of the parameters and K were obtained from a computer program developed by Fabens (1965). This version of the size-increment method fits the von
Bertalanffy model by the least squares method using data on growth increment in known time intervals but makes no assumptions about absolute age. The model is written as:
L t = Loo (1-be -Kt) where b is an estimate of the theoretical proportion of potential growth in length that occurs after hatching.
The estimates of Lw obtained from the Fabens growth model were used as initial values in Beverton's (195 4) expression:
loge (Loo - lt) = loge LOT + KtQ - Kt where a graph of loge (LTO - lt) against t is sensitive to changes in L^. Additional values of were then substituted into the equation to obtain the best line
(highest r2). The value of K was determined from the slope of the line and tQ was obtained from:
tQ = (a - loge LoJ/K where a is the y-intercept.
Length-weight curves were obtained from the power function: 13
W = aLb where W is weight, L is length, and a and b are constants.
The least squares linear representation is:
logio W = log10a + blog10L and the regression of log10W on log10L was used to estimate the values of a and b.
f BRA of tfsa Fcy'X ( ViRGJNIA iWSTiTUTE \ \ Of MARINE SCitf- 14
RESULTS
Validity of Otolith Age Determination
Examination of the seasonal changes in the appearance of the otolith edge indicated that only one opaque and one hyaline zone are formed each year* The first zone to appear on the otoliths of blueback herring is opaque.
Young--of-the-year, collected from August through October, showed a distinct opaque nucleus with no hyaline margin.
The radius of the otolith at that time was 0.45 to 0.6 9 mm.
Beginning in November, most juveniles had formed the beginning of a narrow hyaline zone at the edge of the otolith. This was regarded as the beginning of the first annual hyaline zone, but for ageing purposes was not counted until January 1 of the next year. Juvenile herring taken in late January had otolith radii that ranged from 0.65 to 0.81 mm and showed an increase in the width of the hyaline margin.
All specimens taken during the spawning run, from
March to May, had deposited hyaline marginal zones, but no substantial increase in the width of the margin occurred over these months. While complete monthly data were not available, the period of opaque zone formation probably extends from June through October and is the period of fastest growth. The hyaline zone deposition process begins 15 in November and apparently continues through the period of cold water with little growth occurring during the spawning r un.
Mean observed lengths at capture should coincide with back-calculated lengths at successive ages if annulus for mation occurs just prior to the spawning run, and if no appreciable deposition on the otolith edge occurs during the spawning migration. Data in Tables 1 and 2 show reasonably good agreement between mean lengths at capture and the back-calculated lengths. The greatest differences were in younger fish, 2 year old males (16 mm) and 3 year old females (10 mm). Tables 1 and 2 also show a general increase in fish length with each succeeding annulus. Modes of the length frequency distributions for each sex corre sponded approximately with the mean lengths of age groups.
However, due to the great overlap in the sizes of fish in adjacent age groups and the small sample sizes the mean lengths-at-age did not correspond exactly to the modes of the length frequency distributions. This criterion usually holds for only younger age groups which were not collected in the Herring Creek study. Thus, Hile*s criteria for validation of annuli are met and blueback herring otoliths are acceptable for ageing.
Comparison of Otolith and Scale Readings
Of the 519 specimens examined, 459 otoliths and 442 scales were suitable for ageing. Although, the specimens 16
were treated with great care, some scale loss did occur.
This scale loss, however, was no where near as great as
that which occurs with commercially obtained samples.
Initial agreement in age assignment between the two
readers was 82% for scales and 84% for otoliths. The
greater percentage of the disagreements was obtained from
fish above age 6. The 7, 8, and 9-year-old age groups
accounted for 73% fo the scale ageing disagreements and
57% when using otoliths.
Ageing disagreements are partly explained by the
crowding of annuli on the scales. In many cases, spawning
checks formed on the scales in later years converge with
checks of previous years making accurate age determination
more difficult. False checks also appeared on many scales,
especially between the second and fifth annuli. These
checks usually could not be traced completely around the
anterior field of the scale, but some misinterpretation
could have occurred.
As blueback herring increase in size, the widths of
alternate hyaline and opaque zones of the otolith become
increasingly smaller and less distinct and thus more
difficult to read. A splitting of the opaque zones of the
otolith was also noted. These secondary checks were
rarely seen but usually appeared during the second year of growth. They were always less distinct than the annual
hyaline zones and were usually incompletely formed. 17
Crystallinity of the otolith, although rare, was another cause of illegibility. Of 519 pairs of otoliths examined, 3% had a single crystalline otolith and another
1% had paired crystalline otoliths. Partial crystallinity also occurred (<1%) but the number of annuli could be interpreted.
Scale and otolith readings agreed in 81% of the 344 comparisons. The distribution of the agreements and disagreements by age group is shown in Table 3. Twelve percent of the otolith readings were lower than the scale readings while 7% of the scale readings were lower than otolith readings. A chi square test of independence indicated no significant difference (P>0.9) in the two age frequency distributions (Table 4).
Growth Calculations from Otoliths and Scales
The relationship between fork length and otolith radius and the relationship between fork length and scale radius were linear but not directly proportional (Figures
5 and 6). Analysis of covariance indicated no significant difference (P>0.10) between sexes for both relationships, thus the data were pooled. Least square regressions applied to the data (sexes combined) gave the following equations:
FL = -52.8 + 180.05 Rq ; r2=0.94, N = 548 and
FL = 20.8 + 0.86 Rs; r2=0.94, N = 548 18 where FL is fork length (mm), Rs is scale radius (mm x 40)
and RQ is otolith radius (mm) and r2 is the coefficient of
determination. Specimens used for the two relationships
ranged in fork length from 40 mm to 29 7 mm.
The relationships between total length and otolith
radius and total length and scale radius were also linear
and highly correlated. The least squares regressions were:
TL = -60.1 + 203.82 RQ; r2=0.94, N=548
and
TL = 23.4 + 0.97 Rs; r2=0.94, N=542 where TL is total length.
Although both the body-scale and body otolith
relationships are linear, the rates of growth (regression
coefficients) of the scales and otoliths and the correction
factors (y-axis intercepts) are quite different. This
fact is obvious upon examination of the scales and
otoliths. The otolith is much smaller than the scale and
the annuli are spaced much more closely on the otolith.
Back-calculations of length at successive ages were made from 347 male otoliths and 112 female otoliths
(Tables 1 and 2) and from 350 male scales and 89 female
scales (Tables 5 and 6). Blueback herring reached a maximum age of 9 years (as determined from both ageing methods). Back-calculation of mean length-at-age by both methods showed females to he larger than males at all ages.
In general, the mean lengths for both sexes obtained 19 from back-calculations of otoliths were larger than lengths calculated from scales. Individual t-tests of lengths-at- age determined by the two methods for each sex were not significant for ages 4 through 9 (P>0.05 for all tests).
Annual growth increments were also estimated and indicated that females grow at a faster rate than males
(Tables 1, 2, 5, and 6). Otolith calculation of mean length-at-age indicated that the most rapid growth in length of males occurred during the second year of life with annual increment decreasing each year thereafter. Growth of females was greatest and about equal during the first and second years of life. Lengths derived from scales, however, indicated that annual growth in length declines throughout life for both sexes. Lee1s phenomenon (Lee 1912) of the apparent change in growth rate was evident in the growth data for both sexes calculated from both scale and otolith samples.
Growth Curve Analysis
Fitting von Bertalanffy growth curves to mean back- calculated fork lengths resulted in the following equations:
Males (scale data) Lt = 263 (l_e-°-397(t-0.016))
Males (otolith data)
Lt = 262 (l-e“0 .46 8(t-0. 333) ) 20
Females (scale data)
L t = 290 (l-e“°-313(t+0.042))
Females (otolith data)
L fc = 280 (l-e"°-436(t-0.366))
Estimates of length-at-age were obtained from the above equations and were plotted to provide growth curves
(Figures 7 and 8).
Von Bertalanffy lengths-at-age are compared with observed lengths-at-age for both sexes in Table 7.
Analysis of variance indicated no significant difference
(P>0.75) between the theoretical and observed lengths-at- age for both ageing methods.
Length-Weight Regressions
Specimens used for the length-weight regressions ranged in total length from 53 to 336 mm, 47 to 296 mm fork length, 1.1 to 312.6 g total weight, and 5.4 to 291.0 g eviscerated weight. A power function, W = aL*5, best described all the observed weight-length relationships
(Figures 9-12). The logio-linear equations were as follows:
Total Weight - Total Length
Males: LogioTW = 3.3626 Log10TL - 5.9570; r 2=0.96, N=383
Females: Log10TW = 3.3997 Log10TL - 6.0354; r 2 = 0.98, N= 81 21
Total Weight - Fork Length
Males: Loga0TW = 3.3380 Log10FL - 5.7160; r2=0.96, N=383
Females: Log10TW = 3.4159 Log1QFL - 5.8918; r2=0.98, N=81
Eviscerated Weight - Total Length
Males: Logi0EW = 3.2060 Log j 0 TL - 5. 6059; r 2=0.97, N=383
Females: Logi0EW = 3.1995 Log10TL - 5.5953; r2=0.98, N=81
Eviscerated Weight - Fork Length
Males: Log10EW = 3.1826 Log10FL -5.3794; r2=0.97, N=383
Females: Log10EW = 3.2149 Log1QFL - 5.4603; r2=0.98, N=81
Analysis of covariance indicated no significant differences between male and female length-weight regressions
(P>0.10 in all cases). Accordingly the data were pooled and produced the following relationships:
TW = (1.070 x 10” 5)TL3*3701; r2=0.97, N=464
TW = (1. 670 x 10” 6 ) FL 3 * 3 e ^ r 2 = 0.97, N=464
EW = (2.424 x 10“ S)TL3*2096; r 2=0.98, N=464
EW = (3.700 x 10"s)FL3‘20^4; r 2=0.98, N=464 where r2 is the coefficient of determination for the logio- linear relationships. Plots of the curves are presented in Figures 9 and 10.
Estimates of asymptotic weight (Woo) were obtained from the total weight-fork length relationship and the previously reported asymptotic lengths (LM ): 22
Males (scale data)
= 263 m m ; WTO = 2 31.4 g
Males (otolith data)
Lqo = 2 62 m m ; Woo = 228.5 g
Females (scale data)
Loo = 2 90 m m ; Woo = 321.5 g
Females (otolith data)
Loo = 2 80 m m ; Wo o = 2 85. 7 g
Total Length - Fork Length Conversions
Conversion equations were developed to facilitate comparison of fork lengths reported in this study with total lengths reported in other literature. The highly correlated least squares regressions are:
TL = 0.17 + 1.13 FL; r2=0.99, N=542 and
FL = 0.12 + 0.88 TL; r2=0.99, N=542 where TL is total length and FL is fork length. The specimens used ranged from 43 mm to 333 mm total length.
Description of Herring Creek Spawning Run
Male blueback herring were first captured at Herring
Creek collection site A (Figure 1) on March 21, 1977 and upstream at site B on April 14, when water temperatures were 12.8°C and 19.0°C, respectively. The first females 23 did not enter site A until April 9 and were not taken up stream until April 15. Water temperatures on these dates were 13°C and 19.4°C, respectively. Surface water tempera ture is plotted for the spawning run duration in Figure 11.
The migration of the adult herring lasted 54 days
(March 21 - May 13) and 394 blueback herring were taken at the two collection sites. Only one spawning wave was observed during this period with peak catches of 63 blueback herring at site A on April 22 and 104 blueback herring at site B on April 27. Chi square analysis indicated that male blueback herring were significantly more abundant than females during the entire spawning migration. The ratio of males to females was 3:1 at site A and 14:1 at site B.
Females outnumbered males in only three collections from site A, but these catches were usually preceeded by larger numbers of males. Upstream, males were always significantly more abundant than females, with sex ratios reaching 18:1 at the peak of the spawning wave.
Age composition and spawning frequency were derived from scale analysis and are presented in Table 8. The modal age for blueback males taken during the spawning run was age 6, but the data indicated a co-dominance of ages 6 and
7 for females. Mean ages were 6.35 and 6.43 for males and females, respectively. The average number of spawning checks was 1.35 for males and 1.30 for females. The percentage of male virgin spawners was 65.2, 3 8.0 and 6.0 for age classes V, VI, and VII, respectively; percentages 24 for females first spawning were 100.0, 57.1, 2 8.0, and 10.0 for age classes IV, V, VI, and VII. Only 28.0% of the
Herring Creek blueback population were virgin spawners.
The maximum number of spawning checks was 4 for 7, 8, and
9-year-old males and 3 for 8 and 9-year-old females.
Mean total lengths and total weights for male and female blueback were 276 mm, 287 mm and 182.3 g, 202.3 g, respectively (Table 9). Ranges of length and weight (sexes pooled) were 249 to 314 mm total length, 217 to 278 mm fork length, 140.7 to 312.6 g total weight, and 130.4 to 255.9 g eviscerated weight. Average gonad weight was 15.0 g for males and 22.7 g for females.
Weekly changes in mean total length, mean total weight, and mean eviscerated weight are summarized in Table 10.
Regression analysis indicated no significant change in total lengths for females (P>0.50), however the regression coefficient was marginally significant for males (.01 Eviscerated weights also decreased significantly for males (PcO.001) and marginally for females (.01 DISCUSSION AND CONCLUSIONS Otolith Validation Use of the otolith as an ageing structure for blueback herring was validated. Examination of the seasonal changes in the otolith indicated that one hyaline and one opaque zone is formed each year. Lengths and ages determined from otoliths were similar to those calculated from scales and were in agreement with empirical length-at-age data. It is also concluded that the otolith is a practical ageing structure. Traditionally, blueback herring in the Virginia fishery have been aged from scales. Scales are large and relatively easy to collect but fishing and handling techniques tend to remove scales from the specimens. Thus, key scales are difficult to obtain. In this sense, otoliths are a more permanent ageing device. Although otoliths are small and require more time for removal, they do not require cleaning, mounting, and pressing as do the scales. With experience, dissection time of the otolith was greatly reduced and total preparation time was less than that for scales. Reader agreement for both scale and otolith ageing methods was approximately equal. The difficulty of interpreting the annuli of older fish, however, was more 26 pronounced in scales because of the erosion and absorption of the scale edge during the spawning migration. The otolith annuli also become less distinct with age, but overlap and convergence of annuli was not seen at the basal end of the otolith and interpretation of their annuli was less subjective. Growth Calculations The linearity of the blueback herring body-otolith relationship in the present study is contrary to that reported by Kornegay (1978). He found a curvilinear relationship between fork length and otolith radius. Kornegay also reported significant sexual differences in the log-linear fork length-otolith radius regressions. His low coefficient of determination (r2) for males (0.29), however, suggests a very poor fit to the data; the r2 for females was 0.97. The correction factors calculated from the body-scale and body-otolith regressions represent necessary mathematical parameters but do not correspond to the morphological length of the fish at the time of scale and otolith formation although these parameters do frequently have a value near the length of the fish when scales (and otoliths) are first formed (Hile 1970). The correction factor, 20.8 mm fork length, used in this study is roughly equal to the blueback herring length at scale formation (25.0 mm total length), reported by Mansueti and Hardy 27 (1967) . The correction factor calculated for the otolith back-calculations was -5 2.77 (-60.1 mm total length). Although this does not represent a true morphological length it does indicate that the otoliths are probably present upon hatching. Most species of fish have otoliths when hatched since they must be able to orient themselves in their environment immediately upon hatching (Williams and Bedford 1974). Kornegay (197 8) found significant differences between blueback herring male and female body-scale regressions with correction factors of 75.74 for males and 29.84 for females. Beal (1968) calculated a correction factor of 37.97 for the fork length-scale regression for blueback herring from Rappahannock River commercial samples. However, his data lacked specimens between 100 and 200 mm. Marcy (1969) calculated a factor of 77.7 2 for a total length-scale radius relation for Connecticut River blueback herring. Apparently Marcy*s data were more variable since r2 for the relation was 0.60. Also Marcy (1969) used scales from the left side above and below the midline at the level of the vent as opposed to above the midline at the insertion of the dorsal fin. Geographic variability as well as the varied position of the key scales could account for the differences of the body-scale regressions. Hile (1970) suggested that a species body-scale relation rarely exists. Differences in back-calculated lengths computed from scales and otoliths were especially pronounced for ages 1 28 and 2 and were attributed to the arbitrary position of the first and second annuli on many of the scales. The first annulus was especially indistinct. Erosion of the scale edge during spawning may account for the underestimation of lengths-at-age as compared to lengths calculated from otoliths. Beal (19 68) compared calculated lengths-at-age of virgin spawners with repeat spawners to test the extent of marginal erosion on blueback herring scales. In most cases the lengths of virgin spawners were greater than the lengths of repeat spawners, however, the differences were not statistically significant. Greatest differences in growth increment were again associated with the second year and were probably a function of the arbitrary placement of the second annulus on the scales. The occurrence of Lee1s phenomenon in the data could be due to natural selection and/or size selection by the fishery. Faster growing fish of a cohort tend to mature and die earlier than slower growing members of the year- class (Gerking 19 59). Virgin blueback herring spawning generally occurs at age 4 but may occur at age 3 or not until ages 5 and 6 (Marcy 1969). Thus, if initial maturation is, at least in part, a function of size, fishing pressure would be greater on the faster growing members of a cohort who recruit at ages 3 and 4. The inequality of male and female back—calculated lengths, especially after the third year is most probably 29 the result of the onset of sexual maturity. Since females were larger than males at all ages greater than 3, the estimates of a larger asymptotic length (L^) but a smaller growth coefficient (K) relative to males were appropriate since the two growth parameters are inversely correlated (Ricker 1975). Likewise, this accounts for the fact that growth curves calculated from otoliths tended to approach their asymptotic length more quickly than did the scale growth curves. Scale erosion and convergence of the spawning checks on the scales causes a decrease in the distance between annuli and thus could account for the smaller K and greater Loo relative to those estimated from otoliths. Estimates of asymptotic fork length, 253 mm and 2 62 mm for males and 290 mm and 280 mm for females, and corre sponding asymptotic total lengths of 29 7 mm and 29 6 mm for males and 328 mm and 316 mm for females seemed biologically reasonable. Hildebrand and Schroeder (1928) reported an average total length of 280 mm for blueback herring (sexes pooled) in the Chesapeake Bay. Messieh (197 7), however, calculated asymptotic fork lengths of 231.33 mm for males and 259.85 mm for females from St. John River, New Brunswick. These differences lend support to a hypothesis of geographical variation in growth and possibly the existence of different stocks of blueback herring. Although mature blueback herring lengths-at-age calculated by 30 Messieh (197 7) were smaller than my estimates, his lengths at ages 1, 2, and 3 were very similar. Marked changes in the growth rate apparently occur when the fish reaches sexual maturity. Herring Creek Analysis The spawning run of blueback herring in Herring Creek for 1977 was extremely poor and indicative of total state landings. Virginia river herring landings were a record low and only 37% of the previous record low in 1976 (Loesch et al. 1977). Personal communication with dipnetting fishermen concurred that the seasonal run was very poor. Peak catches of blueback herring were taken when water temperatures approximated the range of 21 to 24°C reported by Bigelow and Welsh (1925). However, spawning blueback were first taken when surface water temperatures were considerably lower (12°C). Spawning blueback were also taken when temperatures fell below this range during the first week of May at the end of the spawning season in Herring Creek. Loesch and Lund (197 7) also report spawning of blueback in Connecticut at temperatures considerably below this range. The high ratios of males to females taken in Herring Creek (3:1 site A; 14:1 site B) may indicate that males remain on the spawning grounds for a longer period of time while females return to sea immediately after spawning. 31 Loesch and Lund (19 77) reported temporal and spatial variation in the sex ratio of spawning blueback herring in Connecticut, and based on day of spawning run entry they estimated a 2:1 ratio of males to females on or near the spawning ground. Joseph and Davis (19 65) previously reported an equal sex ratio in blueback herring in the lower Chesapeake Bay while Loesch et al. (19 77) reported a sex ratio of 1.7:1 for blueback herring in the James River. The high frequency of six-year-old blueback herring and the absence of four-year-olds is further evidence of the decline of blueback herring in Virginia reported by Loesch et al. (1977). Prior to 1976, age 4 blueback herring were generally the dominant yearclass in the fishery (Hoagman and Kriete 1975). A mean age of 6.4 and mean number of spawning checks of 1.34 determined from scales (sexes combined) is slightly higher than the 5.6 mean age and 0.6 0 mean number of spawning checks reported by Loesch et al. (1977) for commercial samples of blueback herring taken from the James River. The mean fork lengths and mean total weights of 243.5 mm and 178.3 g and 253.7 mm and 206.4 g reported for male and female blueback herring, respectively, in the James River commercial fishery (Loesch et al. 1977) are in reasonable agreement with the mean lengths and weights reported in this study. The decrease in total length of males as the spawning season progressed is possibly attributed to the late arrival of smaller fish. Cooper (19 61) found the same relationship with spawning alewife in Rhode Island. He felt this indicated that the larger adults become ripe at an earlier date than do the smaller adults. Changes in total weight may be attributed to an increase in the number of partially spent fish, especially since males remain on the spawning grounds for extended periods. Cooper (1961) also found changes in average weight for male and female alewife as the spawning run progressed. Changes in eviscerated weight are supported by the fact that blueback herring do not feed during the spawning run. SUMMARY 1. Otoliths were more efficient than scales for ageing blueback herring. Although the otoliths required more time for removal, overall preparatory time was much less. 2. Seasonal changes in the otolith edge of young-of-the- year blueback herring indicated that one hyaline and one opaque zone are formed annually. 3. Agreement with Hile's (1941) criteria for annulus validation suggested that otoliths were suitable for ageing blueback herring. 4. Between reader agreement in age assignment was 8 2% for scales and 84% for otoliths. 5. Ageing disagreements with scales were partly explained by the convergence of spawning checks and the presence of false annuli. 6. Ageing disagreements with otoliths were explained by the crowding of annuli after the fourth year. 7. Scale and otolith readings agreed in 81% of 344 comparisons. A chi square test of independence indicated no significant difference in the two age frequency distributions. 8. The fork length-otolith radius and the fork length- scale radius relationships were linear but not directly proportional. 9. Mean lengths-at-age for both sexes obtained from back- calculation of otolith annuli were larger than lengths calculated from scale annuli and may be due to the erosion of the scale edge during the spawning migration. 10. Mean fork lengths-at-age for scale and otolith data were used to derive von Bertalanffy growth curves. 33 34 11. The Herring Creek spawning run lasted 54 days. The age composition and spawning frequency were indicative of the decline of blueback herring in Virginia. LITERATURE CITED Beal, K. L. 19 68. Age and growth of the blueback herring Alosa aestivalis (Mitchill)„ M.A. Thesis. College of William and Mary, Williamsburg, Virginia, USA. Beverton, R. J. H. 1954. Notes on the use of theoretical models in the study of the dynamics of exploited fish populations. U.S. Fish. Lab., Beaufort, N.C., Contrib. No. 2. Bigelow, H. B. and W. W. Welsh. 1925. Fishes of the Gulf of Maine. U.S. Bur. Fish. Bull. 40 (Part I). Cating, J. P. 1953. Determining age of Atlantic shad from their scales. U.S. Fish and Wildl. Serv. Fish. Bull. 54:187-199. Cockerell, T* D. A. 1910. The scales of the clupeid fishes. Proc. Biol. Soc. Wash. 23:61-63. Cockerell, T. D. A. 1913. Observations on fish scales. U.S. Bur. Fish.Bull. 32:117-174. Cooper, R. A. 19 61. Early life history and spawning migration of the alewife, Alosa pseudoharengus. M.S. Thesis. University of Rhode Island, Kingston, Rhode Island. Everhart, W. H . 1950. A critical study of the relation between body length and several scale measurements in the smallmouth bass Micropterus dolomieui Lacdp^de. J. Wildl. Manage. 14:266-276. Fabens, A. J. 1965. Properties and fitting of the von Bertalanffy growth curve. Growth 29:265-2 89. F r a s e r , C „ M c L . 1916. Growth o f the spring salmon. Trans. Pacific Fish. Soc. 2:29-39. Gerking, S. S. 1959. Physiological changes accompanying ageing in fishes. Pages 181-211 in G.E.W. Wolstenholme and M . O ’Connor, editors. The life span of animals. Vol. 5, CIBA Foundantion Colloquia on Ageing. Little, Brown, and Co., Boston. 35 3 6 Graham, J. J. 1956. Observations of the Alewife, Pomolobus pseudoharengus (Wilson), in fresh water. Univ. Toronto Biol. Ser. 62, Publ. Ontario Fish. Res. Lab. 74:1-43. Gulland, J. A. 1975. Manual of methods for fish stock assessment Part I. Fish population analysis. FAO Fish. Tech. Pap. 40:1-154. Hildebrand, S. F. and W. C. Schroeder. 1928. Fishes of Chesapeake Bay. U.S. Bur. Fish. Bull. 43 (Part I). Hile, R. 1941. Age and growth of the rock bass, Ambloplites rupestris (Rafinesque), in Nebish Lake, Wisconsin. Wise. Acad. Sci., Arts and Letters, Trans. 33 :189-3 3 7. Hile, R. 1970. Body-scale relation and calculation of the growth in fishes. Trans. Amer. Fish. Soc. 99:468-474. Hoagman, W. J. and W. H. Kriete, Jr. 1975. Biology and management of river herring and shad in Virginia. Ann. Rep. 1975. Nat. Mar. Fish. Serv. Proj. No. AFC 8-2. Joseph, E. B. and J. Davis. 19 65. A preliminary assessment of the river herring stocks of lower Chesapeake Bay. A progress report to the herring industry. Va. Inst. Mar. Sci. Spec. Sci. Rep. No. 51. Judy, M. H. 1961. Validity of age determination from scales of marked American shad. U.S. Fish and Wildl. Serv. Fish. Bull. 61:161-170. Kornegay, J. W. 1979. Comparison of ageing methods for alewife and blueback herring. North Carolina Dept. Nat. Res. and Community Development. Spec. Sci. Rep. N o . 3 0. La Pointe, D. P. 195 7. Age and growth of the American shad from three Atlantic coast rivers. Trans. Amer. Fish. Soc. 87:139-150. Lee, R. M. 1912. An investigation into the methods of growth determination in fishes. Cons. Explor. Mer., Publ. de Circonstance 63. Lee, R. M. 1920. A review of the methods of age and growth determination in fishes by means of scales. Fishery Invest. London. Ser. 2, 4, 2. Loesch, J. G., W. H. Kriete, Jr., H. B. Johnson, B. F. Holland, Jr., S. G. Keefe, and M. W. Street. 1977. Biology and management of mid-Atlantic anadromous fishes under extended jurisdiction. Nat. Mar. Fish. Serv. Proj. No. AFCS-9-1. 37 Loesch, J. G. and W. A. Lund, Jr. 1977. A contribution to the life history of the blueback herring, Alosa aestivalis. Trans. Amer. Fish. Soc. 106:533-589. Mansueti, A. J. and J. D. Hardy, Jr. 1967. Development of fishes of the Chesapeake Bay Region. An atlas of egg, larval and juvenile stages. Natural Resources Institute, Univ. Maryland. Marcy, B. C., Jr. 1969. Age determinations from scales of Alosa pseudoharengus (Wilson) and Alosa aestivalis (Mitchill) in Connecticut waters. Trans. Amer. Fish. Soc. 98:622-630. Messieh, S. N. 1977. Population structure and biology of alewives (Alosa pseudoharengus) and blueback herring (A. aestivalis) in the Saint John River, New Brunswick. Env. Biol. Fish. 2:195-210. Miller, R. B. 1946. Notes on the Arctic grayling, Thymallus signifer Richardson, from Great Bear Lake. Copeia:227-236. Netzel, J. and E. Stanek. 1966. Some biological characteristics of blueback, Pomolobus aestivalis (Mitch.), and alewife, Pomolobus pseudoharengus (Wils.), from Georges Bank, July and October, 1964. ICNAF Res. Bull. 3:106-110. Norden, C . R. 19 67. Age, growth, and fecundity of the alewife, Alosa pseudoharengus (Wilson), in Lake Michigan. Trans. Amer. Fish. Soc. 96:387-393. Odell, T . T. 1934. The life history and ecological relationships of the alewife, Pomolobus pseudoharengus (Wilson) in Seneca Lake, New York. Trans. Amer. Fish. Soc. 64:118-126. Pritchard, A. L. 1929. The alewife (Pomolobus pseudoharengus) in Lake Ontario. Univ. Toronto Stud., Biol. Ser. 33, 39:39-54. Ricker, W. E . 19 75. Computation and interpretation of biological statistics of fish populations. Fish. Res. Bd. Canada Bull. No. 191. Rothschild, B. J. 19 63. A critique of the scale method for determining the age of the alewife, Alosa pseudoharengus. Trans. Amer. Fish. Soc. 92:409-413. von Bertalanffy, L . 193 8. A quantitative theory of organic growth. Human Biol. 10:181-213. Watson, J. E. 19 64. Determining the age of young herring from their otoliths. Trans. Amer. Fish. Soc. 93:11-20. Williams, T. and B. C. Bedford. 19 74. The use of otoliths for age determination. Pages 114-123 in T. B. Bagenal, editor. The ageing of fish-proceedings of an international symposium. Unwin Brothers, Old Woking, England. TABLE 1. Mean back-calculated fork length (ram) for blueback herring males as determined \ ~ r • IP l—I -p -P u o g o m o •H ■H i—I ■—i ts si U} Q O ,Q i—i M-l CO - -p 25 cn P g -P u -P PI £ s ss 3 > c c 10 CO 3 o o cu < H cu (U 03 h r- CP r^ p c 1 —1iH 1— 1 CM ^ 00 ■^r VO OCM VO VO i—1 CM 00 CO i—1 ■vf 1—1 00 000 00 00 — 1—1 1—1 CP 00 -sT •H co 00 CP CM CM in MC CM CM CM VO CM n00 CM in MCO CM "VO r" in — rH 1—1 r~' in 1—1 CM CO OH1 H VO rH i—I in nr"-CP in VO CM CM H1—1 rH i—1 CM MVO CM CM vo co H CM CO CM CM CP 1 i—1 rH CM CM 00 1—1 CM KT CM CM CM in CM i—1 CM CM CM o in VO 00 r- 00 1—1 CM CM r-> CO CO CM MC CM CM CM 00 CO in h CM in 00 in o in rH 1—1 nV r- VO in CP MC CM CP CM CM CM CM CM CM r-» o o CO in o o 1 CP 1—1 rH CO i— CO in in CM 00 " CO CO CM in CM in r>* n T l •H 00 nO 1—1 000 00 1—1 CM ■'tfCM CM in in 00 o o H1 CO CM in in CM CP S -p CU cu fd c CU CO rH m c CO rH CM p c rC in vo o H -P -P u o o u £ £ £ cu a) C 39 TABLE 2. Mean back-calculated fork length (ram) for blueback herring females as determined •H h m rH A 4-> -p u 1 o 0 in *H •H iH o n MHW rG d) r— I rH .G a a w U) CJ < -P -P -p £ P 6 0 G G 3 cu CD *H & U o c G O S S £ e^ G fd rd G o in cu fd H X H H u o CD i—I 00 VO 00 VO rH co rH rH CM 00 VO VO VO 00 H CO 00 H1 i— 1 00 VO 1 H 00 I—I LD LT) i—I CM 00 1— 1 MCM CM LT) CT> 00 rH 00 in CM CM CM MCM CM 00 i—1 rH i—1 CM 00 vo VO O I> VO VO CM CM vo CM in LT) CM 00 00 CTi r-> in MCM CM in O i T C m CM CM 00 vo i—l MCM CM i—1 i—l o 00 CM uo CM o OC CM CM CO CM CO CM r—I CTv cn cr> vo o CO i—1 in CM in VO CM r- vo 00 T in CTi CM i CM oo LD CM vo no in - r CM VO o p VO — I - CM H1 CM CM r- i rH CM CM VO CM p* 1 00 CM o VO CT> VO m p- CM TABLE 3. Summary of the age determinations of 34 4 blueback herring. Values indicate the number of specimens having a given age determined by both scale and otolith methods. Italicized values represent those cases in which scale and otolith readings are in agreement. Scale Age 1 2 3 4 5 6 7 8 1 3 2 2 2 1 3 9 2 1 (D tn 4 1 4 5 2 & +J 5 3 5 0 8 3 1 •H iH o 6 4 1 2 5 8 1 -p o 7 2 5 6 6 9 8 5 1 1 6 9 1 42 TABLE 4. Chi square (X2) test of independence of age frequencies based on scale and otolith ageing methods. Age 12345 6 789 Scales 5 2 11 9 62 145 79 27 4 Otoliths 3 5 12 12 65 138 82 23 4 X 2 = 2.88 with 8 df; P>0.9. TABLE 5. Mean back-calculated fork length (mm) for blueback herring males as determined mh —! i— U O £ W O 0 w rd MH W *H rQ U d! n3 d! ■—i ■— i < c/3 52! w S PJ -P -P -p O S -P e 0 cd o d cd 0 NLO CN 00 CD CO CD rH HrH rH CN cn CD CO r- r-' oo cn H r- O CO r- CN o CN O •^r co f"-cn co r- CO CN in CO CN LO in in CO CN i— 1 r" CN CO in co r- co co CO - r CD CN o CN cn CN NCN CN rH «— CN i— CN CO l—l 1— 1 CN CN CN CN i> cn H cn cn cn CO r" CN CN 1 1 t CM LO CN CN CN co ["' CN f"- rH rH cn CN CO cn CO co CD O ninCN in CN -^r CN CN CN in i CN H* CN O cn i CN O cn •'31 CN CD o cn o cn CN — — 1 1 i—I co CN CN CN CO cn in CN CN CN CN oo in X! TJ s -p S 0 r- co co in in r- cn CN d! •P H o -p o u u d 0 £ 0 o £ d 43 TABLE 6. Mean back-calculated fork length (mm) for blueback herring females as determined *4H rH u o B cn o rd o cn -rH ■Q *H rH cn m 2 cn nO I—I A c u UD ■P -P -P e i LO O ro o lo — 1 rH CN LO o LO o i—I co n c 0 0 CO r- n c oo oo r- rH r"-LO CN cn in n c LO rH ■—I CN CN CN 'Sj* in CN CN CN cn o cn O 00 I—I rH CN CN o r CN CN O O CN CO LO oo in I"" CN LO nin in LO co ■<3* rH CN i—1 CO CO i—1 00 CO CN 00 CN in CN m cn 00 CO CO CO cn cn CN LO CN LO CN — i—1 i—I i—1 CN CN CO O i—1 00 CN CN NCN CN I"- I*'*00 r" CN CN CN in LO NCN CN 00 cn 00 CN r- CN CN i—1 CO CN 00 in LO LO LO in 00 O in r> \ T ( CN LO co CN CO oo CN CN LO CN CO 00 CN 00 in oo CN CN in o in in : s 0 * IS -p a (D cn (1) CD fd 0 Cn CN CO CO -^r 00 in r"- CN oo CN CN CN in A o -P H ■p u o 0 U B £ o ) Q CD 0 44 TABLE 7. Comparison of von Bertalanffy lengths-at-age and observed mean lengths for male X Td i—1 P i—1 p P P & fd 0 0 G cd u u g 0 fd O 0 G < CD CTi 00 i—1 CN p-~ OC nin in in CO LO LO ro ■*3* i— S rd 0 i H O rH CO td o cd cn CN i—1 Oi ni *p" p* in in LO in H I"* 00 LO ni ni OLO LO in in in in 00 CN CN ■*3* CN CN P p~ CN CN CN CN CN oo ro i—1i—i CN CN CN CN CN CN P p^ 00 CN CN O CTi nL O LO in P PQ > 0 df dfd fd fd fd g u fd G CN H'sr ^ tH i—i i—I ■o NC NCN CN CN CN X o NC NC CN CN CN CN CN 0P- P- 00 CN i—1 p~ r^> CN CN CN ro in o O U > cn 0 CD •H P i p P o — cn 0 1 N C NC CN CN CN CN CN CN 1—1 1—1 rH r-H rH o r CO in in ro ro LO LO C O'* O CN m in 0 0 00 00 00 P» 00 CN CN LO CN rH P PQ P Td p 0 > O P G cn 0 U fd g CN LO G> 2 7 1 1 1 46 TABLE 9. Mean lengths and weights of blueback herring from Herring Creek for 1977. ^ s w W £ w W £ S £ w rtj rtj rfj S E W W < Q 2 !S W !S I P S I P S w C PI fa !2 C z w z H O K E [2: V) w Ps C w > H O «< s E u O O W H E m o E E E E < l h h h h h h h h J iH rH rH 1 1— 1 1—I -P Q fa s fa £ fa s - n e di— 1 rd 0 td CM 0 to cn 0 stations in Herring Creek. H HERRING CREEK < f t ' . V V J i .« <■« < < ■ ^ ' 49 Figure 2 Beach seine collection sites (JA47, JA90, and JA95) for young-of-the-year blueback herring in the James River. 50 Figure 3. A. Scale from Alosa aestivalis in age group V with one spawning check. B. Scale in age group VI. C. Scale in age group VII with three spawning checks. D. Regenerated scale. Figure 4. A. Otolith from Alosa aestivalis in age group V. B. Otolith in age group VI. C. Otolith in age group VII. D. Partially crystallized otolith. Figure 5. Fork length - scale radius relationship for male and female blueback herring. Dots show the scatter of the data but do not necessarily represent unique data points. Coefficient of determination is r2. FORK LENGTH (mm) 240 200 280 160 120 40 80 0 * • • • / • 50 CL RDU (m ) 0 4 X (mm RADIUS SCALE • • 100 150 • • F L * 20.8 ♦ 0.86R ♦ 20.8 * L F 200 •••• 0.94 •*••** • • • / • •• • • • • 250 • • •• I • • • • / % 'It • 4 «• • •• Is? • • y • ••• • • • • • • 300 53 Figure 6. Fork length - otolith radius relationship for male and female blueback herring. Dots show the scatter of the data but do not necessarily represent unique data points. Coefficient of determination is r2. FORK LENGTH(mm) 200 280 240 160 120 40 80 0 0.4 TLT RDU (mm) RADIUS OTOLITH ••• • • • • • • • • 0.8 • •• • • 1.2 • • * . t* L» 5. 180.05R ♦ -52.8 »FL ■0.94 1.6 : • • : h \ A ' • • * * / 2.0 54 Figure 7. Von Bertalanffy growth curves for male blueback herring derived from scale and otolith back-calculated lengths-at-age. FORK LENGTH (mm) 240- 200 280- 120 160- - 0 4 - 0 8 - - 0 3 G (years) AGE 4 - OTOLITHS - SCALES L,= 263 f-.-0 W 7 (t-0 .0 l6 0 )] )] 0 l6 .0 (t-0 7 W f-.-0 263 L,= .22j-’0-4680"0-3333!!jf-*’ L.-262 5 6 7 9 55 Figure 8 Von Bertalanffy growth curves for female blueback herring derived from scale and otolith back-calculated lengths-at-age. FORK LENGTH (mm) - 0 4 2 0 0 2 280- 120 160- “ 0 4 - 0 8 - - 0 2 3 G (years) AGE 4 OTOLITHS -8 h“*3(-03662); “°*436(t- h .-280 L 5 6 8 9 56 Figure 9. Total weight - fork length (A) and total weight - total length (B) relationships for male and female blueback herring. Coefficient of determination for the linear expression is TOTAL WEIGHT (g) TOTAL WEIGHT (g) 300 200 - 0 5 2 50- 25 300“ 200 150- 100- 150- - 0 5 50“ - - 0 0 TW »(I.670 XIO* )FL33*44 XIO* »(I.670 TW W■(.7 Xl 3*3701 L T ^ lO X TW■ (1.070 2 0.97 *0 r2 2«0.97 r2 50 50 100 100 OA LNT (mm) LENGTH TOTAL O K LENGTHFORK (mm) 5 200 150 5 20 5 300 250 200 150 5 300 250 57 Figure 10. Eviscerated weight - fork length (A) and eviscerated weight - total length (B) relationships for male and female blueback herring. Coefficient of determination for the linear expression is r2. EVISCERATED WEIGHT (g) EVISCERATED WEIGHT (g) 300 200 0- 30 250 250 100 150- 100 0- 50 - 100 0 0 W *(.0 ) )FL K)X EW (3.700 * EW * (2.424 X loT6)EW 2006 (2.424 * TL3 r 2 >0.98 2 r r2 « 0.98 50 50 100 TOTAL LENGTH (mm) LENGTH TOTAL FORK LENGTH(mm) 150 5 20 5 300 250 200 150 9.2044 200 250 300 58 Figure 11. Surface water temperature in Herring Creek during the blueback herring spawning run in 1977 starting March 21 and ending May 13. 59 CO CO in >>to o *o ZD a: 0 z z1 o. C/D so Ba: - o CM GO CM CM CM (D) 3 U m v a 3dW31 U3XVM 30V3UnS VITA Jack Gerald Travelstead Born in Louisville, Kentucky, July 15, 195 4. Graduated from De Sales High School, Louisville in May, 1972. Received B.S. from Old Dominion University, Norfolk, Virginia, May 1976. In September 1976, the author entered the College of William and Mary as a graduate assistant in the Department of Ichthyology. 60