SPECIES SIHILARITY AND HOVE}fENT OF FISH ASSEHBLAGES ON
ARTIFICIAL AND NATURAL REEFS IN HONTEREY BAY, CALIFORNIA
/
A Thesis
Presented to
The Faculty of the Department of Biology
San Jose State University
In Partial Fulfillment
of the Requirements for the Degree
Haster of Arts
Ry
Kathleen Ryan Matthews
December 1983 TABLE OF CONTENTS
Page
LIST OF TABLES iv LIST OF FIGURES v ACKNOWLEDGMENTS vi ABSTRACT .. viii INTRODUCTION 1 MATERIALS AND METHODS 4 / Study Site 4 Underwater Fish Transects 5 Fishing Pressure 7 Fishing Success 7 Tagging Study 8 Sampling Method Comparison 9
RESULTS 10
Underwater Transects 10 Fishing Pressure 14 Fishing Success 15 Tagging Study 16 Sampling Method Comparison 18
DISCUSSION 19 CONCLUSIONS 27 LITERATURE CITED 28 TABLES 30 FIGURES ... 42 APPENDIX 50
iii LIST OF TABLES
No. Page
1 .. Description of the four natural and artifical reefs 31
2 .. Summary of underwater transects for Surfer Reef from fall 1981 through summer 1983 ••••••• 32
3. Summary of underwater transects for Rockfish Reef from fall 1981 through summer 1983 • • • • • 33
4 .. Summary of underwater transects for Tankhouse Rock from fall 1981 through summer 1983 ••••• 34
5. Summary of underwater transects for artificial reef from fall 1981 through summer 1983 • • • • • .. .. • ...... 35
6. Summary of the cumulative totals for all reefs of underwater transect-s from fall 1981 through summer
1983 e o e e • e • e o o e e • • e • e 36 2 7. Estimated mean densities (#/m ) +standard devia tion for all fish observed on underwater transects from fall 1981 through summer 1983 in Soquel Cove on the artificial and natural reefs. Statistical comparison of natural reefs versus artificial reef 37 using single factor ANOVA .. .. " ...... 38 8 .. Sunnnary of tagged fish from natural reefs 0 ...... " 9. Totals of fishes that had moved from tl).e natural reefs to 39 the artificial reef ...... " . " .. " ...... 10. Underwater observations of tagged fish from April 1982 through July .. .. 40 1983 .. . " ...... " .. . " " 11 .. Percent Similarity Index for the two sampling methods - hook-and-line and underwater transects used on the four natural reefs ...... 41
Appendix 1. Size, date tagged, days at liberty, date recaptured, and movement noted for recaptured fishes from all natural reefs . • . • . • . . . 51
iv LIST OF FIGURES
No. Page
1. Map showing location of artificial and natural reefs 43
2. Cumulative number of species for the four transects conducted during the summer of 1982 on the natural and artificial reefs • • • • 44
3. Cumulative species curves for the 3 natural reefs and the artificial reef • • • • • 45
4. PSI values for fall 1981 and summer 1982 for under- water transects •• 46
5. PSI values for cumulative totals from fall 1981 46 through summer 1983 for underwater transects . .. " . ..
6 .. Percentages of rockfishes from the four size cate- gories seen on underwater transects from fall 1981 47 through summer 1983 " ......
7. Mean number of estimated hours + standard error for the natural and artificial reefs from Harch 1981 through July 1983 ••••••• 48
8. Mean number of fish per angler hour + standard deviation for each month from February 1982 through July 1983 on the four natural reefs ...... 49
v ACKNOWLEDG}1ENTS
My committee members, Drs. Greg Cailliet, Mike Foster, and Ralph
Larson were very helpful with their comments, suggestions, and critical review of this thesis. Dr. Robert Lea also provided valuable insight.
I would also like to express my gratitude to Al Solonsky who initiated the work on the artificial reef project. Frank Henry and Jim
Hardwick of the California Department of Fish and Game were also helpful in the logistics of this project.
A very special thanks go to the people who keep Hoss Landing Marine
Lab running: Sheila Baldridge, Signe Johnson, Gail Liragis, Dorothy
Lydick, Sandy O'Neill, Rosie Stelow, and Deborah Tuel. Without their help I surely would have never completed this project.
Larry Jones and Preston Watwood were very helpful in their heroic
attempts to keep the MLML boats in running order. Tracy Thomas and
Alistair Hamilton were instrumental in providrng extended trips on the
R.V. Ricketts. Don Canestro, Barbara Pierson, and Baldo Marinovic kindly helped with the diving.
A special thanks is also extended to Pat Dellin for providing
untiring assistance in the field on the sometimes exciting and sometimes
boring fishing trips. Pat also provided constructive criticism on this
vi study and valuable friendship. Jana Linfield unselfishly prepared many
graphs on the Hewlitt Packard 9825 computer.
Finally, I would like to thank the David and Lucille Packard
Foundation and the American Fishing and Tackle Manufacturers Association
for providing financial assistance.
vii ABSTRACT
A study was conducted to investigate the sequence of interactions between the fish populations on a new artificial reef and those on nearby natural reefs in Monterey Bay. Underwater transects revealed
that the species composition of fishes on the artificial and natural
reefs was similar after one year. Colonization on the artificial reef consisted of adult and subadult rockfishes, surfperches, greenlings, and
cabezon. Monitoring studies demonstrated that a greater amount of
sportfishing occurred on the marked and easily accessible artificial
reef, mostly by skiff fishermen. A fish tagging study revealed that substantial movement of fishes occurred, in some cases up to 1.6 km,
from the natural reefs onto the artificial, but no movement was observed from the artificial reef to the natural reefs. Early colonization by adult and subadult fishes, subsequent substantiated movement from the natural reefs onto the artificial reefs, and large amounts of fishing
pressure suggest that artificial reefs could have detrimental effects on natural reef fish populations. Although it is impossible to know what
proportion of colonizers came from nearby natural reefs, the location of
the natural reefs may be an important consideration when planning the
placement of future artificial reefs.
viii 1
INTRODUCTION
Artificial reefs have been used in fishery management to provide new habitat that will theoretically increase numbers and biomass of depleted fish ·populations, and to mitigate other human activities
(Turner et al. 1969, Buchanon 1974, Walton 1979, Buckley 1982, Grant et al. 1982, Grove 1982). In the state of Washington several artificial reefs have been constructed to improve recreational fisheries by pro viding habitat enhancement that will theoretically increase the number of fishes available to sportfishermen (Buckley 1982). Generally, arti ficial reefs are placed on sandy bottom areas that would originally only support low density fisheries or in areas where populations of fishes have been depleted. The Pendleton Artificial Reef in southern California was built as mitigation to offset any negative effects of the San Onofre
Nuclear Generating Station by enhancing fish and kelp resources (Grove
1982).
Although it is known that artificial reefs attract fishes typical of rocky-reefs, it is not known from where they originate or what the effect is on local fish populations. Colonization by adult and subadult fishes on artificial reefs combined with increased fishing pressure suggests that artificial reefs may not increase biomass or numbers of fishes but merely provide an alternate habitat more accessible to exploitation. It has been repeatedly demonstrated that shallow water
(less than 30 meters) artificial reefs in temperate systems quickly 2
attract an assemblage of adult and subadult reef fishes including
rockfishes, surfperches, and greenlings (Turner et al. 1969, Dewees and
Gotshall 1974, Gascon and Miller 1981). As opposed to invertebrate
colonists, many of which recruit from the plankton, fish colonization
onto artificial reefs in temperate waters generally consists of adult
and subadult recruitment (Gascon and Miller 1981). Gascon and Miller
(1981) rarely saw recently metamorphosed fishes and found no significant
difference in species composition when they established artificial reefs
during different seasons. Also, those artificial reefs that are well
marked and easily acccessible to sportfishermen often receive much
greater amounts of fishing pressure than natural reefs (Turner et al.
1969, Buchanon 1974). Since temperate artificial reefs do attract reef
fishes, this could suggest that fishes are moving from nearby natural
reefs. No studies in temperate systems have attempted to determine the
extent to which fishes inhabiting artificial reefs have moved from
nearby natural reefs. Another source of recruitment onto artificial
reefs may be rocky-reef fishes that have not been able to establish
territories on reefs and are roving about on sandy areas.
The suggestion that rockfishes, surfperches, and greenlings might
move from nearby natural reefs to colonize an artificial reef counters
the current viewpoint that shallow water rockfish exhibit minimal movement (Miller and Geibel 1973, Love 1978, Love 1983). Love (1978)
categorized most shallow water benthic rockfishes as non-movers or those
that move about little (stay on the same reef system). Most conclusions 3
about the amount of movement exhibited by a given species of rockfish come from limited tag return information, sometimes as low as one
(Turner et al. 1969, Miller and Geibel 1973). It is obvious that the movements of rockfishes are poorly understood. Furthermore, although benthic rockfishes and some midwater rockfishes are considered not to move, it has been noted that their numbers do decrease during the winter, so some movement could be taking place (Miller and Geibel 1973,
Moulton 1977). It may be that minimal tag returns in tag recapture studies and problems encountered with sampling during the winter account for the minimal movement noted for rockfishes.
To further understand the effect of artificial reefs on natural reefs, I studied a new artificial reef in Capitola, California to answer the following questions:
1) Is the fish assemblage on the Capitola artificial reef similar
to those of nearby natural reefs, and does this similarity
change over time?
2) How does the amount of fishing pressure compare on the natural
and artificial reefs?
3) How do the fishing success rates compare between the artifi
cial and natural reefs?
4) How much movement of fishes occurs between the natural and
artificial reefs and does this amount of movement change over
time? 4
MATERIALS AND METHODS
The Capitola artificial reef, constructed in August of 1981, is
located 1.3 km south of the Capitola Pier (Figure 1) at latitude
36°56.7'N, longitude 121°57.3'W. At the time of construction, two
artificial reefs were established in Soquel Cove, one marked and one un
~arked, but this investigation only involved the marked artificial reef
(see Solonsky 1983)o The reef lies in 13g7 m of water on sand-covered mudstone, and is marked with a 3 m orange buoy designating it as an
artificial reef. The reef consists of 240 concrete pipes, and covers an 2 area of 1200 m • The pipes have inside diameters ranging from 30-250 em while the vertical relief ranges from 0.5 to 5 m. The artificial reef
is located in Soquel Cove, where the water is generally very turbid, bottom visibility generally being less than 2 m. The artificial reef
has no large algae growing on it at this time and as light is low it is very unlikely that any will grow.
Study Site
Four natural reefs in the immediate area were investigated (Figure
1). Two of these reefs, Surfer and Rockfish, are 0.8 and 1.2 km south- west of the artificial reef (Table 1). Surfer Reef is 12.2 m deep, sur- rounded by sand, and supports a perennial stand of the giant kelp, Macro- cystis pyrifera. Rockfish Reef is 15 .• 2 m deep and is also surrounded by
sand, but has no giant kelp. Both of these reefs consist of flat rock with some ledges and vertical areas that rise to 3 m off the bottom. 5
2 reef covers approximately 5000 m • The third reef, Adams Reef, has
area and ranges from 0.8-1.6 km south of the artificial reef.
It consists of flat rocks interspersed with sand and covers approximate- 2 200.000 m • The bottom depth ranges from 21-..3-27 .. 4 m, with little vertical relief (0-1.5 m). Like the artificial reef, Adams has no giant kelp. The fourth natural reef, Tankhouse Rock, is 0.8 km north of the artificial reef and supports a lush stand of kelp. Tankhouse is approxi- . 2 mately 4000 m , 10.7 m deep, and has little vertical relief (0-1 m).
During the winter storms of 1982-1983 most of the kelp in Monterey Bay was removed and the canopy at Surfer Reef has not yet grown back.
Tankhouse also lost most of its canopy but most grew back during the summer of 1983.
All sampling was conducted from the fall of 1981 through the summer of 1983. The winter storms of 1982-1983 precluded sampling during the months December 1982 through April 1983.
Underwater Fish Transects
Underwater transects were used to estimate the abundances, size frequencies, and species composition of fishes inhabiting the natural and artificial reefs. Permanent 30.5 m (100 ft) transects were placed on each reef. At least four 15.2 transects were attempted each quarter for each natural and artificial reef surveyed, although visibility or weather sometimes made this impossible. Starting in the middle of the permanent 30.5 transect line, the divers would swim a 15.2 m transect in 6
one direction and then one in the other direction. Water column fishes
(up to 2 m off the bottom) were counted in the first 15.2 m swim and benthic fishes on the return swim. Each of the two divers counted the fishes 1 m on one side of the transect line. Fishes were identified to species, counted, and placed into one of four size categories (<6 em,
6-12 em, 12-20 em, or )20 em) with a centimeter rule on the underwater / clipboard as ·reference. Data were recorded on prelabeled underwater paper held onto a clipboard. All species encountered were recorded.
Due to depth and time constraints, underwater transects were not con- ducted on Adams Reef.
Cumulative species curves were drawn to test whether adequate species sampling had been accomplished over the period of the study.
One season was chosen - the summer of 1982 - to plot cumulative species against transect number since this season had the most species and would require the largest number of samples. Also, Percent Similarity Indices
(Silver 1975) were computed to compare similarities among transects during the summer season 1982 for Tankhouse Rock as transect number did not level.off. PSI's were also utilized to compare species composition on the natural and artificial reefs. PSI values were computed for the first quarter - the fall of 1981, the summer quarter of 1982, and again with the total cumulative percentages at the conclusion of the study, summer 1983.
After each underwater transect the numbers of fishes observed 2 2 per 30.4 m were converted to #/m • Then for each season the mean 7
ishes/m2 + standard deviation was computed from the sum of these
estimates. A single factor analysis of variance (Zar 1974) was
to determine if significant differences existed between mean den
estimates from the natural and artificial reefs.
Fishing Pressure
To determine relative amounts of sportfishing, fishing pressure was
estimated by randomly sampling the amount of sportfishing on weekdays
and weekends (Wine 1978). Our observations were conducted by boat or
from shore and the number of anglers was recorded for each boat present.
The average number of weekday hours of angling was multiplied by 20 (#
of weekdays in a month) for a weekday average and the average number of
weekend hours was multiplied by 8 for a weekend average to result in a
monthly estimate of sportfishing pressure. For example, if randomly
sampling on 3 weekdays estimated average number of 10 angler hours per
day, then the weekday average for the month would be 10 hours x 20 200
hours. If 2 days were sampled on weekend days with an average of 50
angler hours per day, then a weekend total of ~ngler hours for the month would be 50 hours x 8 = 400 hours. Thus, the estimated number of angler hours for that month would be 600 hours. The standard error for these weekday and weekend samples was computed using a stratified sampling
technique of proportional allocations (Snedecor and Cochran 1967).
Graphs of the estimated hours of fishing pressure + standard deviations for 1982-1983 were constructed for each reef. 8
Fishing Success
To determine relative fishing success on each reef, we fished each
reef and computed our monthly mean catch per angler hour + standard
deviation. Research personnel used rockfish jigs baited with squid, and
an effort was made to sample all the reefs an equal number of hours.
/Fishing success was recorded as the number of fish per angler hour.. For
example, if 2 fishermen fished 3 hours on Adams Reef then the number of
angler hours expended that day would be 6 hours. If the fishermen
caught 12 fish during that time period then the number of fish/angler
hour = 2. Adding other sampling periods for that same month would
result in a mean number of fish per. angler hour + standard deviation.
Monthly means of the number of fish/angler hour + standard deviation
were plotted for each reef.
Tagging Study
A fish tagging study was done to determine if movement occurred
between the natural and artificial reefs. Fish were tagged with Floy
spaghetti tags that were numbered and color coded for each reef.
Subsequent monitoring of the sportfish catch, our hook-and-line fishing,
and underwater observations provided tag recapture data. All fishes
were caught using hook-and-line and were identified, measured (em TL),
and a tag inserted on the anterior-dorsal musculature. Only fishes
tagged on the natural reefs will be reported in this study (see Solonsky
1983 for information on fishes tagged on the artificial reef). Each tag
was marked with the following information: "REWARD MLML 408-633-3304 9
Tell size and where caught". The fish tagging project was well adver tised using flyers and posters displayed in local bait and tackle shops, the Capitola wharf, and the Santa Cruz boat launching ramp starting in
March of 1982. We also distributed flyers to most boats being launched from the Capitola wharf and any fishermen that were encountered during our work in Soquel Cove. To alleviate swim bladder problems in some individuals, we used a syringe to deflate the swimbladder (Gotshall
1964). If fishes were seriously damaged during capture they were not tagged.
Sampling Method Comparison
To compare the species composition of the two sampling methods, hook-and-line and underwater transects, a PSI was computed. Percentages of all fish species caught by research personnel by hook-and-line were compared to percentages of all species seen on underwater transects throughout the study period. 10
RESULTS
Underwater Transects
The cumulative species curves for the four transects performed during the summer of 1982 levelled after 3 to 4 transects (Figure 2).
Four transects per season appeared to be adequate to describe the spe-
assemblage on each of the reefs. The species numbers on Rockfish and Surfer Reefs levelled after 3 transects. Although additional tran sects at Tankhouse Rock did add 4 more species, these were rare species amounting to less than 1% of the total number of individuals observed on the underwater transects. The species sampled on different transects at
Tankhouse Rock were similar (PSI between 0.84 - 0.93) indicating the dom inant species were present and in similar abundances on all transects.
The species numbers on the artificial reef also levelled after 3 to 4 transects.
The species composition became consistent after 4 to 5 seasons on all 4 reefs (Figure 3). The cumulative species curves over the entire sampling period plateaued after four season. After the spring of 1982 only rare species were added to the species pool on all reefs (Tables
2-5). For example, during the summer of 1982 three more species were observed on Rockfish Reef, the vermilion rockfish, Sebastes miniatus, the canary rockfish, S. Pinniger, and the pile perch, Damalichthys vacca
(Table 3). These three species only accounted for 4% of the total num ber of individuals observed during the summer and are occasional visitors. 11
Surfer reef had the greatest number of recorded species (23) and was dominated by the blue rockfish, Sebastes mystinus (41%) and the olive rockfish,~· serranoides (26%) (Table 2). The blue and olive rockfish were present all seasons sampled. The greatest number of species were present during the winter 1981-1982 (15) and the fall of
1982 (13). The greater number of species present was generally attrib uted to the occasional appearances of a few individuals of the pile perch, the rubberlip surfperch, Rhacochilus toxotes, the vermilion rockfish and the cabezon, Scorpaenichthys marmoratus all of which accounted for only 5% of total numbers of individuals observed.
Twenty species were observed on Rockfish Reef dominated by the blue rockfish (49%) and the olive rockfish (37%) (Table 3). The greatest number of species (14) was observed during the summer of 1982 while the lowest numbers occurred during the fall of 1982 (9) and the spring and summer of 1983 (10). Again, the increased numbers of species observed during the summer of 1982 w~re due to the occasional appearances of the vermilion rockfish, the pile perch, the rubberliP. surfperch, and the striped surfperch, Embiotica lateralis and these species only amounted to 3% of the total of individuals observed.
Tankhouse Rock also had twenty species but was dominated by three species, the white surfperch, Phanerodon furcatus (39%), the blue rockfish (26%), and the olive rockfish (20%) (Table 4). This reef had 12
the highest numbers of the white surfperch and was the only reef with the grass rockfish, Sebastes rastrelliger. Greatest numbers of species were observed during the summer (18) and fall (15) of 1982 while the lowest occurred during the winter (7) and spring (8) of 1982. These high species numbers were due to the presence of the rubberlip perch, the shiner surfperch, Cymatogaster aggregata, the striped surfperch, and the vermilion· rockfish all of which comprised less than 3% of total numbers of individuals observed.
The marked artificial reef had 21 species and was dominated by three species, the blue rockfish (32%), the olive rockfish (21%), and the white surfperch (16%) (Table 5). The seasons with the greatest numbers of species were the summer of 1982 (16), spring of 1983 (16), and summer of 1983 (16). The lowest numbers of species were observed during the fall of 1981 (7) and the spring of 1982 (7). Again, the higher numbers of species observed during the spring and summer were due to the occasional presence of the vermilion rockfjsh, canary rockfish, shiner surfperch, and the striped surfperch.
A total of twenty-five species was observed between 1981 and 1983 on all natural reefs (Table 6). The three dominant species, the blue rockfish (38%), olive rockfish (28%), and white surfperch (15%) comprised 81% of the fish seen on the underwater transects. After combining all natural reefs it is evident that the occasional visitors comprised a negligible portion of numbers observed. The brown rockfish, 13
• auriculatus, gopher rockfish,~· carnatus, and black-and-yellow rockfish, ~- chrysomelas only comprised 3% of total numbers observed on all natural -reefs ..
The species composition was fairly similar among the natural reefs both during the summer of 1982 and when total numbers from all seasons were compared (Figure 4). Low PSI values were noted during the fall of
1981 when only two transects per reef were performed indicating this was an inadequate number of transects. During the summer of 1982 the PSI among natural reefs ranged from 0.61-0.70 with Rockfish and Tankhouse
Reefs being the most similar. Tankhouse rock was the only natural reef with a large percentage of white surfperch (39%) which accounts for the
PSI not being higher among natural reefs. When all transects were totalled at the end of the study (summer 1983) the PSI ranged from
0.53-0.79. The highest degree of similarity existed when comparing
Rockfish and Surfer (0.79).
By the summer of 1982 the species composition of the artificial and natural reefs was similar (Figure 5). Relatively high PSI values of
0.71 and 0.74 occurred when comparing the natural reefs combined to the artificial reef.. The PSI values were quite low in the fall of 1981 because the artificial reef had been in the water only a few months, and only two transects were made that quarter.
While species composition on the artificial reef was similar to the natural reefs, four species of fish that were inhabitants of the natural 14
never seen there. The kelp surfperch, Brachyistius frenatus,
, Oxyjulis californica, china rockfish, ~· nebulosus, and grass
, ~· rastrelliger were never seen on the artificial reef. The
surfperch and senorita were also not seen on Rockfish Reef and,
the artificial reef, it supports no kelp.
Only adult and subadult rockfish )6 em inhabited the artificial reef for the first three seasons after it was established (Figure 6).
Small (<6 em) rockfish were observed on all natural reefs all seasons except the winter of 1981 and the spring and summer of 1983. Very few small rockfish were observed during the summer of 1983 after the winter storms destroyed the kelp canopy.
The artificial reef had significantly higher mean density estimates
(Single factor ANOVA) than any natural reef for six of the eight seasons studied (Table 7). Significant differences resulted when comparing densities on the artificial reef to all natural reefs from the cumula tive totals for 1981-1983. There were no significant differences between mean density estimates for the cumulative totals among the natural reefs.
Fishing Pressure
Sportfishing underwent seasonal changes, with the highest estimates during the spring and summer. No fishing was observed from November
1982 - April 1983 due to both the seasonal nature of fishing and the severe storms. Although it was sometimes impossible to sample at sea 15
the winter storms, we could still sample from shore. Sport-
on the artificial reef did not begin until March of 1982, after
had been publicized and the Capitola wharf started renting
The marked artificial reef received the greatest amount of monthly
pressure during the 1982-1983 study period (Figure 7). During
the month of May 1982 the estimated fishing pressure on the artificial
reef was at least 4 times higher than on any natural reef. During the months of May, June, and July of 1983 the estimated fishing pressure on
the artificial reef was 3-16 times higher than any natural reef.
As the artificial reef was the easiest reef to locate (well marked with a buoy) and did not require a depthfinder, most small skiffs were found fishing around the buoy. Adams Reef, the natural reef with the greatest amount of fishing pressure, was the largest of all the reefs studied and would oftentimes be found with larger, fathometer-equipped boats. Surfer and Rockfish Reefs were difficult to locate without a fathometer.
Fishing Success
Fishing success was highly variable not only from month to month but within months (Figure 8). Fishing success often varied from hour to hour, with 20 fish being caught one hour and 9 the next. The highest
CPUE values were recorded during the summer and fall, and the natural reefs generally yielded more fish per angler hour than the artificial 16
(see Solonsky 1983). Of course, due to the variable nature of
these fishing success estimates no significant differences can be cited.
Tagging Study
Two hundred sixty-two rockfish of eleven species, eight lingcod,
and two kelp greenling were tagged from 1982-1983 on the four natural
/reefs (Table 8)! Of the 272 fish tagged, 86% were of four species:
blue rockfish, gopher rockfish, brown rockfish, and black-and-yellow
rockfish. Thirty-nine fish were recaptured (14.3%) and of these 87.2%
were recaptured by sportfishermen and 12.8% recaptured by our own
fishing effort. The black-and-yellow rockfish and brown rockfish had
the highest recapture percentages (31.3% and 26.2%, respectively).
Thirty-one fish were tagged on Tankhouse Rock with three recaptures
(9.7%). The blue, gopher, and brown rockfish comprised 74.2% of those
tagged. A total of 66 fish were tagged at Rockfish Reef with only 5
(7.6%) recaptured to this date. Fifty-eight of the fish were tagged in
May of 1983 so this may account for the low returns. The gopher, blue,
brown, and black-and-yellow rockfish made up 92.4% of the fish tagged
and 100% of those recaptured. Eighty-eight fish were tagged on Surfer
Reef with 19 (21.6%) recaptured. The blue, brown, and black-and-yellow rockfish comprised 74% of those tagged and 63% of those recaptured. On
Adams Reef 83 fish were tagged with three species, the blue, brown, and gopher rockfish comprising the majority (88%) and 92% of those recap tured. 17
the 39 fish recaptured, 31 (79.5%) had moved from the natural
to the artificial reef (Table 9 +Appendix 1). All three of the
fish from Tankhouse Rock eventually moved to the artificial
where they were later caught. Three of the five recaptured fish
tagged on Rockfish Reef were caught on the artificial reef.
the 19 recaptured fish tagged on Surfer Reef, 15 (78.9%) had moved to
artificial reef. Of the fish recaptured after being tagged on Adams
Reef, 83.3% had moved to the artificial reef. Only six (blue, brown,
, black-and-yellow, and vermilion rockfish and the kelp greenling) of the thirteen species of fish tagged had moved from the natural reefs to the artificial reef. Three fish tagged on Adams and Rockfish Reefs in May of 1983, one blue and two brown rockfish, were recaptured in July of 1983 on the artificial reef, demonstrating that movement is still taking place almost two years after the installation of the artificial reef.
Eight of the 39 (20.5%) fish recaptured were caught on the same reef where they were tagged, indicating that some fish stay on the same reef. After 200 days several fish were recaptured on the natural reefs where they were tagged)~fter-200 Gs¥5 confirming that some fish are quite sedentary (Appendix 1).
Forty-six tagged fish were sighted in underwater observations on natural reefs, and all but 1 of these fish had not moved (Table 10).
Only 1 of these 46 fish had moved from one natural reef to another, a 18
tagged on Rockfish Reef that was seen on Surfer Reef. It
to know how many different individuals were involved in
observations, as the.numbers were impossible to read on the
No fish tagged on the artificial reef (see Solonsky 1983) were
on the natural reefs during underwater observations.
Sampling Method Comparison
The two sampling methods, hook-and-line and underwater transects, were not very similar in assessing species composition (PSI = .50)
11). Only thirteen species were caught using hook-and-line while
species were observed underwater. The gopher rockfish, brown rock-
' and black-and-yellow rockfish comprised 40% of the fish caught on hook-and-line while the same fish only accounted for 3% of the fish seen on underwater transects. 19
DISCUSSION
As expected from other artificial reef studies (Turner et al. 1969,
Dewees and Gotshall 1974, Gascon and Miller 1981), the assemblage of fishes that developed on the Capitola artificial reef was very similar to a rocky-reef assemblage after one year. The highest species similar ity between the artificial and natural reefs existed when comparing the artificial to the combination of all natural reefs studied, suggesting that the artificial reef was a mixture of the fish assemblages from the natural reefs. The similarity between the artificial and natural reefs became greater over time as more species common to the natural reefs recruited on to the artificial reef. Within three seasons after the installation of the artificial reef its species composition was very similar to the local natural reefs suggesting that movement from the local reefs had taken place. There were no species inhabiting the artificial reef that were not seen on the local natural reefs.
The Capitola artificial reef supported th~ highest fish density of any reef studied, in some cases up to 3 times the numbers observed on the natural reefs. This is in agreement with numerous other artificial reef studies (Turner et al. 1969, Walton 1979). Walton (1979) found artificial reefs in Puget Sound to support densities 16 times that found on the natural reefs. The reason why artificial reefs generally support such high densities of fishes is not fully understood, but is thought to be related to the vertical relief offered by the artificial habitats. 20
and Ogren (1981) suggested that artificial reefs provide more
holes, and thus attract large numbers of fishes. Whatever the
artificial reefs do generally support denser populations of
natural reefs.
Capitola artificial reef was initially colonized by adult and
fishes, which appears to be a characteristic of temperate artificial reefs (Gascon and Miller 1981). Thus, for the first three seasons after the artificial reef was established and open to sport fishing, adult and subadult fishes were moving from some other location, either natural reefs or sandy areas, t~ inhabit the artificial reef. As a result, at least the initial recruitment onto the artificial reef is not creating new biomass but moving the biomass from one location to another.
The four species from local natural reefs that did not appear on the artificial reef are thought to be restricted to reefs with kelp or to different depths. So, although a rocky-reef ·assemblage is attracted, some fishes appear to require kelp or a p~rticular depth that the arti ficial reef did not offer. The kelp surfperch and the senorita have been reported to exclusively inhabit the kelp canopy and adjacent reef areas (Bray and Ebeling 1975). Although less is known about the grass rockfish, it is thought to be restricted to shallow water less than 12 meters (Miller et al. 1967). Only two china rockfish were seen on natural reefs and it is possible that one or two were present on the 21
artificial reef and escaped our notice because they are fairly rare and solitary (R. Lea, personal communication).
The kelp rockfish was only observed once on the artificial reef, when 20 juveniles floated in with some drift kelp. They were never again seen after the kelp broke free. The kelp rockfish is thought to be restricted to kelp bed areas (Van Dykhuizen 1983).
Marked artificial reefs receive greater amounts of fishing pressure than most natural reefs (Turner et al. 1969, Buchanon 1974). This was also true on the reef systems of Soquel Cove. Artificial reefs are generally designed for small skiff fishermen to make fishing grounds more accessible. Marking an artificial reef enables the fishing party to find the reef without a fathometer, and is therefore appealing to low-income sportfishermen. Several of the natural reefs were very difficult to locate without a fathometer, and it is likely that they would have received more fishing pressure had they been so marked.
Due to the variable nature of hook-and-line sampling, no analysis could be made of the fishing success data. It was hoped that changes in success rates could be related to changes in population sizes or that some reefs could be sampled by hook-and-line to study their species composition without underwater transects. Regarding the latter, hook-and-line sampling is very species-selective and is inadequate for characterizing actual species composition. Twenty-five species of fishes were observed on underwater transects, while only thirteen were 22
caught using hook-and-line. Also, the brown rockfish, gopher rockfish,
and black-and-yellow rockfish were caught in much higher proportions
than observed on underwater transects. It is likely that their agress-.
ive and territorial behavior makes them easier to catch. Hook-and-line
was also ineffective for population estimates, as on several occasions
qook-and-line sampling would be conducted after underwater fish observa
tions reported very dense groups of fishes and no fish would be caught.
Also, our fish finder would often show large numbers of fishes but our
catch would be minimal. Hook-and-line sampling was effective in this
study for tagging fishes but should not be used for population estimates
or diversity studies.
At least 11.4% of the fishes tagged on nearby natural reefs eventu
ally moved to the artificial reef, where they were caught. Fish were
tagged between February 1982 and July 1983, and thus the study was not
initiated until months after the artificial reef had.been established.
The movement was substantiated by tag returns from May of 1982 through
July of 1983. It is likely that initial colonization also involved move ment of fishes from local natural reefs although we did not tag prior to
the installation of the new artificial reef. Of course, there is no way of knowing what percentage of the fishes recruiting to the artificial
reef came from nearby natural reefs but they are at least one source of recruitment.
If one assumes that 11.4% of the total population of fishes from
the natural reefs moved to the artificial reef and using population esti- 23
mates of these reefs from underwater transects, these migrants could rep
resent 48.9% of the artificial reef fish population. This was estimated
multiplying the are.a of each reef by the density estimates obtained
from the underwater transects resulting in a population estimate for
each reef. Population estimates for Surfer, Rockfish, Tankhouse, and
the artificial reef, using this approach, are 9350, 9050, 8960, and 6372
respectively. If we take 11.4% of the total population estimate of all
the natural reefs (27360), we get 3119. This 3119 would thus represent
48.9% of the 6372 fish estimated for the artificial reef.. So, it appears
that just these three local natural reefs are a major source of recruit
ment to the artificial reef.
I found movement of tagged fish only from the natural reefs to the
artificial reef. Fish tagged on the artificial reef for an associated
study (Solonsky 1983) were neither seen in our underwater observations
on-the natural reefs nor recaptured away from the artificial reef.
Sixty-four fishes were tagged on the marked reef and 17% recaptured with
no movement exhibited. Thus, it appears that once fishes move to the ar-
tificial reef they stay there (or until they are caught anglers) ..
Although there was less fishing pressure on the natural reefs, tagged
fishes from the artificial reef would have been observed on underwater
transects if there had been substantial movement. We saw fish tagged on natural reefs in our underwater observations on the artificial reef.
Tag returns reported movements of up to 1.6 km for the gopher rockfish, black-and-yellow rockfish, vermilion rockfish and brown 24
rockfish. These species are thought to be sedentary (Miller and Geibel
1973, Hallacher 1977, Love 1978, Larson 1980). Since sizes for these fishes ranged from 19-35 em, even the larger (older) individuals had moved. It is not known if the fishes exhibiting movement were ones that lived on natural reefs but were without a territory (floaters). Larson
(1980) reported such floaters in both black-and-yellow and gopher rock fishes, but the floaters were almost always small fish. It is not known if the fish in this study moved for better food, space, or quality of habitat. Regardless of the reasons for movement, at least some of the fishes thought to be sedentary do move up to 1.6 km. Since several studies have reported lower fish densities in the winter, fishes may be leaving the reefs to escape heavy surge, to find food, or perhaps to spawn. It is not known what percentages of these fishes come back to the same reefs or will set up a new residence after stumbling upon a new habitat. The artificial reef was established in August, and within weeks adult and subadult rockfishes had already moved onto the habitat·.
Thus, at least some rockfishes are out moving about even in non-winter periods, perhaps looking for a more desirable habitat. Artificial reefs are generally established in areas of sand or low-relief rocky reefs that need an increased fishery, and this may account for fishes moving to the higher relief an artificial reef has to offer.
Movement occurred from natural reefs, with lower fishing presure, to an artificial reef with substantially higher fishing pressure. Thus, if an artificial reef is marked and open to sportfishing the fishes mov- 25
ing from the natural reefs are more likely to be caught by sportfisher men. This would mean that the fish in the vicinity of the Capitola artificial reef are now more likely to be .exploited if they move to the artificial reef. The fishery management implications of this are obvious: artificial reefs could lead to increased exploitation of local fish populations. Furthermore, if some of the fishes moving to the artificial reef were "rovers" then they came from areas with virtually no fishing pressure. Thus, it is highly likely that no matter where the fishes :recruiting to the artificial reef come from, natural reefs or sandy areas, they are moving to a location with increased fishing pres sure. When heavy fishing pressure occurs on the artificial reef, even more space would be opened for new recruits from natural reefs and again increase their chances of exploitation. Buchanon (1974) stated that the
South Carolina artificial reef he studied could only support the heavy amount of sportfishing it was receiving if recruitment of catchable size fishes from the natural reefs was rapid and continuous.
It is possible that the Capitola artificial reef had more local movement of fishes because it is unique in some way and that such local movements of fishes may not occur in other locations. The close proxim ity of the relatively low relief rocky reefs may account for the high degree of movement observed. Also, many studies dealing with movements of rockfishes have been at the Channel Islands or at locations in
Monterey Bay with high relief reefs, good water visibility and plentiful food (Miller and Geibel 1973, Hallacher 1977, Larson 1980, Love 1978). 26
The fish inhabiting these reefs may be less likely to move away from good conditions.
The attraction that artificial reefs have for fishes from local natural reefs could be useful in fishery management. For example, artificial reefs could be established to attract fishes from local reefs and then utilize the artificial reef as a reserve. The Edmunds arti ficial reef in Puget Sound is protected from sportfishing and maintains a large population of fishes with no danger of exploitation.
It is important in future planning of artificial reefs to take into consideration the location and proximity of nearby natural reefs. Locat ing an artificial reef too close to natural reefs may deplete them in the long run. It is obvious that care and more knowledge of the local area are important in the future planning of artificial reefs. And since artificial reefs may be putting increased pressure on local fish populations, it may be necessary not to use them for _the reason of in creasing the quality of sportfishing unless better management schemes are developed. It may be counterproductive in the long run if artifi cial reefs are actually exploiting more fish. It also may be necessary to take a close look at the cost effectiveness of artificial reefs and see what percentage of the fishing population actually uses them. 27
CONCLUSIONS
1. The Capitola artificial reef was found to attract a rocky-reef
assemblage of subadult and adult fishes similar to those on nearby
natural reefs.
2. The artificial reef received substantially higher amounts of
fishing pressure than the nearby natural reefs.
3. Fish moved from nearby natural reefs, with relatively low fishinf
pressure, onto the artificial reef, with higher fishing pressure
4. As colonization was by adults and subadults, fishing pressure was
high~ and movement of local fishes was substantial, the artifici~
reef could be viewed as detrimental to the local fish population
5. Recommendations were made to use artificial reefs as fishery re
serves and possibly not place them so close to natural reefs.
may be necessary not to think of artificial reefs as increasing
biomass but merely moving biomass. 28
LITERATURE CITED
Bray, R. N. and A. W. Ebeling. 1975. Food, activity, and habit of three "picker-type" microcarnivorous fishes in the kelp forests off Santa Barbara, Calif. Fish. Bull, U.S. 73:815-829.
Buchanon, C. C. 1974. Comparative study of the sport.fishery over artificial and natural habitats off Murrells Inlet. Sea Grant Publication. TAMU- SG- 74- 103. pp 34-58.
Buckley, R. M. 1982. Marine Habitat Enhancement and Urban Recreational Fishing in Washington. Mar. Fish. Rev. 44(6-7): pp. 28-37.
Dewees, C. M. and D. W. Gotshall. 1974. An experimental artificial reef in Humboldt Bay, California. Calif. Fish. Game, 60(3): 109-127.
Gascoe~ D. and R. A. Miller. 1981. Colonization by nearshore fish on small artificial reefs in Barkley Sound, British Columbia. Can. J. Zool. 59(9): 1635-1696.
Gotshall, D. W. 1964. Increasing tagged rockfish (Genus Sebastodes) survival by deflating the swim bladder. Calif. Fish. Game 50: 253-260.
Grant, J. G., K. C. Wilson, A. Grover, and H. A. Togstad. 1982. Early development of Pendleton artificial reef. Mar. Fish. Review 44(6-7): 53-60.
Grove, R. S. 1982. Artificial reefs as resource management option for siting coastal power stations in southern California. Mar. Fish. Rev. 44(6-7): pp. 24-27.
Hallacher, L. E. 1977. Patterns of space and food use by inshore rockfishes (Scorpaenidae: Sebastes) of Carmel Bay, California. Ph.d. Thesis. University of California, Berkeley. 114 p.
Larson, R. J. 1980. Territorial behavior of the black and yellow rockfish and gopher rockfish (Scorpaenidae, Sebastes). Mar. Biol. 58, 111-122.
Laufle, J. C. 1982. Biological development and materials comparisons on a Puget Sound artificial reef. Wash. Dept. Fish. Tech. Rep. 72, 183 p.
Love, M. S. 1983. Movements of Rockfishes. In F. Henry, editor. Proceedings of the 1983 Western Groundfish Workshop, Asilomar Conference Center, Pacific Grove, California. 29
Miller, D. J. M. W. Odemar, and D. W. Gotshall. 1967. Life history and catch analysis of the blue rockfish (Sebastodes mystinus) off central California, 1961-1965. }~0 Reference No. 67-14. 130 p.
Miller, D. J. and J. J. Geibel. 1973. Summary of blue rockfish and lingcod life histories; a reef ecology study; and giant kelp, Macrocystis pyrifera, experiments in }fonterey Bay, California. Calif. Dept. Fish Game, Fish. Bull. 158. 137 p.
Moulton, L. L. 1977. An ecological analysis of fishes inhabiting the rocky nearshore regions of northern Puget Sound, Washington. Ph.D. Dissertation. University of Washington, Seattle. 181 p.
Silver, M. W. 1975. The habitat of Salpa fusiformis in the California Current as defined by indicator assemblages. Limnol. and Oceanogr. 20(2):230-237.
Snedecor, G. W. and W. G. Cochran. 1967. Statistical tfethods, 6th Ed. Iowa State University Press, Arnes, Iowa. 593 p.
Solonsky, A. C. 1983. Fish colonization and the effect of fishing activities on two artificial reefs in Monterey Bay, California. M.S. Thesis. San Francisco State University. 55 p.
Steimle, F. W. Jr. and L. Ogren. 1982. Food of fish collected on artificial reefs in the New York Bight and off Charleston, South Carolina. Mar. Fish. Rev. 44(6-7):49-52.
Stone, R. B., H. L. Pratt, R. 0. Parker Jr., and G. E. Davis. 1979. A comparison of fis4 populations on an artificial and natural reef in the Florida Keys. Mar. Fish. Rev. 4l(a):1-11.
Turner, C. H., E. E. Ebert, and R. R. Given. 1969. Man-made reef ecology. Calif. Dept. Fish and Game, Fish. Bull. 146. 222 p.
Van Dykhuizen, G. D. 1983. Activity patterns and feeding chronology of the kelp rockfish, Sebastes atrovirens in a central California kelp forest. M.S. Thesis. San Jose State University. 53 p.
Walton, J. M. 1979. Puget Sound artificial reef study. Wash. Dept. Fish. Tech. Rep. 50. 130 p.
Wine, V. 1978. Southern California Independent Sport Fishing Survey Annual Report #2. Administrative Report No. 78-2. California Dept. of Fish and Game. 79 p.
Zar, J. H. 1974. Biostatistic Analysis. Prentice-Hall, Inc., Engle wood Cliffs, N.J., 620 p. 30
TABLES Table 1 .. Description of the four natural and artificial reefs.
Vertical Distance from relief artificial reef Depth (m) (km) and direction (m) Kelp Area (m)2
Surfer reef 0-3 0.8 sw 12.2 Yes 5,000
Rockfish reef 0-3 1 .. 2 sw 15 .. 2 No 5,000
Adams Reef 0-1 .. 5 0.8-1 .. 6 s 24 .. 4-30.5 No 200,000 w Tankhouse Rock 0-1 0 .. 8 N 10 .. 7 Yes 4,000 1-'
Artificial reef 0-5 13 .. 7 No 1,200 Table 2 .. Summary of underwater transects for Surfer Reef from fall ~981 through summer 1983. Numbers for each species represent total seen per quarter ..
Fall Winter Spring Summer Fall Spring Summer Total Species 1981 81-82 1982 1982 1982 1983 1983 n = %
Sebastes mystinus 48 41 69 113 151 68 112 602 41 Sebastes serranoides 38 35 58 74 87 48 47 387 26 Phanerodon furcatus 0 18 0 29 12 0 0 59 4 Brachyistius frenatus 5 0 41 14 13 0 0 73 5 Hypsurus caryi 0 0 28 28 18 0 0 '74 5 Sebastes atrovirens 5 0 0 105 0 0 0 110 7 Embiotoca jacksoni 3 0 0 2 4 0 5 14 1 Ophiodon elongatus 4 6 3 1 1 6 4 25 2 Hexagrammos decagrammus 2 4 2 1 1 0 0 10 1 Sebastes melanops 0 7 0 1 2 0 0 10 1 Hyperprosopon argenteum 0 8 0 0 0 0 0 8 1 Oxyjulis californica 0 12 0 0 0 0 0 12 1 w Sebastes auriculatus 3 5 0 0 3 0 0 11 1 N Sebastes chrysomelas 3 4 2 0 3 3 4 19 1 Sebastes caurinus 0 0 1 0 0 0 0 1 Sebastes miniatus 0 0 0 2 1 3 6 12 1 Damalichthys vacca 0 4 0 0 0 0 0 4 Rhacochilus toxotes 0 2 0 0 0 0 0 2 Sebastes pinniger 0 0 0 2 0 1 3 f) Embiotica lateralis 3 0 0 0 0 0 0 3 Cymatogaster aggregata 0 0 0 0 0 0 0 0 0 Scorpaenichthys marmoratus 1 2 0 0 0 0 0 3 Sebastes nebulosus 0 0 0 0 0 1 1 2 Sebastes rastrelliger 0 0 0 0 0 0 0 0 0 Total number of fish 119 155 206 372 298 136 190 1476 0 Total number of species 12 15(6)* 9(2) 12(2) 13(0) 8(1) 9(0) 23 Number of transects 2 4 4 4 4 4 4 26 * Numbers in parentheses are new species that quarter .. - = percentage between 0 and 1. \ Table 3 .. Summary of underwater transects for Rockfish Reef from fall 1981 through summer 1983 .. Numbers for each species represent total seen per quarter .. Fall Winter Spring Summer Fall Spring Summer Total Species 1981 81-82 1982 19R2 1982 1983 1983 n = %
Sebastes mystinus 61 58 78 98 212 69 112 688 49 Sebastes serranoides 52 43 65 83 140 43 89 515 37 Phanerodon furcatus 12 12 24 2 Brachyistius frenatus 0 0 Hypsurus caryi 5 31 5 41 3 Sebastes atrovirens 0 Embiotoca jacksoni 2 12 2 16 1 Ophiodon elongatus 1 3 2 5 8 3 22 2 Hexagrammos decagrammus 1 2 1 1 2 1 8 1 Sebastes melanops 3 1 1 5 Hyperprosopon argenteum 2 2 Oxyjulis californica 0 w Sebastes auriculatus 2 1 2 3 2 2 12 1 w Sebastes chrysomelas 2 3 3 2 3 5 3 21 1 Sebastes caurinus 3 1 4 Sebastes miniatus 3 2 2 7 Damalichthys vacca 2 2 Rhacochilus toxotes 1 1 2 Sebastes pinniger 4 2 2 8 1 Embiotica lateralis 2 3 5 Cymatogaster aggregata 0 Scorpaenichthys marmoratus 2 1 1 4 Sebastes nebulosus 1 1 2 Sebastes rasterlliger Total number of fish 129 135 163 260 367 137 218 1409 Total number of species 10 12(4)* 11(2) 14(3) 9(0) 10(1) 10(0) 20 Number of transects 2 4 4 4 4 4 4 26 *Numbers in parentheses are new species that quarter. -=percentage between 0 and 1. Table 4 .. Summary of underwater transects for Tankhouse Rock from fall',l981 through summer 1983 .. Numbers for each species represent total seen per quarter ..
Fall Winter Spring Summer Fall Spring Summer Total Species 1981 81-82 1982 1982 1982 1983 1983 n = %
Sebastes mystinus 12 41 53 75 41 74 88 384 26 Sebastes serranoides 33 35 48 63 16 61 45 301 20 Phanerodon furcatus 78 65 106 55 66 112 95 577 39 Brachyistius frenatus 61 12 12 85 6 Hypsurus caryi 3 10 7 20 1 Sebastes atrovirens 0 Ernbiotoca jacksoni 1 7 8 16 1 Ophiodon elongatus 3 4 2 1 1 1 12 1 Hexagrammos decagrammus 1 2 J 1 1 2 1 11 1 Sebastes rnelanops 5 1 1 7 Hyperprosopon argenteum 10 10 1 Oxyjulis californica 7 7 Sebastes auriculatus 2 2 2 1 7 w -I>- Sebastes chrysomelas 1 1 1 1 4 Sebastes caurinus 0 Sebastes rniniatus 1 1 Damalichthys vacca 0 Rhacochilus toxotes 1 1 Sebastes pinniger 0 Embiotica lateralis 2 2 Cymatogaster aggregata ·4 4 Scorpaenichthys marmoratus 1 1 1 2 5 Sebastes nebulosus Sebastes rastrelliger 2 1 1 2 3 1 10 1 Total number of fish 138 151 281 246 161 260 237 1474 Total number of species 7 7(3)* 8(2) 18(7) 15(1) 9(0) 10(0) 20 Number of transects 2 4 4 4 4 4 2 24 * Numbers in parentheses are new species that quarter. - = percentage be tween 0 and 1 .. Table 5 .. Summary of underwater tr~nsects for marked· artificial ·reef from fall 1981 through summer 1983 .. Numbers for each species represent total seen per quarter. Fall Winter Spring Summer Fall Spring Summer Total Species 1981 Rl-82 1982 1982 1982 1983 1983 n = %
Sebastes mystinus 120 102 213 705 98 262 1500 32 Sebastes serranoides 51 310 93 203 94 75 185 1011 21 Phanerodon furcatus 17 7 230 58 61 212 738 16 Brachyistius frenatus 0 Hypsurus caryi 9 50 23 120 68 4 71 345· 7 Sebastes atrovirens 20 20 Embiotoca jacksoni 22 101 31 18 186 3 4 365 8 Ophiodon elongatus 3 1 7 8 4 5 28 1 Hexagrammos decagrammus 1 2 8 7 2 20 Sebastes melanops 2 3 1 12 18 Hyperprosopon argenteum 200 43 5 18 140 406 9 Oxyjulis californica 0 w Sebastes auriculatus 1 2 3 31 1 3 6 47 1 l.11 Sebastes carnatus 2 3 2 7 Sebastes chrysomelas 2 1 2 4 9 Sebastes caurinus 1 3 4 Sebastes miniatus 2 4 6 Damalichthys vacca 42 3 5 88 5 143 3 Rhacochilus toxotes 1 1 6 8 Sebastes pinniger 2 4 2 8 Embiotica lateralis 2 12 14 Cymatogaster aggregata 2 2 4 Scorpaenichthys marmoratus 1 4 1 2 8 Sebastes nehulosus 0 Sebastes rasterlliger 0 Total number of fish 285 833 256 884 1222 296 925 4709 Total number of species 7(7)* 13(8) 7(0) 16(5) 14(0) 16(1) 16(0) 21 Number of transects 2 8 2 4 9 2 4 31
* Numbers in parentheses are new specfes that quarter .. - = percentage between 0 and 1. Table 6. Summary of underwater transect cumulative totals for all reefs from fall 1981 through summer 1983 .. " Rockfish Tank house All natural Artificial Surfer Reef Reef Rock reefs totalled reef Species II/% 11/% II/% II/% II/%
Sebastes mystinus 602/41 688/49 384/26 1674/38 1500/32 Sebastes serranoides 387/26 515/37 30/20 1203/28 1011/21 Phanerorlon furcatus 59/ 4 24/ 2 577/39 660/15 738/16 Brachyistius frenatus 73/ 5 0/ 0 85/ 6 158/ 4 0/ 0 Hypsurus caryi 74/ 5 41/ 3 20/ 1 115/ 3 345/ 7 Sebastes atrovirens 110/ 7 0/ 0 0/ 0 110/ 3 20/ - Embiotoca jacksoni 14/ 1 16/ 1 16/ 1 46/ 1 365/ 8 Ophiodon elongatus 25/ 2 22/ 2 12/ 1 39/ 1 28/ 1 Hexagrammos decagrammus 10/ 1 8/ 1 11/ 1 29/ 1 20/ - Sebastes melanops 10/ 1 5/ - 7/ 1 22/ 1 18/ - Hyperprosopon argenteum 8/ 1 2/ - 10/ 1 20/ - 406/ 9 Oxyjulis california 12/ 1 0/ 0 7/ - 19/ - 0/ 0 w Sebastes auriculatus 11/ 1 12/ 1 7/ - 30/ 1 47/ 1 (]\ Sehastes carnatns 29/ 2 21/ 1 10/ 1 60/ 1 7/ - Sebastes chrysomelas 19/ 1 21/ 1 4/ - 44/ 1 9/ - Sebastes caurinus 1/ 4/ 0/ 0 5/ 4/ Sehastes miniatus 12/ 1 7/ - 1/ - 20/ - 6/ - Damalichthys vacca 4/ - 2/ - 0/ 0 6/ - 143/ 3 Rhacochilus toxotes 2/ - 2/ - 1/ - 5/ - 8/ - Sebastes pinniger 6/ - 8/ 1 0/ 0 14/ 0 8/ - Embiotoca lateralis 3/ - 5/ - 2/ - 10/ - 14/ - Cymatogaster aggregata 0/ 0 0/ 0 4/ - 4/ - 4/ - Scorpaenichthys marmoratus 3/ 0 4/ 0 5/ - 2/ - 8/ - Sebastes nebulosus 2/ - 2/ - 0/ - 4/ - 0/ 0 Sebastes rastrelliger 0/ - 0/ 0 10/ - 10/ - 0/ 0 Total number of fish 1476 1409 1474 4319 4709 Total number of species 23 20 20 25 21 Total number of transects 26 26 24 74 31 - = percentage between 0 and 1 .. 2 Table 7. Estimated mean densities (#/m ) + standard deviation for all fish observed on underwater tran- sects from fall 1981 through summer 1983 in Soquel Cove on the artificial and natural reefs. Statistical comparison of natural reef versus artificial ~eef using single factor ANOVA.
Fall Winter Spring Summer Fall Spring Summer Combined totals 19tH 1981-82 1982 1982 1982 1983 1983 1981-1983
Surfer Reef 1.<}6+.68 1.27+.29 1.69+.27 3.05+.49 2.45+.30 l • 12+. 1 7 l. 56+. 4 l 1.87+.68 ** **- No. of transects 2 *4 4 4 4 4 4 **26
Rockfish Reef 2 .12+. 39 1.11+.22 1 .34+. l 8 2 .14+. 21 3.02+.27 l . 13+. 21 1.79+.21 1.81+.69 ** ** No. of transects 2 *4 4 4 *4 **4 **4 26
Tankhouse Rock 2.34+.47 1. 34+. 21 2.31+.51 2.38+.27 I • 32+. 3l 2. I 3+. 31 3.89+.31 2.24+.86 * ** ** ** No. of transects 2 4 4 '• 4 *4 *2 24 Artificial reef 4 .68+.49 3.42+.69 4.20+.85 7.25+1.39 4.45+1.01 4.86+.91 7. 70+.86 5.31+1.5
No. of transects 2 8 2 4 9 2 4 31 Table 8. Summary of tagged fish from natural ree~s.
Tankhouse Rock Rockfish Reef Surfer Reef Adams Reef Soquel Point Totals II fiR % II IlK % tl IIR % II fiR % II fiR i. # fiR %
Sebastes mystinus 12 25 l 4 39 7 17.9 49 3 6 125 11 8.8 Sebastes carnatus 7 14.3 28 2 7. 1 9 5 55.6 7 l 14.3 51 9 17.6 s. auriculatus 4 6 16.7 15 3 20 17 7 41.2 42 ll 26.2 ~· chyrsomelas 1 2 5.0 l l 2 18.2 2 1 5.0 16 5 31.3 s. serranoides 1 7 3 11 0 0 Ophiodon elongatus 3 2 l 2 8 0 0 S. miniatus 1 4 2 50 5 2 40 S. melanops l 2 4 0 0 s. atrovirens 4 4 0 0 llexagrammos decagrammos 2 l so 2 l 50 S. caHrinus l 0 0 1 2 0 0 s. pinniger l 1 0 0 w s. nebulosus l 0 0 CP
Total 31 3 9.7 66 5 7.6 88 19 21.6 A3 12 14.4 4 272 39 14.3
fl "' number tagged 1/R "' number recaptured % percentage of total tagged. fish of that species recaptured 39
Table 9. Totals of fishes that had moved from natural reefs to the artificial reef.
II Total tagged %
s .. mystinus 9 125 7.2 s. auricula tus 9 42 21.4 s .. carnatus 6 51 11.8 s. chrysomelas 4 16 25.0 s .. miniatus 2 5 40.0 H. decagram.mus 1 2 50.0
Total 31 24 272
31/39 (total recaptured fish) = 79.5% of recaptured fish moved from the natural reefs to the artificial reef. 40
Table 10. Underwater observations of tagged fish from April 1982 through July 1983.
No. of observations Movement
Tankhouse Rock
S .. mystinus 4 None S. carnatus 2 None S. auriculatus 2 None
Rockfish Reef
S. carnatus 8 None S .. mystinus 6 None S .. auriculatus 2 None S. chrysomelas 1 None
Surfer Reef
S. mystinus 9 8 - no movement 1 - could not see color of tag S .. auriculatus 5 No movement S. carnatus 3 2 - no movement 1 - moved from Rockfish Reef S .. serranoides 3 No movement
Total observations 41
Table 11. Percent Similarity Index for the two sampling methods -- hook-and-line, and underwater transects -- used on the four natural reefs. Percentages are from cumulative percentages for period 1981-1983 ..
Hook-and-line Underwater Species sampling % transects %
Sebastes mystinus 45 38 Sebastes serranoides 4 28 Phanerodon furcatus 0 15 Brachyistius frenatus 0 4 Hypsurus caryi 0 3 Sebastes atrovirens 1 3 Embiotoca jacksoni 0 1 Ophiodon elongatus 3 1 Hexagrammos decagrammus 1 1 Sebastes melanops 1 1 Hyperprosopon argenteum 0 Oxyjulis california 0 Sebastes auriculatus 15 1 Sebastes carnatus 18 1 Sebastes chrysomelas 6 1 Sebastes caurinus 0 Sebastes miniatus 2 Damalichthys vacca 0 Rhacochilus toxotes 0 Sebastes pinniger Embiotoca lateralis 0 Cymatogaster aggregata 0 Scorpaenichthys marmoratus 0 Sebastes nebulosus Sebastes rastrelliger 0
No .. of species 13 25
PSI .50 % between 0 and 1 42
FIGURES CAPITOLA
/.& I
ROCK .~q,. o•o' ARTIFlCW. REEF
-----IS."Z.;
SOQUEL POINT REEF/""'
ADAMS REEF .30
Fig. 1. Map showing location of artificial and natural reefs. 44 2~~------~------.------r------.------.
co G> •...C .. ·I 0 . 1 ... CD Q._ (.f) 4- 0 L G> ...0 E z:~ CD > •...C +> 0 ...... ~ E w~
1 2 3 4 Transect Number ·(Summer 1982)
20~------~------~------r------.------,
w .....CD 0 CD Q._ (.f) 4- 0 .,.. A------1------+ L .,.. CD .,.. .,.. .,.. · ec Tankhouee Rock ...0 .,.. E ..,... .,.. .,.. +• Surfer Reef z:~ CD .....> +> 0 ...... ~ E w:>
1 2 3 Transect Number (Summer 1982)
Fig. 2. Cumulative number of species for the four transects conducted in the summer of 1982 on the natural and artificial reefs. 0') Q) 20 ...... 0 Q) Q_ U) 16 4- 0 L Q) _.o # = Rockfish E 12 ::) :z Q) :4 = Artificial Reef .....> 8 -4-> 0 % ...... , ::) E J u 4
~~----~----~----~-----L----~----~L-----L---~ 24~--~----~----~----~----~----~----~----~ ---+-----+ .,..+-----+--
..... • .-4 ..... 0 "" CD tr"" Q_ / U1 / / * = Tankhouse Rock 4- / 0 / I = Surfer Reef L I + CD I _o 4 E ::) z: CD ...... > -4-> 0 :::> E :::> u
F 82 Su.83
Fig. 3. Cumulative species curves for the three natural reefs and the artificial reef .. Naturals Artifici.al Tankhouse Surfer Rockfish combined Summer 1982 Artificial reef • 79 .61 .. 69 .. 71
Tankhouse .. 28 .67 .. 70
Surfer .21 .35 .66
Rockfish .. 18 .34 .81
Fall 1981 Naturals combined .24
Artificial reef
Tankhouse
Surfer
Rockfish·
Cumulative Naturals combined Total 1983
Note: no comparison was made.
Figures 4 and 5. PSI values for fall 1981, summer 1982, and cumulative total from 1981-1983. 47
71
Roc:kf a eh Reef Ton!-thouse Roch ~ - ..... -
- - 1- - liS (2. f.:, 'r]t tOt l..3 I 'f'f 13 g 35''1 2 ( s- - - - [Cf4 ¥S lZ Z.. t5Z.. - .... tS''f - """ ~h 1- - .... - ~ UJ - Ul - I - - r r _t:., I r r I r f r a1 w BJ S 82 S 82 F 82 S 133 S 83 f 81 w 81 s 82 SB3 s 83
- Arttflclol Rear - Surfer- Reef '-rr; - - - 17 B - - 5"2 Ba2 - r'i2 'fS'(, 187- - '- J.{~f - """ /0 I Gtct 13o i- - 2-ftj 19( f- - 2'Ft e- - ..... - - - - """ - 1 - .... - - j - - - U! - - - r - ~ n ~ r ·-- ~ r j F 81 lit 81 S 1:12 S82 f82 Sl33 I ~ F 81 W81 582 . Sv82 FB2 583 Su83
s em M el'll L 12-20 em X >20 om SMLX
Fig. 6. Percentages of rockfish from the four size classes seen on underwater transects 1981 through 1983. Numbers listed are absolute numbers per quarter. 16~~------~-r~~~
1
1
1 ......
...... LL. }- /~ I 'r .. I.+······· ,....
Mont in 1982-
Fig. 7. Mean number of estimated hours of fishing pressure~ standard error for the natural and artificial reefs. ci d ui ui .... +I ' 5 a.~- J Rockfish Reef 0 0 ..!:. ..c. Tonkhouae Rock L L 111 ~ 6.111- c 0 L •a.. ..c. Ill 4- 4- 0 4- 0 ' Ill L ..0 Ill E ..0 J :z z~
d d ui u1 +I +I 5 Ad0111e Reef _g
' Ill 01c 0 '- 111a.. .L ell 4- 4- 0 L 411 ..0 1!1 £ LI~L-~~~~~~~~~~~~~~~~~ B. 9 1!...-1.-1..-"-....1.-.IL.-lL.....J..--L-L-.l-~--L-L-L-..L_L-J.--L.....J F M A H J J A S 0 N 0 J F M A H J J F M A MJ J A 5 0 N 0 J F M A MJ J Monthe in 1982-83 Monthe in 1982-1983
Fig. 8. Mean number of fish per angler hour + standard deviation for each month from February 1982 through July 1983 on the four natural reefs. 50
APPENDIX 51
Appendix 1 .. Size, date tagged, days at liberty, date recaptured, and movement noted for recaptured fishes from all natural reefs.
Movement Size Date Days at Date A .. R. = arti- (em) tagged liberty recapt .. ficial reef
Tankhouse
H. decagrammus 28 4/82 40 5/82 ** to A.. R .. s .. ·chrysomelas 26 6/82 50 8/82 ** to A.R. s. carnatus 24 2.82 160 7/82 ** to A.. R.
Rockfish Reef s .. carnatus 26 7/82 34 8/82 ** to A .. R. s. carnatus 28 5/83 61 7/83 No movement s. mystinus 27 5/83 64 7/83 ** to A. R. s. auriculatus 32 5/83 70 7/83 ** to A .. R. s. chrysomelas 25 5/83 49 7/83 No movement 60% of fish recaptured moved N .. R.--) A .. R.
Surfer Reef s. auriculatus 26 5/82 19 6/82 ** to A.R .. s .. auricula tus 33 7/82 18 8/82 ** to A.. R .. s. auriculatus 30 5/82 367 5/83 ** to A.. R. s. carnatus 23.5 9/82 293 7/83 No movement s .. carnatus 25 7/82 28 8/82 ** to A.R. s .. carnatus 24 4/82 36 5/82 ** to A .. R .. s .. carnatus 31 6/82 361 6/83 No movement s. carnatus 29 7/82 349 7/83 ** to A.. R .. s. chrysomelas 24 .. 5 3/82 53 5/82 ** to A.. R .. s. chrysomelas 23 7/82 13 7/82 ** to A.. R .. s. miniatus 34 8/82 9 8/82 ** to A.. R. s .. miniatus 35 8/82 9 8/82 ** to A .. R. s .. mrstinus 23 8/82 70 11/82 No movement s. mystinus 28 7/82 37 8/82 ** to A .. R.. s .. mystinus 19 3/82 47 5/82 ** to A.. R .. s .. mystinus 29 .. 5 4/82 63 6/82 ** to A .. R.. s. mystinus 28 7/82 21 7/82 ** to A.R .. s .. mystinus 24 9/82 14 9/82 ** to A.R .. s .. m;r:stinus 28 10/82 273 7/83 No movement 52
Appendix 1 - cont 'd,.
Movement Size Date Days at Date A .. R. == arti- (em) tagged liberty recapt .. ficial reef
Adams Reef s. auriculatus 26 2/82 126 6/82 ** to A.. R .. s .. auriculatus 29 3/82 75 6/82 No movement s .. auriculatus 27 4/82 28 5/82 ** to A.R. s~ .. auriculatus 25 4/82 21 5/82 ** to A .. R .. s .. auriculatus 31 3/82 12 3/82 ** to A.R .. s. auricula tus 24 5/83 41 6/83 ** to A.R. s. auriculatus 31 4/82 394 6/83 No movement s. carnatus 28 6/82 372 6/83 ** to A.R .. s .. chrysomelas 28 5/82 56 7/82 ** to A.R. s .. mystinus 28 9/82 28 10/82 ** to A .. R .. s .. m~stinus 27 9/82 17 9/82 ** to A.R .. s. mystinus 32 9/82 264 6/83 ** to A.R ..
A.R. artificial reef