VIRGIN ISLANDS RESOURCE MANAGEMENT COOPERATIVE BIOSPHERE RESERVE RESEARCH REPORT NO.22 A BASIS FOR LONG-TERM MONITORING OF FISH AND SHELLFISH SPECIES IN THE VIRGIN ISLANDS NATIONAL PARK Ralf H. Boulton, Jr. V.1. Division of Fish and Wildlife Department of Planning and Natural Resources St. Thomas, U.S. Virgin Islands Virgin Islands National Park August, 1987 A BASIS FOR LONG-TERM MONITORING OF FISH AND SHELLFISH SPECIES IN THE VIRGIN ISLANDS NATIONAL PARK BIOSPHERE RESERVE REPORT NO. 22 RALF H. BOULON, JR. V.I. DIVISION OF FISH AND WILDLIFE DEPARTMENT OF PLANNING AND NATURAL RESOURCES ST. THOMAS, U.S. VIRGIN ISLANDS U.S. DEPARTMENT OF THE INTERIOR NATIONAL PARK SERVICE AND VIRGIN ISLANDS RESOURCE MANAGEMENT COOPERATIVE VIRGIN ISLANDS NATIONAL PARK P.O. BOX 7789, ST. THOMAS U.S. VIRGIN ISLANDS 00801 LOCAL CONTRACTING AGENT ISLAND RESOURCES FOUNDATION RED HOOK BOX 33, ST. THOMAS U.S. VIRGIN ISLANDS 00802 (NPS CONTRACT NO. CX-0001-3-0048) Abstract A long-term monitoring program was initiated for fish and invertebrate species of commercial importance within the Virgin Islands National Park/Biosphere Reserve. Additionally, generally surveys were made for lobsters and conch. Hopefully, the data obtained will begin to fulfill the need for quantitative baseline data to assess and manage these resources adequately. A one~year study indicates that; 1) some species of reef fish may have seasonal trends in numbers; 2) the inshore spiny lobster (Panulirus argus) population shows summer and winter peaks at Fish Bay but not Reef Bay, where numbers are very low; 3) conch (Strombus gigas) show a definite seasonal trend in deeper water with low numbers during the summer reproductive season; 4) whelk (Cittarium pica) at one study site show a large annual cohort of juveniles decreasing in abundance with increasing size. Few adults are present due to natural mortality. General surveys for conch and lobster demonstrate that the populations are of low abundance and highly dispersed. These data will be useful to assess population trends in the absence or presence of management actions on the species or species groups. Recommendations for monitoring methodologies and management actions are discussed. Acknowledgements I would like to acknowledge and extend my deep appreciation to University of the Virgin Islands students, Lauren Patterson and Sue Johnson, and National Park Service technicians, Vonnie Zullo and John Blount, for their very valuable assistance in the field. Special thanks to Jim Beets of the University of Georgia for his discussions on this study, his help in the field, and his analysis of the data. Statistical analyses of the data were completed using STATPRO on an Apple computer and SYSTAT on an IBM PC. ii Table of Contents Abstract Acknowledgments Table of Contents List of Tables List of Figures Introduction Reef Fish Methodology Hawksnest Bay Reef Bay Fish Bay General Conclusions Lobster - Panulirus argus and P. guttatus Methodology Reef Bay FishBay Hawksnest Bay General Surveys General Conclusions ~ Strombus gigas Methodology Reef Bay Hawksnest Bay Fish Bay Threadneedle Bay General Surveys General Conclusions - Cittarium pica Methodology Results General Conclusions Summary Conclusions Monitoring Recommendations Management. Recommendations Literature Cited Appendix Ia~- Reef Bay lobster study site diagram Appendix Ib - Fish Bay lobster study site diagram Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table 6. 8. 9. 10. 11. 12. 13. 14, 15. List of Tables Commercially important species of fish observed at the long-term monitoring study sites. Average number of fish per census per species for Hawksnest Bay Shallow Bay Patch Reef (SBpr) from March 1985 to February 1986. Zone and subzone designations with acronyms. Average number of fish per census per species for Hawksnest Bay southern fringing patch reefs (Rfu) from March 1985 to February 1986. Average number of fish per census per species for Hawksnest Bay eastern fringing patch reef (Rfu) from March 1985 to February 1986. Average number of fish per census per species for Reef Bay lower forereef (R£1) from February 1985 to January 1986. Average number of fish per census per species for Fish Bay lower forereef (Rf£1) from January 1985 to January 1986. Average number of fish per census per species or Fish Bay backreef (Rb) from January 1985 to January 1986. Sample statistics for each of the long-term reef fish monitoring sites on St. John, USVI. Numbers of spiny and spotted lobster by two size classes per sample date for two long-term monitoring sites on St. John, ysvt. Results of general lobster surveys around St. John, USVI during the summer of 1985. Numbers of adult and juvenile conch per sampling date for three long-term monitoring sites, St. John, USVI. Results of conch tows duplicating thoge made in 1981 by Wood and Olsen (1983). Results of general conch surveys around St. John, USVI during the summer of 1985. Numbers and relative abundance of whelk per size clase on four sample dates at Windswept Beach, St. John, USVI. iv ll. 14, 16. 19. 23. 27. 29. 32. 34. 39. 43, 48. 49, 55. Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 4. 6. 8. 9. 10. il. 12. List of Figures Map of St. John, USVI showing location of study sites. Cumulative percent species curve for ten repetitive fish censuses at one location in Fish Bay, St. John, USVI on January 22, 1985. Hawksnest Bay, St. John, USVI showing location of study areas for long-term monitoring of reef fish and lobster populations. Reef Bay, St. John, USVI showing location of atudy site for long-term monitoring of reef fish and lobster populations. Fish Bay, St. John, USVT. showing location of study sites for long-term monitoring of reef fish, lobster and conch populations. Numbers of spiny and spotted lobster per sample date for two long-term monitoring sites, St. John, USVI. Location of general lobster surveys, St. John, USVI. Numbers of adult and juvenile conch for three long-term monitoring sites on St. John. USVI. Threadneedle Bay, St. John, USVI showing location of study site for long-term monitoring of conch population. Location of conch tows and general surveys, . St. John, USVI. Windswept Beach, St. John, USVI showing location of study site for long-term monitoring of conch populations. Size frequency of whelks collected at Windswept Beach, St. John, USVI on four sampling occasions. 10. 22. 36. 38. 44, 45. 47. 53. 56. Introduction Fish and marine invertebrates in the Virgin Islands are being affected by a number of stresses. Foremost of these is the heavy fishing pressure exerted on most species. With a limited shelf area of approximately 160,000 hectares (St. Thomas and St. John) and a total of 255 registered commercial fishermen (St. Thomas and St. John) for 1984-85 (Clavijo, et al., 1986), not to mention an unknown number of recreational fishermen and sport divers, the reef fish, lobsters, conch and whelk are being harvested at a rate exceeding replacement. As a result the stocks are declining at an alarming rate (Caribbean Fisheries Management Council (CFMC), 1985), a fact corroborated by fishery landings data as well as by fishermen. Other stresses include effects of development (sedimentation, increased runoff, potential toxic pollutants) and habitat degradation through anchor and boat damage and large numbers of visitors utilizing and affecting the marine ecosystems. As it is very difficult to estimate accurately the total potential fishery yield of tropical insular shelf marine environments, many fisheries have been overexploited both biologically and economically before the condition is realized. Management is, therefore, a necessary tool in mitigating adverse conditions in a fishery. A prerequisite to developing management plans is to have information on the status of the fishery unit in question. The Caribbean Fishery Management Council (1985) lists as its number one problem the insufficiency of data needed for long-range management. This need can be satisfied by obtaining these data through research and surveys. With this information, Management actions can be formulated to restore and maintain adult stocks at levels that ensure adequate spawning and recruitment required to maintain the population. This is accomplished through the promulgation of laws which prevent the harvest of individuals of species of high value by enforcement of minimum size restrictions and/or closed seasons. Monitoring the effects of a management action is essential in order to determine the success of the action and to assess the need for modification of regulations. While stresses due to adverse fishery conditions can be mitigated (although not without upsetting the segment of the population involved in the fishery), it is harder to control and mitigate the more subtle stresses of development. This is an area where control of continuing development is probably impossible and mitigation would be extremely costly. Our goal must be to measure the effects and work for establishment of restrictions on development in productive areas. The main objective of this study was to select areas within the National Park for long-term monitoring of fish and marine invertebrates. Reef fish, lobster, conch, and whelk were selected as high value species to be monitored in bays associated with disturbed and undisturbed watersheds. The data to be collected are to be used as baseline data for formulating and monitoring recommended management actions. Monitoring methodologies were developed which could be easily used and taught to non-scientists yet yield accurate results. These methods could be used throughout the Caribbean to produce comparable data bases in areas with little technology or resources. Reef fish Methodology Three main watershed areas have been selected within the National Park for long-term study. These include Reef Bay (a completely protected watershed), Fish Bay (a watershed under development), and Hawksnest Bay (potentially impacted by construction of the St. John Clinic and future development) (Figure 1). Therefore, these bays were selected for long-term reef fish monitoring. Primary reef fish habitats were selected for monitoring within each bay based on previous designation of fishery habitats (Boulon, 1985a). Species of fish were selected for study on the basis of their importance in the local commercial fisheries (Table 1). Any species taken as a food fish by any means were considered. Nearly all species selected for this project are considered in the Fishery Management Plan for the Shallow-Water reef fish Fishery of Puerto Rico and the U.S. Virgin Islands (CFMC, 1985). The species considered in the Fishery Management Plan were selected out of approximately 180 species which are landed and used in quantity throughout the Caribbean. A census was taken of fish species of commercial importance present in the selected habitat within each of these bays using a random point, visual census technique (Bohnsack and Bannerot, 1983). Census locations were selected on a random basis within a habitat. The attempt was to locate oneself in a site characteristic of the selected habitat. It is important to avoid mixing the habitats (e.g. lower forereef and sand) within a single census radius. At each census location, the observer would begin by facing in one particular direction and during a five-minute period, rotate clockwise 360°, sampling all fish within an eight meter radius cylinder surrounding the observer. Due to good water clarity, an 8m radius could be used in all study sites. As the observer rotated through the census, the number of individuals observed for each species was recorded on mylar over a preprinted form. The preprinted form saves time in writing down the species’ name. After using this form a few times, the location of a species' name is easily remembered. Use of the preprinted form did not appear to produce a bias (Bohnsack and Bannerot, 1983) since the form is only looked at to write down fish just observed and does not cause the observer to select fish to look for. This method proved more reliable in our study. The chance of counting an individual twice was greatly reduced by strictly adhering to the 360° census with no overlap and avoidance of recounting in subsequent censuses obvious *soats Apnyas jo woz e.OT BuyMoys *TAsn ‘uyor ‘ag go dew ‘] ean3zgq Od NHOF ‘LS aod adamsputmM Aeg aT prxaeupes1 yy +=z RAL) TABLE 1. Commercially important species of fish observed at the long-term monitoring study sites. Common and scientific names taken from Robins, et al. (1980). Local common names from J.A. LaPlace (pers. comm.). COMMON NAME ee ee ee ee ee LATIN NAME COASTAL PELAGIC FISH: cero mackerel horse-eye jack bar-jack-carang DEMERSAL FIN FISH: queen triggerfish - old wife biuestriped grunt white grunt french grunt tomtate smallmouth grunt spanish grunt striped grunt sailor's choice juvenile grunts margate mutton snapper - virgin snapper dog snapper ~- dogtooth snapper grey snapper schoolmaster ~- mango snapper yellowtail snapper mahogany snapper - burn tail lane snapper - pot snapper queen & french angelfish - swede angel grey angel - flatfish rock beauty - black and yellow swede red hind - hind rock hind graysby ~- butter socks coney - butter fish nassau grouper black grouper tiger grouper porgies surgeonfish — a me. ee et ee ee Scombero Caranz_1 C._ ruber Balistes_vetula Haemulon sciurus H. plumieri H. flavolineatum H. aurolineatum H. macrostomum H._ striatum H. _parra H. spp. H, album Lutjanus analis L. jocu L._griseus L. apodus Ocyurus_chrysurus L. mahogoni L._synagris Pomacanthus spp. Sa Epinephelus guttatus E._adscensionis Petrometopon cruentatum Cephalopholis fulva Ephinephelus striatus Myctoperca_bonaci M. tigris Sparidae Acanthurus spp. Table 1. (Continued) Commercially important species of fish observed at the long-term monitoring study sites. Common and scientific names taken from Robins, et al. (1980). Local common names from J.A. LaPlace. (pers. comm.). ~ —— COMMON NAME LATIN NAME DEMERSAL FIN FISH: (continued) blue tang - blue doctor yellow goatfish - queen mullet spotted goatfish spanish hogfish ~- spanish piper hogfish ~- eaglemouth Lac parrotfish - goutou Scaridae trunkfish - shellfish Ostraciontadae sea chubs Kyphosus spp. barracuda Sphyraena barracuda squirrelfish Holocentridae glasseye/bigeye - bleareyes Priacanthus spp. mojarra - sand diggers Gerreidae of species that tend to be very mobile (e.g. mutton snapper, barracuda). At the end of a sample period, the minimum and maximum lengths for each species were recorded. Where a clear dichotomy in sizes was observed, this was noted. These lengths are estimates based on pre-study tests and extensive field experience in which estimates were made of objects at various distances from the observer and then measured to determine accuracy. When other observers were used, size estimates were examined for consistency with data collected by the author and discrepancies were discussed with the other observer. Most species of fish occurred in low numbers during a census. Schools of fish are counted as they appear in the sample radius and if large, ere counted in 10s, 100s or even 1000s. Advantages of this method are numerous. It is simple, rapid, unbiased and precise. It is easily performed by anyone with a minimum of instruction and practice. It requires no complicated accessories such as cameras, transect lines, compasses, etc. As such, it is very applicable to developing countries where technology is not available for higher~tech methods requiring many accessories. It is easily performed either by snorkeling or using SCUBA (for depths greater than 4m). A stationary observer has a better chance of observing more cryptic or wary species which would otherwise avoid a moving diver. There are also species which are attracted to a moving diver, thus biasing the data. Additionally, due to the small area actually sampled in one census, the chances of crossing habitats within a census are greatly reduced. The only requirement of this method is an underwater watch and an ability to identify fish species using external morphological or visual characteristics. This is easily accomplished after several practice censuses with review and reference of a good identification guide (e.g. Randall, 1968; Chaplin, 1972; Stokes, 1980). Several disadvantages of this direct sampling method must be acknowledged. Using this method, nocturnal and highly cryptic species tend to go undetected. Being a random point census technique, the effects of schooling, territoriality or preference for specific microhabitats (all of which can cause nonrandom distribution of fish populations) can affect abundance estimates. Also, juvenile fishes tend to be underrepresented. However, ensuring that censuses are performed in habitat "core areas" (Boulon, 1985a) will eliminate the significance of these problems. A preliminary test was made of this method to determine number of censuses necessary to accurately describe an area in terms of species composition. Ten successive censuses were made in one location. The results indicate that approximately 80 percent of the resident, nonmigratory and non~cryptic species are observed in four censuses (Figure 2). Species added in subsequent censuses include migratory species such as mackerel OL “G86T °ZZ Aqenuep uo *TASN Suyor *3g ‘Aeg USTZ UT UOT}EOCT suo Fe SasNsusd YSTF eAT}THeder Uda} TOF eA setoads jueoszed eat eTNUMND S3SNSN4I9 °ON 8 Z 9 g v i i 2 i i POS ~OOL ‘wung salsedg % (Scomberomorus maculatus) and cryptic species such as small coney (Epinephelus fulvus), whose behavior is to hide behind coral heads and peek out frequently unobserved. Based on this study and the size of most of the areas monitored, ten censuses per location per date was selected as an adequate sample size to yield a representative sample of the fish assemblage composition and abundance within that particular habitat. At certain selected locations the reef or habitat being sampled was smaller in size and fewer censuses were needed to adequately cover the area without overlap. Hawksnest Bay Hawksnest Bay, on the north shore of St. John (Figure 3) was chosen as a long-term monitoring site for two reasons. First, it is an area suspected of having been affected by sedimentation produced by the construction of the St. John Community Health Clinic in 1982 at the top of this watershed. Unstabilized sediment berms created by the excavation for the hospital have been steadily eroding since 1982 and may have raised the sediment load of the bay, decreasing visibility (light transmission) and taxing the sediment removal capabilities of benthic organisms. Changes in benthic communities would be reflected in long-term changes in reef fish assemblage composition and abundance. The second reason for selecting Hawksnest is that other long-term coral and sedimentation studies were initiated in the watershed and an integrated view is evolving. Three areas in the bay, representing two different habitat types, were selected for this study. Shallow bay patch reef-SBpr Located in the middle of Hawksnest Bay (Figure 3) this reef is approximately 75m long and 30m wide with the long axis oriented North-South. It is characterized by having an east facing forereef which rises up from a 12m deep sand plain to about 9m. This forereef, with its vertical relief and moderate coral coverage, has the greatest abundance of fish on the reef. Behind this the reef is relatively flat with scattered corals, gorgonians, and sponges. The back of the reef (west side) is very sandy with sparse, scattered gorgonians,and few fish. The reef was characterized by monthly samples of five censuses along the forereef and five censuses along the middle portion of the reef. Eleven monthly samples were made (Table 2) on this reef from March 1985 to February 1986. A total of 36 species of commercially important fish were observed on the reef during this period with a mean of 21.4 (sd=2.19) species seen on each sample date. A mean of 428 (sd=127) individual fish were seen on each sample date. Mean average fish size for the entire period was 5.8 (sd=0.6) inches. Of the 36 observed species, 20 species were present in eight (75%) or more samples and eight species were present in every sample. No trends are evident for species abundance or average fish ' 64°47 Marine Benthic Communities | St. John, USVI 100 200 300 ! j | py O . 100 200 306 1 r J Scaie in Meters 2—— ero Seurce: Aerial Photographs, NOS 1983} White Clitts 18°10! 64°as’ Figure 4, Reef Bay, St. John, USVI, showing location of study site for long-term monitoring of reef fish and lob- ster populations. @- study area. eae - conch survey area. See Table 3 for acronyms. 22 TABLE 6. Average number of fish per census per species for Reef Bay lower fore reef (Rf1) from February 1985 to January 1986. (Total # fish/# censuses). a ee ae eer ee ee ee ce ew ee ee Oe Species 2/85 4/85 6/85 7/85 8/85 9/85 10/85 12/85 1/85 cucen tliggetfish blue striped grunt 2.8 2.4 3.3 2.0 3.3 3.3 3.8 2.0 1.2 white grunt 4.2 6.9 16.9 16.1 8.2 15.9 14.9 6.1 5.3 french grunt 4.8 9.1 11.2 8.2 6.4 13.1 7.3 3.9 5.0 tomtate 2 small mouth grunt 6 -5 1.4 spanish grunt 2 -5 -5 7 2 -6 2 2 2 juvenile grunts 2.8 16.7 6.0 mutton snapper o1 3 ol ol dog snapper el 1 el gray snapper 3 lane snapper el school master 9 4 7 2 1.0 1.1 6 4 4 yellowtail snapper 4.7 3.8 2.4 3.8 1.8 4.7 3.3 4.9 2.5 mahogany snapper 2 2.8 9.2 8.3 2.1 1.0 1.3 5.3 3.8 q & fr angelfish ol ol el 2 el 2 gray angelfish ~2 ol 2 4 red hind el coney 2 2 el ae nassau grouper el el el black grouper 1 2 tiger grouper . 1 ol ol el el el blue tang 4.2 12.9 30.2 11.7 22.7 11.5 7.6 11.1 16.9 23 Table 6 (Continued) Average number of fish per census per species for Reef Bay lower forereef (Rf1) from February 1985 to January 1986. (Total # fish/# censuses). A sree ce cee ee ce me mn cy sins ce neh em cer nas te em nO at st ae tte a et es Sere SN nag MD Se en See ee fees teh mh i at re Sh ns ee wee se ee ee ee ee ee ec eee Species 2/85 4/85 6/85 7/85 8/85 9/85 10/85 12/85 1/86 surgeon fish —~—=«168 6.5. 4:6 911106 508 201 400 4s yellow goatfish 1.4 1.7 3.0 2.5 2.5 3.9 .6 1.1 spotted goatfish 2 <5 6 8 1.5 5.8 1.7 2.0 25 spanish hogfish 3 25 4 1 «2 6 el 2 parrot fish 5.8 11.1 11.7 8.0 11.7 6.2 8.9 11.8 12.1 trunkfish 1 2 1 barracuda 1 -3 squirrel fish «1 +5 1.1 6 8 1.6 1.0 1.2 -6 mojarra «1 ol el 3 e1 mackerel el ol 1.6 bar jack 2.1 4 1.1 3 1.0 1.9 1.1 2 total # species 22 21 22 20 17 25 19 24 19 total # individuals 344 475 964 826 750 815 596 586 555 average size(in) 6.89 5.81 5.77 5.42 6.01 5.01 5.38 6.22 5.86 24 Fish Bay Fish Bay, on the south shore of St. John (Figure 5), was chosen as a long-term monitoring site for two major seasons. First, this is a large watershed which is still relatively pristine but is planned for major residential development (over 200 lots) in the lower part of the watershed. The middle part is owned by the National Park Service and The Nature Conservancy and the upper part is private with potential for additional development. There is therefore potential for major impact on the marine resources of this bay. Secondly, like Hawksnest and Reef Bays, the combination of this study with other long-term research creates a more complete picture of the bay. Two habitats were selected as being the major habitats of importance for reef fish. These include the lower forereef and backreef habitats. The mangroves along the coastline were surveyed for juvenile nursery potential but the extreme shallowness of the water (only a few inches at low tide) makes it unsuitable for fish to reside there. Only a very few fish were observed and those were in small hollows where the gut enters the bay. Visibility in these hollows is not much better than half a meter which makes any survey method nearly impossible. Lower Forereef-Rfl The lower forereef in Fish Bay is a series of spurs oriented northwest to southeast with sand between them (Figure 5). Maximum relief of the spurs is approximately 2m. The study area covers approximately 50 percent of the lower forereef habitat and is llm in depth with a well developed and diverse coral community (Rogers and Zullo, 1986). Ten monthly samples were made (Table 7) on this reef from January 1985 to January 1986. Atotal of 34 species of commercially important fish were observed on the reef during this period with a mean of 16.5 (sd=1.75) species seen on each sample date. A mean of 298 (sd=110) individual fish were seen on each sample date. Mean average fish size for the entire period was 5.49 (sd=.39) inches. Of the 34 observed species, 12 species were present in eight (75%) or more samples and five species were present in every sample. Eleven species were seen only once during the study period. 25 Marine Benthic Communities St. John, USVI Salt Pond | Fish Bay 0 100 200 300 t 4 4 4 if <1 1 Scate in Meters Source: a Aerial Photographs, NO § 1983} Aty SR¢q-Th, Coccolobva Cay Se N e8e . 18°s8 ‘Ne on Sa ~ NPS Boundar _ Lae; an Figure 5. Fish Bay, St. John, USVI, showing location of study sites for long-term monitoring of reef fish , lobster and conch populations. @- fish study areas, @- fish and lobster study areas,X - conch study areas. See Table 3 for acronyms. : 26 TABLE 7. Average number of fish per census per species for Fish Bay lower forereef (Rf1) from January 1985 to January 1986. (Total # fish/# censuses). a a ec ee Species 1/85 3/85 4/85 6/85 7/85 8/85 9/85 10/85 11/85 1/86 queen triggerfish el bluestriped grunt 2 5.1 3 4 4 oi 5 3 white grunt 2.0 4.4 1.5 .3 1.7 1.3 8 4 1.2 french grunt 1.4 4 1.1 7 1.7 1.7 1.5 1.9 2.0 5 tomtate 5.5 spanish grunt ol margate ol mutton snapper -1 el schoolmaster el el 3 2 -5 4 4 el 3 yellowtail snapper 1.7 2.4 8 1.5 1.2 8 1.3 9 1.0 23 mahogany snapper 1.6 2 23 3 q & fr. angelfish el ol ei rock beauty 2 ol red hind ol el ol el ol graysby 23 «1 el 1 el coney 1 ol a2 el 3 3 2 nassau grouper ol black grouper ol tiger grouper ol 2 blue tang 2.5 11.0 4.3 21.6 1.6 4.5 5.0 7.7 4.3 2.4 surgeonfish 3.0 7.5 4.6 8.2 3.3 4.1 6.3 5.6 4.6 5.1 yellow goatfish 1.5 -6 2 23 2 4 spotted goatfish 6 1.4 2 9 1.4 1.0 6.6 1.2 1.2 spanish hogfish ol 4 25 23 2 3 23 ol 2 hogfish ol porgies el 2 parrotfish 4.7 9.4 7.8 9.2 12.3 14.9 6.7 7.5 9.3 6.1 trunkfish el el 2 barracuda . el 1 squirrelfish -3 7 25 25 -3 25 4 6 23 mojarra ol mackerel 2 bar jack 1.0 1.1 2 Pr) 1.8 8 3 8 2 horseeye jack ol total # species 15 13 15 17 17 19 19 17 17 16 total ¢ individuals 173 361 256 577 242 330 324 279 260 175 average size (in) 6.32 4.91 5.91 5.48 5.76 5.36 5.46 5.11 5.31 5.29 27 The only species showing any evidence of a seasonal trend at this study site were spotted goatfish and possibly parrotfish. As with the Reef Bay site, spotted goatfish show a peak in September with many being relatively small (2-5 inches). Parrotfish do show a peak in July and August although this was not due to an increase in number of juveniles. Many species at this site occur infrequently and sporadically, providing no evidence for seasonality. Total number of species shows a peak in August and September but this is probably due to a coincident occurrence of some of the species normally having a sporadic or infrequent occurrence. Backreef-—Rb On the east side of Fish Bay is a fringing reef (Figure 5). Periodic storms have created an emergent boulder ramparts composed primarily of old broken plates of Acropora palmata. This emergent reef crest has created a relatively protected, shallow backreef lagoon with colonies of Montastrea annularis, Porites porites and areas of Thalassia testudinum. The submerged portions of the boulder ramparts contain numerous spaces to serve as refuge for fish. Eleven monthly samples were made (Table 8) in this backreef lagoon from January 1985 to January 1986. Only two censuses were done each month as the primary fish habitat is very limited. A total of 18 species of commercially important fish were observed in this backreef during this period with mean of 11.4 (sd=1.3) species seen on each sample date. A mean of 116 (sd=13.3) individual fish were seen on each sample date. Mean average fish size for the entire period was 4.88 (sd=.24) inches. Of the 18 observed species, eight species were present in eight or more samples (75%) and seven species were present in every sample. The most notable thing about this site igs the large, resident school of schoolmaster snapper. Only two species show any observable indication of a seasonal trend in abundance. French grunt have a definite peak in September/October and squirrelfish appear to be most abundant in July to September. Although the average size for the schoolmaster seen was approximately 6.5 inches, the abundance of very small surgeonfish, tang and parrotfish depressed the mean average size. General Conclusions One year of monitoring the fish assemblages in six locations around St. John allowed for Statistical analysis of differences in numbers of individuals and species among bays and among dates. 28 TABLE 8 Average number of fish per census per species for Fish Bay backreef (Rb) from January 1985 to January 1986. (Total # fish/# censuses). ei en ee en en ee ee ne ee en ee ae ee ee a ee ee a ee ee ee ee ee ee a ee ee oe re ee em eee eee me eee me ee oe nee me blue- striped grunt 1.5 1.0 2.0 2.5 1.5 2.0 french : grunt 7.0 4.5 3.5 7.0 2.0 2.5 7.0 21.0 13.0 9.5 11.5 tomtate 2.0 1.5 1.5 1.5 1.5 1.0 2.0 1.5 2.0 4.0 1.0 smali-~- mouth grunt 2.90 school master 13.0 14.0 19.0 14.5 24.5 13.5 17.5 13.0 12.0 15.5 10.0 yellow- tail snapper 4.0 1.5 2.0 1.0 1.0 2.0 1.0 25 mahogany snapper 3.5 1.0 1.0 25 Aes) blue tang 4.5 4.0 3.0 6.0 2.5 2.5 3.5 3.5 7.0 6.0 2.0 surgeon fish 7.5 10.0 14.5 6.0 11.5 19.0 10.0 13.0 8.0 9.0 12.0 yellow goatfish 5.5 1.5 3.5 1.0 25 spotted goatfish 5 2.0 25 Po) 5 porgies «5 . parrotfish 4.0 10.0 13.0 9.5 12.0 8.5 10.5 13.0 6.0 8.0 10.0 trunkfish 5 a) 25 barracuda 5 oo) 1.5 A) -5 squirrel fish 25 3.0 1.5 2.5 2.5 5.5 4.0 5.0 2.5 2.0 1.5 mojarra 5 1.0 1.0 1.5 5 1.5 5 29 Table 8 (Continued) Average number of fish per census per species for Fish Bay backreef (Rb) from January 1985 to : February 1986. (Total # fish/# censuses). ee ee om ae ie me cere cre ee em come i care me ete ee te a te ee me cr me ne eee ee rm mk ee ce eee ee em my se se me ate ont mm re i nt ome ee i ee Oe ee ee ee ee ee ee ee mr ee ee ce i es ee rere ee ee es ee ee ee ee mee ee ee err te mm sete ee ae i ant ae ne ee a ee ne ie ee we ee ee ee ee total # , species 12 12 9 12 9 13 12 13 1i 11 11 total # indivi- duals ~ 105 104 123 103 116 120 118 151 109 119 103 average size (in) 5.31 4.76 4.69 4.96 4.73 5.35 4.95 4.63 4.91 4.72 4.66 30 Significant differences were demonstrated in number of individuals and species per census among study sites (Table 9). Reef Bay, with a total of 34 species observed, has the highest number of individuals (KRUSKAL-WALLIS, H=82.42, DF=2, P<.001) and species (KRUSKAL-WALLIS, H=48.92, DF=2, P<.001) for the three deeper water sites (Hawksnest SBpr, Reef Rf1l, Fish Rfl). This is probably related to the high relief of the site providing more abundant shelter. In comparison, Fish Bay yielded the same number of species but demonstrated a very low mean number of individuals observed per sample date. This is probably due to the low vertical relief of the site. Significant differences existed in number of individuals and species per census among sample dates for the three deep sites combined. Numbers of individuals differed significantly among dates (KRUSKAL-WALLIS, H=24.37, DF=11, P <.05) with larger means occurring from June to September. Number of species also differed significantly among dates (ANOVA, F=2.45, DF=11, P<.01) with no clear temporal pattern. Total number of species differed between shallow and deep habitats with upper forereef and backreef areas having the lowest number of species and the lower forereef and shallow bay patch reef having the greatest (Table 9). This is consistent with the results obtained from a fishery habitat mapping study (Boulon, 1985a). The shallow bay patch reef had the greatest number of species and this is probably related to the nature of patch reefs to concentrate species from surrounding less productive or low relief areas which do not provide adquate shelter. The only species demonstrating any evidence of a seasonal variation in numbers are yellow and spotted goatfish. The inshore upper forereef had a dramatic increase in schools of small yellow goatfish in September and October. The two lower forereef sites on the south shore had peaks in numbers of spotted goatfish in September. It appears that juvenile yellow goatfish aggregate in shallow water while juvenile spotted goatfish tend to stay in deeper water. No obvious variations are evident for other species. Small fluctuations which appeared to be differences were treated with caution for such fluctuations could be a product of observer biases (see Summary Conclusion). With the observed differences among bays and dates during the period of this study, the data provides a base to measure long-term changes in the fish assemblages at these sites. Future samples of replicated censuses conducted during 4 defined period should provide information on stability or decline of the fish assemblages. At present there are no comparable studies for other areas in the United States Virgin Islands which would enable statements to be made regarding state of these populations (i.e. are we looking at primarily juvenile, heavily overfished populations, etc.?) Commercial biostatistical sampling data for the U.S.V.I. has never been 31 TABLE 9. Sample statistics for each of the long-term reef fish monitoring sites on St. John, USVI.. Reef Hawksnest Bay Bay Fish Bay Southern Eastern Statistic SBpr Rfv Rfu Rfl Rfl Rb Total No. Species 36 22 19 34 34 18 X Species/ sample 21.4 11.5 11.6 21.0 16.5 11.4 (sd) (2.19) (2.27) (1.07) (2.40) (1.75) (1.34 XK Fish/sample| 428 388 363 657 298 116 (sd) (127) (89) (140) (185) (110) (13) 32 analyzed for size by species so comparisons cannot be made as to what is being taken out of the resource. Lobster - Panulirus argus and P. guttatus Methodology The same three watersheds were selected for long-term lobster population monitoring for the same reasons as with reef fish. The method used for monitoring the populations was simply to delineate an area to be studied and then thoroughly canvass it on a monthly basis. All ledges, crevices, and holes were carefully examined and all spiny (Panulirus argus) and spotted (P. guttatus) lobsters were counted. For each lobster an estimate was made as to carapace size (measured from the ridge between the horns to the posterior edge of carapace). A flashlight was used to examine the tops and backs of the deeper caves. Spiny lobsters are usually easily seen because they generally are found on the floor of the caves. Spotted lobsters are more difficult to find because they seem to prefer the tops of the caves. Due also to their smaller size, it is very likely that their abundance is underestimated. Capture of the lobsters for determination of sex and reproductive state was not performed due to the potential for injury or trauma to the lobster. Underwater maps were drawn of the study areas (Appendix Ia and Ib) and locations of lobster were marked on mylar overlays. By comparing monthly surveys as to size and location, some idea of residency can be determined. Reef Bay The lobster monitoring site at Reef Bay was located within the reef fish monitoring site (Figure 4). The study area was located on the seaward side of the fringing reef and includes the 50m coral monitoring site (Rogers and Zullo, 1986) (Appendix Ia) plus an additional 100m section of reef contiguous to and west of the 50m coral monitoring site. The study area is approximately 15m wide from the bottom of the reef at llm to approximately 3m in depth. The total area monitored was approximately 2250m . This site is exposed to the predominant wind and waves from the south and southeast and is frequently rough. Nine monthly samples were made at this site from April 1985 to February 1986 (Table 10). Numbers of spiny lobster found during this period ranged from zero to four per sample with all being less than 3.5 inches in carapace length and all being found in the 100m extended portion of the study area. No spiny lobster (Panulirus argus) were found on four of the sample dates. Numbers of spotted lobster (P. guttatus) found during this period ranged rn from zero to 10 per sampling date. Seventy-four percent (74%) of 33 TABLE 10. Numbers of spiny and spotted lobster by two size classes per sample date for two long-term monitor- ing sites, St. John, USVI. Dashes indicate no data available. 1985 1986 Apr May Jun Jul Aug Sep Oct -Nov Dec Jan Feb Spiny (>3.5") 0 0 0 0 0 0 0 - 0 - 0 Reef (<3.5") 0 0 0 2 1 4 2 - 1 - 0 Bay Spotted (>2") 0 0 1 0 2 2 7 - 6 - 5 (<2") 0 1 0 1 8) 0 0 - 4 - 2 Sea + conditions: 2 2 1 1 1 1 1 3 1 3 1 Visibility: 15' 15" 20* 30 30' 30' 20' - 30° - 30° Spiny (>3.5") 0 0 0 3 5 2 1 - 1 2 3 Fish (<3.5") 2* 0 1 5 2 6 0 ~ 1 10 1 Bay Spotted (>2") 0 0 0 1 2 3 2 = 2 5 4 (<2") 0 0 0 0 1 1 2 - 1 3 0 Sea + Conditions: 2 2 2 1 1 1 2 3 2 1 1 Visibility: 15° 20' 20 60 30' 40! 20° - 20 30' 20! + 1 - calm (waves <2') 2 - rough (waves 2'-4') 3 - very rough (waves >4') * Both were molts 34 the spotted lobsters found had carapace sizes greater than or equal to two inches, a size chosen by the author as a possible size representing maturity as the size range observed was 1.5 to 3 inches. Only one sample contained no spotted lobsters. During the study period, there appears to be some indication of seasonality of abundance for both species (Figure 6). Spiny lobsters were not seen for the first three months of the study. Their numbers increased to a peak in September and then decreased to zero again in February 1986. Spotted lobster showed a gradual increase in numbers from zero at the beginning of the study to a peak in December and then an apparent decrease after that. Caution should be exercised in interpretation of the observed trends due to the small sample size and the monthly gaps in the data set at the end of the study. Fish Bay The lobster monitoring site at Fish Bay was located within the reef fish monitoring site (Figure 5). The study area is located in the lower forereef spur system where many undercuts and coral overhangs occur along the interfaces between the spurs and the sand separating them. Due to the topography of this reef system (see Appendix Ib), the boundaries do not form a simple geometric shape resulting in difficult areal computation... A rough estimate of area within the boundaries is approximately 1600m. Ten monthly samples were made at this site from April 1985 to February 1986 (Table 10). Numbers of spiny lobster found during this period ranged from zero to twelve per sample date with 40% being 3.5 inches or larger in carapace length. No live spiny lobsters were found on two occasions although two molts were found on one of these occasions. Numbers of spotted lobster found during this period ranged from zero to eight with 70% having carapace sizes greater than or equal to two inches. Three samples contained no spotted lobsters. During the study period, there appears to be some indication of seasonality of abundance for both species of lobsters (Figure 6). For spiny lobsters there appear to be two peaks in abundance, one in the summer as was seen at Reef Bay, and another one in the winter, which was not observed at Reef Bay. Spotted lobsters show a seasonal trend very similar to that observed at Reef Bay. None were observed at the start of the study and numbers then increased to a peak in January and dropped off rapidly after that. Hawknest Bay The shallow bay patch reef in Hawksnest Bay was selected as a long-term monitoring site for lobster due to its location in the bay and the presence of suitable lobster habitat. The reef was surveyed monthly along its forereef side only as the rest of 35 15 Reef Bay 10- .° y . ] / 59 / / / af-d . <. ae aoe ~~” a . fe t t T T T T T T nF i C - 2 Spiny ° ol ~-~~--Spotted 6 15 2 Fish Bay 105 ie q L J F 1986 1985 ) Figure 6. Numbers of spiny and spotted lobster per sample date for two long-term mo- nitoring sites, St. John, USVI. Dotted lines indicate months where no sample was obtained. 36 the reef provides no significant habitat for lobsters. Inall cases these surveys were conducted on the same date as fish censuses. Eleven visits were made to this reef during the study period. Only one spiny lobster (carapace length approximately five inches) was observed on the reef (August '85). No spotted lobster was ever observed on the reef. General Surveys During the months of July and August 1985, nine additional sites around St. John were surveyed for lobster abundance (Figure 7). Sites were surveyed either using a measuring tape or by swimming an area and estimating the size. Minimum estimated area is indicated by a plus sign in Table 11 (e.g. 1000m +). Spotted lobsters were very common in all general surveys carried out in Reef Bay. Many areas containing good lobster habitat (Ram Head, western Hawksnest Bay and Western Haulover Bay) were surprisingly depauperate of lobsters. No juvenile lobsters were observed in the mangroves in Hurricane Hole. Three of the spiny lobsters observed in Mary's Creek were beneath undercut portions of shallow Thalassia grass beds in the bay. All three were from 1.5 to 2 inches in total body length. Observations based on general surveys east and west of the long-term study site in Fish Bay demonstrated that the selected monitoring site was the optimum (or at least preferred) lobster habitat. General Conclusions Although there is some evidence of seasonal variations in abundance for both spiny and spotted lobster at Fish Bay and Reef Bay, another factor became evident during the study, which may influence the observed differences. Abundance of observed lobsters appears to be affected by sea conditions. Table 10 shows sea condition and visibility for each survey date. The presence of a swell or surge of sufficient magnitude to cause sediment suspension and movement causes visibility to decrease. The lower number of lobsters observed under these conditions may be due to lobsters becoming more difficult to observe or lobsters moving deep into caves or into deeper, more protected water. A combination of the first two possibilities seems more likely as movement into deeper water would not be a rapid process, would be very energy intensive, and could be necessary frequently depending on the frequency of swells. Although no fishermen were observed at either of these sites during the study period, it is known that recreational fishermen (including sport divers) and some St. Thomas commercial fishermen do dive here and take lobster. Many people have mentioned that these areas are good lobstering spots which would indicate general knowledge. Interpretation of any results from these areas must therefore acknowledge the potential for harvest. 37 “TAS Suyor *saueu UOFIBIOT AOZ TT aTqeL 0} zajay © skaAins 1a3ysqoT [ersues Fo uot zev0T “yf aan38Ty 18° 20° =z 0,99 38 TABLE 11. Results of general lobster survey around St. John, USVI, during the summer of 1985. Refer to Figure 7 for locations. Location Date Approximate Numbers by Carapace Size area Spiny Spotted surveyed $35". _ 23250. $20.22" 1. Western Reef Bay 7/1/85 300n¢ 1 0 1 8 2. Eastern Reef Bay 7/1/85 1900m2 0 1 0 3 (White Cliffs) 3. Eastern Reef Bay 7/1/85 1900m? 0 0 1 4 (west of White Cliffs) 4. West Ram Head 7/12/85 500m2 0 0 0 0 5. Hurricane Hole 7/17/85 500m 0 0 0 0 (Mangroves) 6. Mary's Creek 7/25/85 500m? 4 0 0 0 (mangroves/grass beds) 7. Fish Bay - 7/31/85 500m2 0 1 2 0 (west & east of study area) 8. Hawksenest Bay 7/27/85 1000m2 2 0 0 ) (western shore) 9. Haulover Bay 8/6/85 1000m2 1 0 0 1 39 The three sites surveyed appear to have different potentials for lobster presence and abundance. The Hawksnest Bay site has the least potential due to limited habitat coupled with its location in a deep embayment (reduced circulation lowers recruitment and food supply). Although the largest lobster of the entire study was seen here, large lobsters may be very mobile and are probably transient. Fish Bay appears to have the best lobster habitat of the three long-term monitoring sites. It has good water circulation, and many good refuges for lobster. This site had significantly more spiny lobster greater than 3.5 inches in carapace length than Reef Bay (Mann-Whitney U=76.5, P=.05). No significant differences were observed in total numbers of spiny lobster or spotted lobster among Fish and Reef Bays. Spotted lobster may be more abundant than observed in this study. They are difficult to observe because they are usually on the roofs of caves and their smaller size allows them to be cryptically hidden in the smaller caves and crevices in a reef system. They are more cryptic than spiny lobsters. Fisherman generally do not.take them since they are small and there is no market for them. These factors, combined with their total protection in park waters, probably makes them more abundant than spiny lobsters. None of the spiny lobsters observed were long-term residents of one particular hole. In Fish Bay, where actual locations of lobster sightings were recorded, no single spiny lobster was observed for more than two months in the same hole. No single hole had spiny lobsters present in it for more than a three-month period. Spotted lobster appear to be more resident. Residency could only be documented with a tagging study. Conch - Strombus gigas Methodology Five sites were originally selected for long-term monitoring of queen conch(Strombus gigas) populations. These include Reef Bay, Outer Fish Bay, Inner Fish Bay, Hawksnest Bay and the small bay east of Leinster Bay which will be referred to from now on as Threadneedle Bay (it is bounded by Leinster Point to the west and Threadneedle Point to the east) (Figure 1). Visual swimming strip transects were used to estimate conch densities and determine abundance and adult to juvenile ratios. A one~hundred meter long, fiberglass tape measure, weighted at both ends, was laid out on the bottom. A diver then swam the transect line, counting all conch within 2m of each side of the line. Conch were recorded as adult or juvenile, based on the 40 presence or absence, respectively, of a flared lip. Number of strip transects varied between sites, depending on size and nature of the site, but the same number of transects were made on each sample date at each site. SCUBA was used at deeper sites (>3m) or where visibility is such that repeated free diving would cause inaccuracies in the counting of conch. Reef Bay Seaward of the fringing reef along the west side of Reef Bay is a rather extensive seagrass bed (Figure 4). The grassbed is composed of sparse to moderate density Syringodium filiforme and appears to be good habitat for conch. However, this area was spot-checked a number of times during the entire study period and- not a single queen conch (Strombus gigas) was observed. As queen conch tend to aggregate near the sand-grass interface, this was checked nearly every time fish surveys were completed at this study site. On several occasions forays were made up to 20m into the grassbed to determine if conch were present in the interior parts of the grassbed. Hawksnest Bay Hawksnest Bay has been reported to have large areas of dense seagrasses within the bay (Kumpf and Randall, 1971; E. Gibney, pers. comm.). Although these areas are still reported to exist, the density of seagrasses within these areas is reported to be low to moderate (Beets, et al., 1985) and very much reduced, presumably due to heavy anchoring in the area (E. Gibney, pers. comm.). In both April and August of 1985 large portions of the bay were surveyed by swimming and towing. No conch except for a few West Indian fighting conch (Strombus pugilis) were observed. The grassbed to the east of the shallow bay patch reef was spot— checked several times during the entire study period in conjunction with fish surveys at this site. No queen conch were ever seen at this site. Fish Bay Inner Fish Bay The inner part of Fish Bay is a shallow seagrass bed of moderate to dense Thalassia testudinum (Figure 5). This bay is reported to have had large populations of juvenile conch (no flared lip). Unfortunately, harvesting of these juvenile conch has severely diminished the numbers. Piles of empty juvenile shells in places along the shoreline yield evidence of the harvesting. In the middle of the bay is a large mooring buoy that has been unused for at least two years. This mooring was used as the apex for two 100m long by four meter wide strip transects. These Al two transects yielded 8002 of area surveyed per sample date. Eleven monthly samples were made from March 1985 to February 1986 (Table 12). While numbers of both adult and juvenile conch were very low, there does appear to be a trend during the study period (Figure 8, top). Both adults and juveniles peaked in abundance in late Spring and then declined through the rest of the study period. Juveniles were more abundant than adults throughout the study period. Outer Fish Bay Seaward of the lower forereef described in previous sections there is a seagrass bed (lim deep) that is composed of moderate to dense Syringodium (Figure 5). This seagrass bed parallels the shoreline in this area and is at least 100m wide. Seaward, this grass bed grades into an algal plain. To the east, the grass bed extends around Cocoloba Cay and into Reef Bay. The grass bed to the east of Cocoloba Cay was surveyed in September 1985 and found to have a lower density of conch than the study area selected just seaward of the lower forereef in Fish Bay. Four parallel 100m by four meter strip transects were traversed approximately 10m apart from each other on each sample date. The four transects were made in the same general location on each sample date. These yielded 1600m of area surveyed per sample date. Ten monthly samples were made from February 1985 to January 1986 (Table 12). Rough seas and poor visibility prevented missing samples from being taken. Throughout the study period, numbers of juvenile conch remained very low. Numbers of adult conch exhibited a very distinct seasonal variation with a peak in the winter and a low during the summer (Figure 8, middle). Summer is the reproductive season with numbers of conch observed copulating only in July and laying egg masses in August. In general, conch in this grass bed were associated with the grass/sand "blowouts" in the grass bed. Conch were not extremely common in the interior dense seagrass areas, except for the last sample which also had the greatest number of conch observed during the study period. Numbers of adult milk conch (Strombus a greater abundance of macroalgae occurs. Threadneedle Bay To the east of Leinster Bay on the north shore of St. John, there is a small shallow bay located between Leinster Point and Threadneedle Point (Figure 9). The seagrass bed parallels the shoreline and is bounded inshore by a fringing reef and offshore by sand grading into a deep water algal plain and rubble botton. The seagrass bed is composed of moderate to dense Thalassia and is approximately 300m long and 30m wide. Two 100m strip transects were made at this site on each sample date. The transects were started at the approximate center of the grass bed 42 TABLE 12. Numbers of adult and Juvenile conch per sampling date for three long-term monitoring sites, St. John, USVI. Dashes indicate that no sample was taken. Months Inner Fish Bay Outer Fish Bay Threadneedle. Bay (800m2) (1600m2) (800m2) *N/A 4N/J D N/A N/J D N/A N/J D Feb. (1985) - - - 208 2 -13 ) 1 -001 Mar. 0 0 0 198 0 ~12 0 0 0 Apr. 6 4 ~O1 127 3 08 1 10 ~O1 May 7 - - - ~ - 8 26 =. 04 June 2 13 02 102 5 07 2 27 04 July 3 5 -O1 71 6 05 4 1i 02 Aug. 1 3 -004 88 7 -06 0 10 -O1 Sept. 0 3 .005 120 4 -08 0 3 ~004 Oct. (0) 5 006 147 7 -10 1 21 03 Nov. 0 2 .003 131 7 -09 1 22 03 Dec. i¢) 2 003 - - ~ 1 0 -001 Jan. 1 3 -005 282 1 18 - - - Feb.(1986) 0 2 003 ~ ~ ~ 136 401+ 67 x 1.18 3.82 147.4 4.2 12.8 14.3 sd 1.88 3.37 64.3 2.62 38.86 12.9 *N/A = Number of Adults +N/J = Number of Juveniles D = Density (Conch/m2) 43 204 Inner Fish Bay 10- . \ . \ SS oo f8 wey Nene oe mo” “ Oy, ioe 77 — 0 t T T T T tT t t << 300% ° Outer Fish Bay , 200 © 7 o 5 4 € ° ; Oo : r) .. 2 ve 1004 , a Lana Ge we a Gee ee Oe ee gan ae Oa me wees ws . a 0 pe . 7 " ; T T T ‘ 401+ 30% Threadneedie Bay Feb. 4 WO ~ 136 data \ ‘ 4 Ly Li F M A M J J A Ss () N D J F 1985 1986 Figure 8. Numbers of adult and juvenile conch for three long-term monitoring sites on St. John, USVI. Arrow indicates date of first sample. Solid lines represent adults, dashed lines represent juveniles and dotted lines indicate months where no sample was obtained. 44 Marine Benthic Communities St. John, USVI 0 100 200 300 be | Scale in Meters Source: Aerial Photographs. NO S.1983 Wateriemon Cay Threadneedle Bay a bo. a. coat —_ **needle Pt. Vn Leinster Bay Salt Pond Figure 9. Threadneedle Bay, St. John, USVI, showing location of study site for long-term monitoring of conch population. *K denotes study area. See Table 3 for acronyms. and run 100m in each direction (east and west) approximately 10m in from the shoreward edge of the grass bed to yield 800m2 to area surveyed per sample. Twelve monthly samples were obtained at this site during the period from February 1985 to February 1986 (Table 12). Few conch were actually observed in this bay during all but the last month of the study. The majority of conch counted were juveniles. During the first eleven samples, numbers fluctuated considerably yielding no visible seasonal trends (Figure 8, bottom). There are two peaks which coincide roughly with the two peaks observed at the Inner Fish Bay site. Abundance of adult conch showed a similar pattern as well to the adult conch observed at the Inner Fish Bay site. On the last sample of the study period, however, the populations of both adult and juvenile conch increased tenfold. One hundred and thirty six adults were observed, of which over 90 percent were old, heavily eroded, thick-lipped "bullet" conch. The juveniles were mostly in the seven to twelve centimeter range and covered the bottom in large, dense patches. General Surveys General surveys for distribution of conch populations around St. John were conducted in two ways. The first was a repeat of a series of conch tows that were made in 1981 (Wood and Olsen, 1983). The second was a series of spot surveys in sites where conch habitat was known to exist or conch were known to have been found in the past. - Nine conch tows were made attempting to duplicate as closely as possible, through bearings and distances, the exact locations and lengths of tows made by Wood and Olsen (1983) (Figure 10). Tows were made using a diving sled (pictured in Kumpf and Randall, 1971) towed by a boat. The sled was manipulated by the diver in such a way that it was maintained close enough to the bottom so that all conch could be counted within a swath approximately four meters wide. Numbers of conch observed in 1985 were not significantly different from numbers observed in 1981 (Mann-Whitney U Test, U.05=60.0) (Table 13). In 1981 four of the nine tows had more conch than in 1985. All of these were within National Park boundaries. In 1985, two tows had more conch than in 1981. Both of these were outside National Park boundaries. Fourteen sites were spot-checked for conch (Figure 10, Table 14). This consisted of selecting a site and having divers swim over it noting bottom type and numbers of conch observed. Approximate area of surveys was estimated. Few to no juveniles were observed at sites which can be considered good juvenile habitat (shallow, protected, with ample food resources) (sites 1, 2, 5, 6, 7, 10, 11, 12 and 13). Very few adults were observed at sites which can be considered adequate or good adult habitat (sites 2, 3, 4, 8, 9, 12 and 14). Many harvested conch were observed at several sites. 46 ; *smoq Yyouod Auasaidar SLIqUNU PeTOAT) *‘sameu UoTRBIOT AOF QT pur CI SaTqeL oF Aazay “IASON Suyor ‘3g *(p) shaAINS [Te19Uas pur SMOJ YOUOD Jo. VOTIeIOT “OT san3tTy 18° 20° O-+ “2S +2 “00.9 47 TABLE 13. Results of conch tows duplicating those made in 1981 by Wood and Olsen (1983). Refer to Figure 10 for locations. Numbers in parentheses are densities in conch per square meter. Location Date Approximats Area No.Conch No.Conch —_Surveyed(m) olin 1981 1. Turner Bay 8/20/85 9000 34(.003) 25(.003) to Chocolate Hole 2. Rendezvous 8/20/85 7500 68(.009) 32(.004) Bay 3. Fish Bay 8/20/85 | 3000 8(.003) 26(.009) 4. Reef Bay 8/21/85 12500 34(.003) 45(.004) 5. Round Bay 8/21/85 . 2500 -0-(0) -0-(0) 6. West of 8/7/85 9600 61(.006) 167(.017) Haulover Bay 7. Leinster Bay/ 8/7/85 16500 59(.004) 128(.008) Mary's Point 8. Francis Bay 8/7/85 2100 -0-(0) -0-(0) 9. Cinnamon Bay 8/7/85 9200 -0-(0) -0-(0) to Trunk Bay 48 TABLE 14, Results of general conch surveys around St. John, USVI, during the summer of 1985. Refer to figure 10 for locations. Location Date Approx. Area Numbers Bottom Surveyed Observed Type* 1.Inner Fish Bay 7/2/85 Inside long- None Dense Th term transect to shore 2. Bay E. of 7/2/85 Seaward of 3 adults Moderate Leinster long-term Th study area 3. Eastern Reef 7/12/85 3000m 1 adult Moderate Bay Th/Sy 4. West Ram Head 7/12/85 1000m 6 old Sparse adults Sy 5. Otter Creek/ 7/17/85 1000m + None Algae on Water Creek sand 6. Borck Creek/ 7/17/85 1000m + None Moderate Popilleau Bay Th/Sy 7. Princess Bay 7/17/85 1000m + 61 Moderate harvested Th shells 8. Francis Bay 7/25/85 1000m + None Sparse (Northside) Sy/Hal 9. Whistling Cay 7/25/85 500m + None Sparse Sy 10. Mary's Creek 7/25/85 1000m + 2 Th and juveniles coral rubble 11. Reef Bay (Lg) 7/24/85 500m + 1 Dense Th juvenile 12. Bay E. of 8/6/85 500m + 15 adults Moderate Leinster (E. of L-T 5 juven- Th/Sy study area) iles 13. Bay E. of Brown 8/7/85 1000m + 3 Moderate Bay juveniles Th/ Sy 50 harv- ested shells 49 Table 14. (Continued) Results of general conch surveys around St. John, USVI during the summer of 1985. Refer Approx. Area Location Date Surveyed to Figure 10 for locations. Bottom Type* Numbers Observed 14. Western Reef Bay 9/3/85 500m*+ * Th - Thalassia testudinum Sy - Syringodium filiforme Hal - Halodule wright 50 Low density Moderate Sy General Conclusions The five long-term monitoring sites provide information on variation in conch abundances among locations around St. John. Hawksnest Bay, reported by residents to once have had an unquantified abundance of conch, now appears to have none. This may be due to past heavy harvesting coupled with past and present habitat degradation, primarly due to heavy anchoring impacts on the seagrass beds. Reef Bay presents a perplexing situation in that the grassbed surveyed appears to be adequate habitat for queen conch and yet no conch were ever observed there. Inner Fish Bay has adequate habitat for juvenile conch as evidenced by past observations (Boulon, 1985b). Present low numbers may be due to movement of the conch, harvest of the juveniles or inadequate recruitment. Piles of harvested juvenile shells on shore attest to the fact that harvest may occur there. Outer Fish Bay has the greatest abundance of conch observed anywhere in National Park waters. This area should probably be entirely closed to harvest of conch to protect it. A significant difference was observed among months for numbers of conch at this site (KRUSKAL-WALLIS, H=20473, DF=9, P<.05) with June to August -having the lowest number of conch. The seasonal trend observed here in 1985 is very similar to the trend observed in the four samples taken between March and June 1984 (Boulon, 1985b). A comparison of the two sets of samples for that period shows a decline in numbers to lowest abundance in July 1985. Observations on mating and egg laying during July and August suggests that a peak reproductive season exists. That this coincides with the low peak in numbers of inshore conch suggests that they may be migrating offshore into deeper water to mate and lay their eggs. This movement pattern would bring them into contact with other individuals in the population, provide greater protection from storm-induced sediment movement for the egg masses and/or enhance larval dispersal by ocean currents. This movement pattern is similar to that described by Hesse (1979) for the Bahamas but may occur somewhat earlier in the yeare She described the offshore migration in September and October. Coulston, et. al. (1985) describe an offshore movement of conch during the period from November to March at Salt River, St. Croix, U.S.V.I. This observation differs from ours and demonstrates the variation that apparently exists among sites. Coulston, et. al. (1985) reports a reproductive period from March to November in shallow water (50 to 70 feet). Threadneedle Bay does not appear to have a stable population of conch. The 1984 data showed evidence of rapid population changes going from 80% (165) adult and 20% (44) juvenile in one sample to 99% (253) juvenile and 1% (2) adult six weeks later (Boulon, 1985b). This year's data suggested that a low abundance of primarily juveniles inhabited the bay. 51 However, the last sample increased these numbers by tenfold. The older "bullet" conch observed in this sample may have moved inshore from deeper water (15-20m) populations known to exist immediately offshore of this site. The juveniles may be the year class from the 1984 reproductive season just becoming evident in the inshore habitat. Several investigators have estimated mean lengths for yearling conch to be from 7.6 to 10.8cm (Brownell, 1977; Berg, 1976). Prior to inshore movement and after settlement, these conch may have been dwelling offshore in the nearby deeper algal plain habitat, which may be advantageous in terms of growth and mortality (Appeldoorn and Ballantine, 1982). While a significant difference was observed among months at this site (KRUSKAL-WALLIS, H=18.709, DF=10, P<.05) no trends were evident. Disregarding the final sample at Threadneedle Bay, the population fluctuations observed in this bay and in inner Fish Bay are somewhat similar. These patterns may reflect the background levels of conch and their fluctuations in shallow, inshore waters. The results of the conch tows suggests that there has been no net difference in numbers of conch since 1981 in the deepwater areas. However, the comparison needs to be treated with caution due to possible differences in relocation of transects, observers, small sample size and differential harvest inshore and offshore. In general it appears that the abundance of deeper water conch may be presently stable. This is probably due to lower fishing pressure in these less accessible areas. These individuals may be responsible for maintaining the inshore abundances. Shallow water individuals appear to be in trouble as evidenced by the quantity of available habitat and the paucity of conch inhabiting it. The continued harvest of subadult conch will lead to the gradual decline and eventual near extirpation of local populations. Whelk - Cittarium pica Methodology The site selected for long-term monitoring of a whelk population within the Virgin Islands Biosphere Reserve is located along the north coast of St. John between Windswept Beach and Peter Bay (Figure 11). This section of coastline is bordered on its landward side by private property. The site was selected due to accessibility and known low levels of fishing pressure. The site is composed of good whelk habitat varying from solid bedrock sheets extending down into the water to scattered boulders with occasional tide pools. Seaward of this site is a narrow fringing reef. Benthic filamentous algae appeared to be plentiful as a food resource for the whelks. The study area 52 64° a0" Marine Benthic Communities St. John, USVI Q 100 200 300 t rn 1 j Scale in Meters Source: Aerial Photographs, NOS1982 Be Clanamon Cay oy 7 > SS on ene Sel , : ees Windswept Seach NEA. ty f OBg-ay Clay Cee — Trunk Bay Pater Bay a, ry ea— \ Ate —e 5 as a le ae Cinnamon Bay Ato. ar Littie Cinnamon 64°as' Figure 11. Windswept Beach, St. John, USVI, showing location of study site for long-term monitoring of whelk populations. fJydenotes study area. See Table 3 for acronyms. 53 included approximately 100m of coastline. Along this strip of coastline 10 randomly selected sampling sites were chosen. At each sampling site a one-meter wide strip transect was run perpendicular to the shoreline from above the high water mark to approximately one meter in depth seaward of the furthest offshore emergent boulders along the transect. All whelks were collected within this strip transect. Underwater portions of the transect were surveyed using mask and snorkle. After collection, all whelks were measured from tip of spire to distal edge of the lip and released at the capture site. Results Four quarterly samples were made during the study period with a mean of 33.5 (sd =6.28) whelks per strip transect (per meter of coastline) or a mean of 335 (sd =62.8) whelks per sample date (Table 15). There appears to be a greater number of whelks in the summer/early fall sampling than in the winter/spring samples. Although the number of whelks per sampling date varied, relative proportions of whelks in the larger size classes (greater than 2.5 cm) remained relatively stable for the study period (Table 15). The greatest difference among samples occurred in the first four size classes (Figure 12). The first sample had the greatest number of whelks in the 0 to .49 cm size class. The second sample had the peak in the .50 to .99 cm size class. In the third sample the peak was in the .50 to 1.49 cm size classes and by the fourth sample the peak was in the 1.0 to 1.99 em size classes. 54 Table 15. Numbers and relative abundance of whelk per size class on four sample dates at Windswept Beach, St. John, USVI. Density is expressed as number of whelk per meter of coastline. Size Class (cm) 4/22/85 7/11/85 9/4/85 12/16/85 a @ © © &@ @ © OOD UN W hob . * @ © @ @e #@ © © #@ @ © #@ #@ © © @ #@© @ @ & ry 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 | ed NOMoNMoNnouUNodMoNMNoOMoUNoMoMWodWed ee PR (.36) (.18) (.17) (.09) (.06) (.03) (.02) (.02) (.02) (.01) (.004) (0) (0) (.004) (0) (0) (.008) (.02) (.01)_ (0) (.004) (0) (.004) (0) i [oo] WHAM EN WHRN EF A 4 oo to -0- (.12) (.29) (.16) (.08) (.05) (.09) (.06) (.04) (.02) (.03) (.01) (.002) (.005) (.002) (.007) (.005) (0) (.005) (.02) (.005) (.007) (0) (0) (0) (.04) (.29) (.27) (.09) (.05) (.06) (.05) (.04) (.02) (.02) (.01) (.003) (.003) (.003) (.006) (.01) (0) (.006) (.01) (.008) (.006) (0) (.003) (0) U [oo] ! oS RP ENOW AN | AN RR H PON ' oO ' (.03) (.08) (.33) (.30) (.10) (.04) (.04) (.04) (.01) (0) (0) (.006) (.006) (.003) (.003) (.006) -0- (0) -O- (0) -O- (0) 2 (.006) -0- (0) 1 (.003) -0- (0) -0- (0) Total Density 236 23.6 409 40.9 357 35.7 339 33.9 Size Frequency 45 35 4-22-85 25 14 q re ee at 4- 37 pr 7-11-85 25 15 ee a 45 35 [}— 9-4- 85 25 as 45 a7 — 12-16-85 279 14 — Sh SINS AAR SN SO Se Sa SO STL nin el A IO SN ene ee eee eee Be Oe Se 4 8 12 16 20 24 Size Class Figure 12. Size frequency of wheliks collected at Wind- swept Beach, St. John, USVI, on four sam- pling occasions. X-axis numbers refer to size classes shown in Tablels5, 56 General Conclusions The data suggest a seasonal variation in numbers of whelks observed during the study period. A peak abundance in summer with lower numbers during the winter months may be a response to the increased frequency of high wave energy in the winter months. The whelk may move into more protected areas (deeper water or bays) or deeper into rock crevices where they are harder to observe. The most interesting aspect of these data is the presence of a very visible annual cohort. The April sample reveals the presence of post-recruits and the December sample shows yearlings in the 1.0 cm to 1.99 cm size class. This agrees well with Randall's (1964) estimate of growth rates of 1.06 mm per month for whelk ranging in size from 1.5mm to 8.2mm. Additionally, the size class distribution for juvenile whelk under 1.0 cm in the present study agrees very closely with the distribution observed by Randall (1964) in Europa Bay, St. John in 1959 and 1960. Her data for April, 1960 demonstrates the peak numbers of juveniles in the 0 to .5 cm size class as does this study. Randall (1964) also demonstrated that recruitment occurred in January. The majority of the individuals during the study were juveniles and subadults (<5cm). Most marine invertebrates have high reproductive output to compensate for the high mortality of larvae and juveniles. However, the middle range of adult size classes (5 to 8 cm) is represented by very low numbers. This is indicative of very high predation or mortality. Harvest mortality appears to be responsible for most mortality of adults in the Virgin Islands. There is a small number of large adults (>9cm) which has escaped predation by residing in the deeper portion of the transects. These large individuals may be responsible for the majority of the reproductive output in this area and for maintaining the present population. Summary Conclusions Management of a species or population depends on knowing the status of the species or population (present condition), where it is going (trends) and what is causing those trends (impacts). Management involves synthesizing this information and developing measures to mitigate negative impacts and reverse or stabilize downward trends. Obtaining this basic information involves development of a long-term monitoring technique which will best produce the necessary information for the species in question. The technique utilized depends on the size, mobility and general nature of the species as well as what information is being sought. Frequency of monitoring on the time frame of the 57 questions being asked. In general, where information on basic population size and fluctuations during one year is desired, monthly samples may be deemed adequate. The primary constraints on sampling frequency are financial resources and availability of qualified personnel. Some methods are very weather dependent and must be opportunistic in order to obtain adequate samples within the time frame of the study. Data produced over a single, one-year period will be useful for comparing to a similar unit of time in the future for determining long-term trends. Monitoring Recommendations When selecting or developing techniques for long-term monitoring of fish and invertebrate species, an attempt was made to use techniques that were simple, easily learned, relatively free from observer bias, did not require excessive equipment, and produced accurate quantitative data that could be used as a baseline data set for measuring changes in population levels or structure over a long period of time. The methods could easily be used in other Caribbean islands to produce comparable data sets. Although methods may be simple and easily taught, a basic recommendation is that, within any particular study, the same person(s) should conduct all the data collection to avoid individual observer bias. The random point, visual census technique used for assessing fish populations is good in that it is simple, easy to learn and accurate. A potential problem with this method arises from using different observers during the course of a study. When using a number of different observers, the data decrease in reliability. Various inconsistencies or biases due to observer differences can produce a high within-sample variability which can mask among-sample variation and obscure subtle trends or differences. Some of the inconsistencies which have to be considered include: 1. Misidentification of species ~ can be corrected if data is reviewed with thé observer immediately after collection, 2. Overlooking of juveniles of some species (parrotfish, surgeonfish) which lowers the number of individuals observed. and increases average size estimates. 3. Over or underestimation of size ~ usually consistent for each observer,:..and, 4. Lack of care in recording information (sizes or numbers of individtals). While the preliminary test of this method suggests that 58 80 percent of the species in an area are detected in the first four censuses (Figure 2), it is advisable to use at least ten censuses (for statistical reliability) within a habitat type unless the selected habitat is small and can be adequately covered with fewer censuses. Given the residence patterns of most reef fish species, monthly samples may be adequate to assess seasonal variation. The effects of fishing pressure (eg. fish traps on Hawksnest Bay SBpr) can also be detected with monthly samples, but more frequent sampling should yield more accurate analysis. The canvass method for surveying lobsters in an area is extremely simple and avoids random sampling error. The important consideration is extreme dedication to searching all possible refugia for lobsters. A flashlight is very useful in detecting lobsters in deep caves. Additionally, it is essential to initially map out the area to be surveyed. This enables a complete canvass of an area without missing or overlapping segments, as well as documenting the location and movement of lobsters within an area. Unfortunately, reproductive state of the lobsters is difficult to detect in a dimly lit cave so reproductive seasonality is difficult to obtain. Lobsters do appear to be somewhat sensitive to surge and sediment suspension. The sediment clouds washing in and out of their caves may affect them. This needs to be accounted for in any lobster survey. Lastly, it is important to determine the area surveyed in order to estimate densities. The strip transect methods used for conch and whelk are basic, simple and accurate. A possible improvement on the method might be to mark half transect widths (2m for conch, individuals who are on the edge of the strip transects) With conch, it is advisable to check all shells in which either movement or eyes protruding from the siphonal canal are not observed. With conch, if visibility is less than about 3m, the method is difficult and time consuming. The whelk survey method is impossible to conduct in high wave action. Wave wash makes it impossible to detect the very small (