Connectivity and Spatial Dynamics of a Nassau Grouper Metapopulation in the Bahamas: Fulfilling Urgent, Key Information Needs for Conservation  (Year 1 of 2) Project Number: CMRC-01-NRDE-04-02A Principle Investigators: Eggleston, D. B., C. P. Dahlgren, A. Eklund, C. L. Gerstner, and P. S. Rand Region(s): Exuma Sound, Bahamas, Little Cayman Ignorance of spatiotemporal scales of movement during larval and adult stages is a major impediment to understanding the population dynamics of marine organisms, and the successful application of marine protected areas (MPAs) to recovery and conservation measures for threatened species. Local, large-scale spawning aggregations of grouper and snapper are rapidly becoming extinct due to fishing pressure. Moreover, the size-at-age structure and sex ratios of many spawning aggregations are being negatively altered through fisheries selection. Identification of the locations, habitat and population characteristics of spawning aggregations (e.g., abundance, sex ratio, size-at-age) are clearly important in conserving remaining spawning aggregations and in the design of MPAs. Information on the status of the Nassau grouper (Epinephelus striatus) metapopulation in the Bahamas is urgently needed to help justify seasonal closures of wintertime spawning aggregations, for the spatial selection of no-take marine protected areas, and in providing information to International and U.S. agencies that are considering this species for endangered/threatened status. We propose to: 1) quantify habitat characteristics, as well as abundance, spatial and population characteristics (e.g., size-at-age, sex ratios) of Nassau grouper at spawning aggregation sites north and west of Lee Stocking Island; 2) quantify linkages between adult home range and grouper migration to spawning aggregations; and 3) begin to assess connections between spawning aggregations, larval transport trajectories, and subsequent settlement. During the full moon periods in December and January 2002-2004, we will quantify the locations of spawning aggregations using aerial reconnaissance of fishing vessels and trap floats (a proxy for likely spawning aggregations), historical information, and local guides. At each aggregation site, we will quantify the abundance, size and spatial structure of fish in aggregations using i) SCUBA, ii) a single frequency split-beam echo-sounder, iii) an underwater digital stereo-video system, and iv) a remotely operated vehicle (ROV) with video system. Population characteristics of fish associated with a specific aggregation site will be quantified by collecting size and weight information, as well otoliths and gonads from dock-side landings. Linkages between adult home range and spawning sites will be identified through a tag/recapture study, and through a feasibility study using archival, satellite pop-up tags, which have the potential to define unknown aggregation sites and the depths at which fish migrate. Finally, laboratory experiments will assess larval swimming capabilities of Nassau grouper and, when combined with ongoing work on Exuma Sound circulation and regional scale habitat mapping, will allow us to model larval transport trajectories and settlement sites. Nassau grouper, like many other species of Serranids, exhibit characteristics that make them particularly susceptible to overfishing such as slow growth to a large size, delayed reproduction, sex reversal, and aggregated spawning. Many spawning aggregations of Nassau grouper have become locally extinct, and remaining stocks show telltale signs of overfishing. Therefore, to aid U.S. efforts in “protecting, conserving, and restoring” depleted fisheries, it is essential that we study populations elsewhere. A relatively large population of Nassau grouper, combined with historic locations of spawning aggregations and a reasonable thorough understanding of recruitment dynamics of this species in the central Bahamas, provides an opportunity to gain a better understanding of essential spawning habitat. Such life history information can be used to properly locate MPAs in the U.S.   OBJECTIVES: Initially, the overall objectives were to: 1) quantify habitat characteristics, as well as abundance, spatial and population characteristics (e.g., size-at-age, sex ratios) of Nassau grouper (Epinephelus striatus) at “new” spawning aggregation (SPAG) sites north and west of Lee Stocking Island; and 2) quantify linkages between adult home range and grouper migration to spawning aggregations. We define “new” aggregation sites as those that have not been sampled quantitatively (i.e., other than several sites in southern Long Island). These initial objectives were modified, however, because the CMRC did not provide a research vessel to survey SPAGS in the Bahamas, as originally requested and approved in our proposal. We modified our objectives by collaborating with the Reef Environmental Education Foundation (REEF) and the Cayman Islands Government, Department of Environment (CDOE), to characterize a Nassau grouper SPAG off Little Cayman, BWI. This was necessary because our previous two research cruises in 2000 and 2002 to SPAGs off Long Island, Bahamas did not locate adequate numbers of Nassau grouper to quantitatively compare different techniques (acoustic, visual, 3-d video) for estimating spatial structure of SPAGs. Thus, our specific objectives at Little Cayman were to: (1) Quantify the spatial structure of spawning aggregations using a split-beam echo-sounder and 3-d underwater video system , both of which are capable of resolving 3-d position and size of individual fish in the water column; (2) Compare and contrast the survey results from 3-d video and acoustic echo-sounder surveys with visual estimates generated by REEF divers and D. Eggleston; (3) Observe and quantify spawning behavior using visual census, acoustic surveys and UW video; and (4) Quantify population characteristics such as size-at-age, sex ratios, and gonadal indices. Rather than miss surveying Nassau grouper SPAGS off Long Island, Bahamas during full moon periods in December 2002 and January 2003 due to the lack of a research vessel, Eggleston contracted divers from Stella Maris Resort, Long Island to visually survey two possible SPAG sites off the northern tip of Long Island that had not been adequately surveyed by our team in 2000 and 2002 (i.e., either a site was marked by aerial reconnaissance with high numbers of trap floats and not surveyed, or surveyed in January 2002 apparently after the primary aggregation period in December). Thus, objective (4) was to estimate the abundance of Nassau grouper at two “new” SPAG sites off the northern tip of Long Island, Bahamas. Our collaboration with REEF, CDOE, and Stella Maris represented an extremely cost-effective means of collecting valuable data on Nassau grouper SPAGs in the absence of a research vessel, and forged new collaborations on research and conservation of SPAGs in general and Nassau grouper in particular. Our last objective was (5) to assess the feasibility of using archival, satellite pop-up tags on Nassau grouper as a means to identify the location of SPAGS and likely migration routes and depths to such SPAGs. RESULTS: I. Abundance, spatial and population structure of a Nassau grouper SPAG off Little Cayman. (A) Background. - Surveys conducted the previous spawning season (January ’02) by the REEF and CODE teams revealed a large spawning aggregation of Nassau Grouper at the southwest corner of Little Cayman Island, Cayman Islands, British West Indies (L. Whaylen et al., REEF, in review; Figure 1). The spawning aggregation site is located in ~30 m of water on the edge of the Cayman Shelf where high relief spur and groove formations run perpendicular to the wall edge as it curves around the contour of the island. Currents can reach between 1-3 knots at the SPAG site. Approximately 5,200 Nassau Grouper were present at the spawning site in January 2002, and they exhibited courtship behavior and color change. Since there was an active fishery at the time, approximately 1,934 groupers were captured off this aggregation, with fishers and research divers vying for propriety to the aggregation site. Subsequently, the Cayman Islands Government enacted legislation to protect and conserve Nassau grouper SPAGs by: (1) closing all SPAGS to fishing in alternate years (e.g., closed January 1-Dec. 31 2003); (2) during those years when Nassau grouper can be taken from SPAGs a maximum of 12 fish per boat per day applies (hook and line only), (3) a size limit of > 12 inches, and (4) during every period from November-March, no trap may be located within one nautical mile of any designated grouper spawning area. Many fishermen blame the attention of outsiders on the closure of SPAGs, are acting hostile to foreign researchers, and feel betrayed by their own fishery department. Phillippe Bush (CDOE) hosted an informational forum for fishermen during the December 2002 full moon to explain the rationale and the rules for the closure, listening to their concerns and misconceptions, and answering their questions. In 2002, we were given permission by the CDOE (P. Bush) to survey the Nassau grouper SPAG off the southwest end of Little Cayman in December 2002 and January 2003 in the absence of fishing and in collaboration with CDOE and REEF. Teams from the National Marine Fisheries Service Southeast Fisheries Science Center (led by J. Schull in December 2002) and NC State University (led by D. Eggleston in January 2003) traveled to Little Cayman to document spawning activity of Nassau Grouper during the period surrounding the full moon (12/19/02 & 1/18/03). Because closing the SPAGs to fishing is so contentious and the debate so heated, our teams were asked to work within the recommendations of the CDOE Fishery Department and we complied by not engaging local fishermen or attempting to sample any landed fish. Note that we did not see any fish landed on Little Cayman. (B) Survey by NMFS in December 2002. - The research team was divided into two dive pairs. Each pair conducted Reef Visual Census (RVC) point counts (Bohnsack and Bannerot, 1986) at specific locations on the reef directly adjacent to the end of the Cayman Shelf, “The Wall”, or conducted focused “Predator Counts” during exploratory drift dives along the edge of the wall. These quantitative samples characterized the distribution and abundance of grouper populations, any spawning congeners, and baseline fish assemblage information. Dives were conduced throughout the day and often included early evening or dusk dives. Extensive photographs and video were taken to help characterize habitat and document behaviors during these dives. Forty two research dives were conducted during the five day research trip. Sixteen RVC point counts were conducted and eleven predator counts were conducted during drift dives. Almost all diving activity was done adjacent to the Cayman Shelf (The Wall). Nassau grouper landed by fishermen were to be weighed and measured, with the otoliths and spines kept for age and growth analysis and gonads extracted and preserved using a 10% Formalin solution to determine sex, reproductive stage, and fecundity. No Nassau grouper were landed in December 2002. Nassau Grouper are thought to reach maturity between 40-45 cm, which corresponds to 4 - 7 years of age (Sadovy and Eklund 1999). The Nassau Grouper observed along the wall both during point counts and predator searches ranged in size from 30 to 72 cm; however, no aggregations were observed. The Nassau groupers observed were generally solitary and were not exhibiting any courtship behavior or color changes. A few Nassau Groupers were observed with a very faint “white belly” color pattern, and two juvenile Nassau Groupers were observed exhibiting some sort of mock territoriality or courtship behavior, blanching white over the white sand as they interacted. Nassau grouper prefer water temperatures of about 26 deg. C for spawning to occur (Tucker et al 1993), however, during our surveys, water temperatures were consistently between 26.7 and 28.3 deg C., a further indicator of less-than-optimal spawning conditions. (C) Surveys by NCSU in January 2003. - During January 22-26, 2003 we used a vessel with a side-mounted split-beam echo-sounder linked to a computer/GPS navigation system to survey a Nassau grouper aggregation off the southwestern tip of Little Cayman (Figure 2) during dawn, mid-day, dusk and at night on 2 separate occasions. Concurrent with the acoustic measurements, we conducted in situ estimates of overall grouper abundance though visual counts and 3-d video recordings. Many of the in situ visual estimates of abundance were conducted simultaneously with the team from REEF. Thus, we should be able to compare two visual estimates of the size of the aggregation (REEF, D. Eggleston), with estimates from 3-d video (P. Rand), and the acoustic transducer (C. Taylor). We were unable to make extensive videotape recordings of spawning behavior because of extreme low light conditions at dusk and general lack of observed gamete release. (i) Visual observations of abundance, courtship and spawning behavior. The spawning aggregation (SPAG) of Nassau grouper was generally located along the wall and reef plateau at the southwest portion of Little Cayman Island. The teams from REEF/CDOE placed a 100 m transect line on the seafloor running southeast by northwest ~20m inshore of the wall in 30 m. depth. The full moon was January 18, and the SPAG was surveyed by NCSU during 1/20-24, 2003. The key observations were: ·During the day the distribution of Nassau grouper within the SPAG was clumped in a narrow band (10 m X 50 m) along the wall, and distributed somewhat uniformly on the adjunct reef plateau. Fish located along the bottom on the plateau were typically in a cleaning station with nearest neighbor distances of ~1.5 m. ·The “wall band” of Nassau grouper was generally located just seaward of the transect line along the wall, or located ~50 m east from the transect line. ·The number of fish ranged from 150-500 with lowest numbers generally observed at dawn. ·The SPAG was generally dominated dark phase fish (70-80%), followed by white belly (10%), bicolor (5-10%), and barred (5-10%) phases. ·Bicolor fish tended to “herd” or “nudge” dark phase fish during courtship, and appeared to chase dark phase fish during spawning rushes towards the surface. ·There was directed swimming by fish distributed on the plateau towards the wall just preceding sunset. ·The highest frequency of courtship and spawning behavior was observed at dusk on 1/23/03—no courtship or spawning behavior was observed at times other than dusk. ·Nassau grouper exhibited directed, schooling behavior just minutes prior to sunset with nearest neighbor distances reduced to ~0.5 m, development of separate pre-spawning “cones” of 80-200 fish rising towards the surface, followed by occasional outward radiating bursts of bicolor fish chasing dark phase fish that either resulted in gamete release or not. ·Pre-spawning cones were easily disturbed by divers and predators (barracuda). ·A total of 38 Nassau grouper (38 dark phase and 1 barred) were observed migrating away from the SPAG ~ 10m off-bottom along the wall at ~ 2 knots on 1/22/03. ·Other fish species appeared to be spawning at the same time as Nassau grouper, including smooth trunkfish (Lactophrys triqueter) and horse-eye jacks (Caranx latus). The SPAG also contained high abundances of yellowtail snapper (Ocyurus chrysurus), Bermuda chubs ((Kyphosus sectatrix), and Creole wrasse (Clepticus parrae). It was unclear if these other species were also spawning. (ii) 3-d Video surveys Methods We assembled an underwater stereo-video system for use in resolving three dimensional attributes of grouper aggregations. The system consisted of two underwater housings (Ikelite Model #6035.36) fitted with dome ports and mounted on opposite ends of a stainless steel bar. The video cameras were SONY Model TRV-11 (single 1.4 type CCD, 680,000 pixel resolution). The cameras were mounted to achieve an optical axis separation of 60 cm. The zoom lens was fixed at wide angle (3.3 mm focal length), and the cameras were set on auto-focus. Video records were archived on 60 min DV tape format. A single diver operated the camera system using handles placed between the two housings. The stereo-video system was calibrated with a quadrat consisting of 1/4" welded aluminum pipe. The quadrat dimensions were 50 cm X 50 cm X 30 cm. The pipe was welded in a regular grid pattern on each face of the quadrat such that the nodes of adjoining pipe were 10 cm apart. Images of the quadrat were captured on film. The quadrate was placed at distances ranging from 1 to 5 m distances (at 1 m intervals) from the camera assembly. The calibration was conducted in approximately 1 m water depth in a swimming pool located at the Southern Cross Club on Little Cayman. Because the two cameras were free running, it was necessary to synchronize them. Frame synchronization was achieved using an underwater laser pointer (Model MBSL, Class IIIA, max output <5mW, wavelength 635 nm) directed onto a light background. This was typically accomplished by a single diver. The diver operating the camera would point the camera assembly either at another diver or on the reef, and repeatedly illuminate an area with the laser pointer that would be recorded simultaneously by both cameras. To assure that we had proper frame synchronization for a particular pair of images captured during a dive, we relied on unique visual or auditory clues during playback (e.g. diver movements, taps on housing or sounds from regulator, unique fish behaviors). Preliminary results We filmed Nassau grouper aggregations on seven separate dives. We present a summary of the video data collected in Table 1. We present several stereo-paired video images to document some of the properties of the aggregation that were captured with our system. Figure 2 includes morning footage on 23 January 2003. During this period, fish were relatively close to the reef and exhibited polarized swimming aligned along the shelf break. At least 40 individual grouper are identifiable in each image. We found identifying the same individual in each frame relatively straightforward given the diversity of color phases present within the aggregation. This is critical to obtain accurate positions of individuals within the aggregation. We intend to digitize these positions as screen coordinates and convert them to real world coordinates to compute nearest neighbor distances and density measures. In addition, digitizing anterior and posterior points along the main axis of the fish will provide individual length data. Density and individual length determinations from our video sampling will then be compared to echo integrated densities and target strength measures from our acoustic surveys. Fish were sometimes encountered in looser, less structured aggregations. We encountered such an aggregation during the same dive above (morning of 24 Jan 2003, Figure 3). Individuals in this aggregation exhibited more milling behavior, and in several cases we documented courtship behavior, with bicolor males closely attending dark phase females. In most cases, the aggregation took the form of an extended band running parallel to the shelf break, elevated off the bottom, with individuals in a polarized orientation (Figure 4). (iii) Acoustic surveys Background and Objectives Recent advances in fisheries sonar technology has made it possible for portable equipment to be used on smaller bodies of water to assess fish populations in inland waters, estuaries and coastal ocean systems. Advantages of acoustic sampling include: 1) non-invasive method of sampling the fish community that is less affected by size and gear selectivity, 2) collection of spatially continuous data along a series of transects providing information on sub-meter to kilometer scales, 3) use of “split-beam” technology, which permits collection of position of fish targets in 3-dimensions, 4) rapid assessment of biomass and abundance through more expansive coverage of an aquatic system, 5) reduce the number of man-hours and equipment required to sample the populations using active and passive gear such as trawls and gill nets. While the technology permits determination of acoustic size of fish targets, identification of species still requires 1) supplemental sampling for species composition and verification of size frequency distributions or 2) prior knowledge of behavior and size distributions of resident species. Applications of fisheries acoustics to the assessment of reef species are very rare, primarily due to difficulties with, 1) species identification and verification, and 2) inability to resolve fish targets that are closely associated with bottom relief. Acoustics may be useful in situations where fishes form very large aggregations during spawning, such as has been observed in cod as well as grouper, snapper and their allies. Formation of very large aggregations (>1000 fish) makes visual censuses extremely difficult due to limitations in bottom time, especially at depths near 30-m. In such cases acoustics provides an advantage of increasing coverage of the survey by several fold. The objective of this component of the project was to take advantage of the known aggregation of Nassau grouper off Little Cayman Island (REEF 2003) to provide a more rigorous test of the application of sonar in assessing grouper aggregations. We also employed stereo-video cameras to validate Nassau grouper sizes observed using acoustics. Methods We used a 200-kHz HTI Model 241 split-beam echosounder (Hydroacoustic Technology Incorporated, Seattle, WA) coupled with a circular (6o nominal beam dimension) transducer. The transducer was mounted to a 1.2-m long towbody rigged from a 1.5-m boom attached mid-ship on the starboard side of a 9-m dive support vessel. Towbody depth was maintained at 0.5- to 1.5-m below the surface depending on sea conditions. Rigging of the towbody included a shock-dampening system that minimized the oscillations due to pitch and roll of the vessel. Vessel speed was about 2 m s-1. Data collection parameters were specified by the user and controlled using a laptop that was networked to the echosounder. Ping rate was 5 pulses s-1 and the pulse width was 0.18 ms during all transect runs. Maximum range of echo detection was set at 75 m, the maximum range allowed given ping rate and sound velocity. Target resolution was calculated based on pulse width and sound velocity and found to be approximately 0.1 m; however due to significant bottom relief, fish targets were not resolved from reefs at distances less than about 1 m. At the beginning of the cruise we conducted an in situ system calibration using a tungsten-carbide reference sphere of known target strength placed greater than 5-m from the transducer. Gain parameters were adjusted accordingly based on calibration results. Received acoustic signals were simultaneously adjusted for spreading loss by applying 40-logR and 20-logR time-varied gain for split-beam and echo-integration processing, respectively. The data were processed in real-time for split-beam and echo-integration (HTI DEP v. 3.54, HTI Seattle, WA) and stored as text files on a laptop computer for later data analyses. Acoustic data were post-processed using split-beam and echo-integration analyses. Split-beam analysis was used to determine acoustic size (target strength) of individual fish targets in decibels (dB). Algorithms were used to accumulate several consecutive echoes from individual fish to produce an average acoustic size and position within the water column (HTI Echoscape v. 2.11, HTI, Seattle, WA). Target strength is proportional to fish size, and using established equations for reef species encountered during previous studies (McClennan and Simmonds 1992, Ehrhardt and Deleveaux 1999), target strengths were converted to fish size and verified during diver surveys. Only fish targets between –50 and –25 dB were used for split-beam analysis, representing the range of fish sizes observed by divers. On numerous occasions, fish targets were densely packed making split-beam analysis difficult due to overlapping echoes. When targets overlap and individual echoes are not discernable, echo-integration was used to estimate density of fishes present. Echo-integration is based on the principle that the total sound energy returned from an ensonified volume of water is proportional to the fish density. When scaled to the average fish size observed (either using diver observations of clear echo traces), volumetric densities can be calculated. Surveys were conducted at a single site off Little Cayman Island (Figure 5) from 22-23 January and again on 26 January 2003. Surveys were conducted two times each during morning, afternoon and evening hours, to correspond with dive surveys at the same locations. Acoustic survey design was a grid of 8 to 10 parallel transects 0.3 to 0.5 km in length and spaced approximately 25-m apart (e.g., Figure 5). In general, transects ran nearly perpendicular to shore from the 25-m depth contour nearshore to >100-m offshore. A second survey design was employed during the evening of 23 January 2003. Eight transects, each ~300-m long, were surveyed parallel to the shelf-break. Immediately prior to or following each acoustic survey, dive surveys identified dominant species and sizes to validate species and sizes observed during acoustic surveys. Species validation has been proven to be vital in fisheries acoustic surveys, especially in situations when diverse fish species of similar (or even different) sizes can have target strengths that overlap with that of the target species, Nassau grouper (Eggleston et al. 2002). Results Overall performance No significant problems were encountered while conducting any of the surveys. There were, however, some periods when wind, current and waves made navigation somewhat difficult and the best attempts were made to maintain straight and parallel transect lines. The deployment of the transducer using the starboard mounted boom and shock-dampening system provided for far reduced transducer movement over the traditional hull-mounted orientation. Preliminary split-beam analysis All surveys resulted in positive identification of medium to large aggregations of fishes well within the sizes of Nassau grouper observed during dive surveys. In all cases, large targets observed by acoustical methods were verified by divers as being Nassau grouper. Dense aggregations resulted in numerous occasions where individual echoes were not discernable due to fish target overlap, or fish separated by less than the allowable echo resolution of 0.2-m. Statistics on target strength in most cases were limited to echoes that produced good traces, where each fish produced a minimum of 4 echoes in sequence and having a narrow range of target strength and produced good traces indicative of a single fish passing through the acoustic beam. Typically, these targets were located on the outer boundaries (either vertically or horizontally) of the aggregations. Usually 2 to 20 targets were successfully tracked for each aggregation during each sampling occasion. Individual fish sizes ranged from -45 – -26 dB. Using established conversion equations, these target sizes equate to Nassau grouper of approximately 60 – 90 cm TL (Figure 6). The established relationships between target strength and fish size was conducted using only 6 fish with little variation in sizes (Ehrhardt and Deleveaux 1999). Based on diver observation and preliminary analysis of video data, we feel that the relationship might be negatively biased, resulting in an underestimate of fish size. We plan to improve the robustness of the size-target strength relationship of Nassau grouper by combining the observations of the stereo-video surveys with the acoustic data (Spring 2003). Several targets were observed in close proximity to the bottom, especially during the daytime. Algorithms are being developed that will permit extraction of these targets from bottom echoes which will provide valuable information on spatial distribution of fishes over the diel. Preliminary echo-integration analysis In general, the spatial locations of aggregations were restricted to the shelf break on the southeast portion of the survey region (Figure 7). In most cases, these aggregations were well off the bottom and sometimes had high vertical extent, extending 10-m into the water column. This vertical position was confirmed with diver surveys. In many cases, aggregations were observed well outside the region typically observed by diver surveys. Highest densities (qualitatively assessed from echograms) were observed during the evening of 22 and 23 January 2003 at a position just south and east of the southern-most marker buoy (Figure 5). Another large aggregation was observed the morning of 26 January. The location was further up on the plateau of the shelf, east of the south marker buoy (Figure 5). Due to inclement weather, however, we were unable to dive on this aggregation and confirm the presence of Nassau grouper. Large target strengths and the size of the aggregation lead us to believe that these were Nassau grouper. Statistical models are being developed to produce robust estimates of density and abundance for each aggregation observed as well as determinations of spatial extent for each aggregation (Spring 2003). 2. Abundance of Nassau grouper at possible spawning aggregation sites off Long Island, Bahamas (A) Background During our research cruise to Long Island in December 2000, we used aerial reconnaissance to identify possible SPAG locations through the identification of relatively high clusters of fish trap floats. Two possible SPAGs were identified in this manner in December 2000 off the northern tip of Cape Santa Maria, Long Island; however, were unable to dive these sites because our efforts in 2000 were concentrated at SPAGs off the southern and middle portions of Long Island. During our research cruise to Long Island in late January 2002 we dove both potential SPAG sites off Cape Santa Maria (herein referred to as Cape Santa Maria North; CSMN: 23.43.660o N/75.21.330o W; and Cape Santa Maria South; CSMS: 23.43.374o N/75.18.600o W; Fig. 8). We did not observe any Nassau grouper at these sites in January 2002; however, several local fishermen and divemasters we spoke with during our cruise in 2002 indicated that Nassau grouper were “schooling” at these sites in December 2001. Thus, given that we did not have a research vessel for December 2002, Eggleston contracted divemasters at the Stella Maris resort near Cape Santa Maria to survey CSMN and CSMS on or as close as possible to the full moon in December 2002, and January/February 2003. (B) Results (i) December 2002. - Both CSMN and CSMS were surveyed on December 20, 2002, one day after the full moon. The CSMN site contained 800-1,000 aggregating Nasssau grouper, as well as aggregations of horse-eye jacks (350-400 fish), Bermuda chubs (400-500 fish), and Mutton snapper (Lutjnus analis; 75-100 fish). There were ~60-80 fish traps, each containing 4-8 Nassau grouper, and two boats fishing the aggregation. On the same date, the CSMS site contained only 100-150 Nassau grouper; however, there were 150-200 fish traps present, each containing 4-8 grouper. Moreover, there were ~40 boats fishing the aggregation, and local fishermen reported that they had harvested 1500-3500 pounds of Nassau grouper per boat per day during a ~ 7d period preceding and including the full moon (12/15-20/02). Given that a single 60 cm TL Nassau grouper weighs approximately 9 pounds (Sadovy and Eklund 1999), these estimates of harvest are likely exaggerated because a single boat could harvest at least 166 fish per day leading to a total harvest of over 39,840 fish in 6 d by the “fleet”!! Nevertheless, if we conservatively assume that fishermen can capture 100 fish per boat per day, and that 10 boats work a 6 d period, then 6,000 grouper could be removed in 6 d. It remains to be seen if the CSMS SPAG was exterminated by fishing in December 2002. (ii) January/February 2003. – During January 2003, one Nassau grouper was observed at CSMS and none at CSMN. There were ~ 40-50 Mutton snapper at CSMS. During February 2003, there were only 10 and 5 Nassau grouper at CSMN and CSMS, respectively. There were 40-50 and 15-20 Mutton snapper at CSMN and CSMS, respectively. Lastly, there were 250-300 and 25-30 Bermuda chub at CSMN and CSMS, respectively. Thus, highest concentrations of Nassau grouper, as well other potential spawning species, were observed off Long Island during the December full moon. 3. Feasibility study using archival, pop-up satellite tags. During 2002-03, we captured and tagged three Nassau grouper ranging in size from 58-71 cm TL with dummy satellite tags (tag casing and antenna without internal electronics, but of equal weight to the real tag; Figure 9) and placed them within in-ground seawater ponds at LSI containing concrete block shelters. The goal was to determine whether or not tags would be retained for at least 3 weeks despite the potential of being torn from the body due to sheltering behavior. All three fish retained their tags for at least 3 weeks (range 21-60 d). We plan to tag 1-2 more fish during the first part of 2003. Based on the positive results so far, we plan to tag four Nassau grouper with real satellite tags programmed to pop-up and relay location information on the full moon in December 2003. Once on the surface, the tags will drift for 42 d (average larval duration of Nassau grouper, D. Eggleston, unpubl. data) to provide information on possible larval trajectories from a given spawning location. PAPERS PRESENTED BASED ON 2002 WORK: Eggleston, D. 2003. “Overfishing hyper-aggregations of animals” NC State University, Raleigh, NC. MANUSCRIPTS AND PUBLICATIONS: A total of five manuscripts are planned once data analyses are complete (Eggleston et al.; Fox et al.; Eklund et al.; Taylor et al.; Rand et al.). We have used some of the information from this study (i.e., visual surveys of Long Island aggregations), in concert with the Bahamas Department of Fisheries and the IUCN committee on threatened and endangered species, to push for a pre-cautionary management approach for Nassau grouper through seasonal fishing closures during wintertime spawning periods. REFERENCES Bohnsack, J. and S. Bannerot. 1986. A stationary visual census technique for quantitatively assessing community structure of coral reef fishes. NOAA Tech. Rep., NMFS 41, 15. p. Ehrhardt, N. M. and V. Deleveaux. (1999). Report on the 1999 Nassau grouper stock assessment in the Bahamas. University of Miami, 38 p. Hughes, N.F. and L.H. Kelly. 1996. New techniques for 3-D video tracking of fish swimming movements in still or flowing water. Can. J. Fish. Aquat. Sci. 53:2473-2483. MacLennan, D.N. and E.J. Simmonds. 1992. Fisheries Acoustics. Chapman and Hall Fish and Fisheries Series 5, New York. Sadovy, Y. and A-M, Eklund. 199. Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the jewfish, E. itajara (Lichtenstein, 1822). U.S. Dept. Commer., NOAA Tech. Rep. NMFS 146, and FAO fisheries Synopsis 157, 65 p. Tucker, J. W. et al. 1993.Reproductive patterns of Cayman Islands Nassau grouper (Epinephelus striatus) populations. Bull. Mar. Sci. 52:961-969.

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