Connectivity and Spatial Dynamics of a Nassau Grouper Metapopulation in the Bahamas: Fulfilling Urgent, Key Information Needs for Conservation  (Year 2 of 2) Project Number: CMRC-01-NRDE-04-03C Principle Investigators: Eggleston, D. B., C. P. Dahlgren, A. Eklund, C. L. Gerstner, and P. S. Rand Region(s): Lee Stocking Island 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.   SEMI-ANNUAL REPORT Field Work to be complete December 2003 and January 2004 ANNUAL REPORT OBJECTIVES: 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; 2) quantify linkages between adult home range and grouper migration to spawning aggregations, and 3) characterization of population structure of Nassau grouper collected fro spawning aggregations. These objectives were to be accomplished through tag-recapture of reproductively mature Nassau grouper with archival pop-up satellite tags, and through research dive cruises to SPAGs. 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 somewhat because the CMRC did not provide a research vessel to survey SPAGS in the Bahamas, as originally requested and approved in our proposal. RESULTS: 1. Abundance, spatial and population structure of Nassau grouper SPAGs off Long Island & Andros, Bahamas (D. Eggleston, P. rand, C. Taylor) Rather than miss surveying Nassau grouper SPAGS in the Bahamas during full moon periods in December 2003 and January 2004 due to the lack of a research vessel, Eggleston contracted divers from Stella Maris Resort, Long Island to visually survey two SPAG sites off the northern tip of Long Island during December 2003, and then Eggleston surveyed these sites with the assistance of local divers during January 2004. A team from NC State University and CMRC/LSI surveyed Nassau grouper SPAGs off Andros during January 2004. (A) Long Island, Bahamas (Dave Eggleston (NCSU) plus divemasters from Stella Maris) - The dive team conducted Reef Visual Census (RVC) point counts (Bohnsack and Bannerot, 1986) at two SPAG sites off the northern tip of Long Island, Bahamas: 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. 1). During December 9, 2003, one day after the full moon, approximately 30 and 18 aggregating Nassau grouper were observed at Cape Santa Maria North and South, respectively. Local fishermen and divers indicated that fishing boats were fishing these sites beginning on December 1, 2003. During December 9, 2003 two fishing boats were observed fishing ~ 40 traps, as well as using hook and line at Cape Santa Maria North. During January 2004, only 18 and two Nassau grouper were observed at Cape Santa Maria North and South, respectively. One fish observed at CSMN was bicolor. Eggleston quantified habitat features at both sites during January, 2004. Both sites were located ~ 200 m from the shelf-break, which was not a wall but more sloping bottom. Each site consisted of a hardbottom “hump” that measured ~ 100m X 60 m, was 20-28 m deep, and surrounded by old spur and groove coral reefs that ran perpendicular with the shoreline and sloped from the hump to a depth of 33-35 m.. All grouper were observed resting in the spur and groove areas, similar to observations at Hells Gate, Long Island during 2000. (B) Andros, Bahamas (Chris Taylor (NCSU), Peter Rand (Wild Salmon Center), Erin Rechisky (CMRC), Matthew (Dive Master, Small Hope Bay Lodge), and Mike (Senior Dive Master, Small Hope Bay Lodge). The objectives for this survey were to se hydroacoustics, 3-D video, and visual surveys similar to our surveys at Little Cayman in 2003. This portion of the report is described in a cruise report format since this was our first sampling effort at Andros. 5 January Taylor and Rechisky arrived at Small Hope Bay lodge (SHB) and prepared for survey of High Cay aggregation site (Fig. 2) 6 January 1430h: On board SHB dive boat “Ralphy”. Taylor and Rechisky, along with Matthew (Dive Master, SHB) surveyed location according to landmarks on High Cay given by Mike (Senior Dive Master, SHB). Coordinates for this location are given in Table 1 and displayed on Figure 3. Bottom sloped from High Cay to 40-43 m at the shelf edge. From GPS waypoint, the divers swam south-southeast along the shelf edge for ~200m and returned to boat along 100-foot contour. Total search area was approximately 16,000 m2. Maximum dive depth was 35 m and total bottom time was 30 minutes. Location was desolate and lacked significant coral and bottom relief. Rechisky observed a single Nassau grouper, 30-35cm TL. Very few other species were observed. We were unable to conduct hydroacoustic survey from this boat. Figure 1. Nassau grouper spawning aggregations sites off Long Island, Bahamas. CSM = Cape Santa Maria North, CSMS = Cape Santa Maria South, HG = Hell’s Gate, LHN and LHS = Little Harbor north and south, respectively, and SP = South Point. 7 January 1430h: On board SHB dive boat “The Big Boat”. Taylor, Rechisky and Rand, along with Matthew surveyed location 500-m south of 6 January location (Table 1, Figure 3). From anchor, divers swam north along shelf edge to the end point of the previous days dive. Similar bottom relief and depth as 6 January. No grouper were observed. Other species included a single trunk fish and several queen angels. Total search area was 16,000 m2. Winds were increasing throughout the survey and resulted in seas that were too rough for hydroacoustics. 8 January No diving due to high winds and rough seas. We acquired coordinates of previous aggregation surveys conducted by Dr. Tim Turnbull in February 1999 (see Figure 3, Tim1 & Tim2). Tim 1: 24 38.761N 77 41.300 W, Tim 2: 24 36.793N 77 41.388W. Tim 1 was within 600-m of survey location on 7 January. Tim 2 was well south of survey and well outside the closure area and probably closer to Long Cay (Figs. 2 & 3) 9 January 1430h: Rand and Rechisky entered water at 80-m west of Tim 1 and swam in direction of shelf edge, then along shelf edge. Bottom was 43-47 m deep. Less than 100-m north-northwest, 24 Nassau grouper were observed, two (Rand) to several (Rechisky) were observed in bicolor color phase, remaining fish were “barred”. Fish were at 43 m depth very close to shelf edge. Fish were “milling around” and not oriented in any particular direction. Divers continued to swim 100-m NNW but did not observe any more grouper. Other species included horse-eyed jacks (several dozen), Bermuda chub, a large black grouper and a large green sea turtle. Bottom had significant coral and sponge cover and relief. Grouper were observed at a large spur of reef at shelf edge. Approximately 8,000 m2 of area was searched. Total bottom time was 31 minutes at a maximum depth of 32 m. A total of 15-20 minutes of stereo-video footage was collected. 1630h: Rand and Rechisky swam a path SSE from anchor. No fish were observed. The shelf edge started to turn southwest just south of anchor point. According to satellite images, High Cay appears to be located on a promontory on the east side of Andros Island (Figure 2). Taylor and Mike entered the water and swam the same path as Rand and Rechisky at 1430h. Taylor observed 20-24 fish at same location as found by Rand and Rechisky and did not proceed further than fish location. Mike proceeded to an undercut in the wall and a small cave at 195-feet depth (Figure 2, “Cave”). Several dozen old diving spears were observed in addition to 2 sharks and 30-40 Nassau grouper in a mix of bicolor and barred color phase. Fish were milling around, not oriented in a particular direction and in very close proximity to the wall with some within the small cave. Approximately 15 minutes of stereo-video footage was collected. Due to user error, hydroacoustic equipment was not used. 10 January Rand, Rechisky and Taylor departed Small Hope Bay lodge. Table 1. Date and location of dive surveys at High Cay. Date/Time Lat/Long Area Searched Grouper Observed 6 January 1430h 24.65388 -77.6927 ~16,000 1 7 January 1430h 24.65067 -77.6908 ~16,000 None 9 January 1430h 1630h 24.64598 -77.6888 ~8,000 20-24 at 130-feet, 2 bicolor30-40 at 195 feet, several bicolor Figure 2. (Left) Map of Andros Island with approximate location of Small Hope Bay Lodge and High Cay. (Right) Map of east of Andros Island highlighting High Cay and Long Cay. Grey-scale represents elevation with the location of High Cay and Long Cay clearly on the shelf-edge. Figure 3. Map of Closed Area and locations of dive surveys (noted by date), location of cave at 195 feet depth (“cave”), and positions of surveys conducted by Dr. Tim Turnbull in February 1999 (Tim1 and Tim2). Our data so far strongly suggests that December is the primary month of Nassau grouper spawning in the southern Bahamas, whereas January and February are the peak months in the Cayman Islands (see final report for 2002-3003). Although we did not document large aggregations of Nassau grouper near Andros, we now have the coordinates for the SPAG there, as well as habitat characteristics. 2. Quantify linkages between adult home range and grouper migration to spawning aggregations (D. Eggleston & C. Dahlgren) During October-November 2003 a total of four archival, pop-up satellite tags were constructed to be attached to reproductively mature Nassau grouper and programmed to pop-up to the water surface on the full moon in December 2003 (12/8) at a time to coincide with satellite passage over the southeastern Bahamas. The tags were also programmed to record pressure and water temperature to help indicate water depths used by migrating fish. The tags were also programmed so that after they broke the water surface, they would relay location information 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. During November 9-14, 2003 we used fish traps within the vicinity of LSI to capture relatively large (60-70 cm TL), reproductively mature Nassau grouper for tagging with pop-up satellite tags. Strong winds and high seas prevented successful capture of Nassau grouper of the proper size for tagging, so the tags were sent back to the manufacturer and reprogrammed to pop-up on the full moon of January, 2004 (1/7/04). During December 12-16, 2003 we again attempted to capture Nassau grouper for tagging, and were unsuccessful due to high seas. The current plan is to reprogram the tags and repeat this procedure, if weather allows, during November 2004 with CMRC/PIMS seed funds. 3. Characterize population structure of Nassau grouper in spawning aggregations (A-M. Eklund & J. Schull, NOAA/NMFS) During 2003-04 we continued to process otoliths and gonadal samples of Nassau grouper collected from spawning aggregations off Long Island, Bahamas during 2000 and 2002. The major fish house on Long Island, Bahamas was located in Clarencetown. The majority of fish landed at Clarencetown were harvested from the Hells gate SPAG, located just east of Clarencetown (see final report for 2000-2001 and 2001-2002). The length-frequency of Nassau grouper landed at Clarencetown was dominated by fish ranging from 58-70 cm TL (Fig. 4). The majority of these fish were females, and the sex ratio was 3 (females):1 (male) (Fig. 4). Although there is speculation that Nassau grouper are protogynous hermaphrodites (female to male, with the largest fish being males), the largest fish captured consisted of males and females (Figs. 4 & 6). The oldest fish was 78 cm TL, male, and 22 years old (Figs. 5 & 6). The majority of fish landed at the docks were 6-12 years old (Fig. 7). Figure 4. Length-frequency of Nassau grouper harvested from spawning aggregations off Long Island, Bahamas. Figure 5. Relationship between Nassau grouper total length (cm) and sagittal otolith age (years). Figure 6. Relationship between Nassau grouper total length (cm) and age (years) by sex. Figure 7. Age-frequency of Nassau grouper landed at Clarencetown, Long Island and collected from nearby spawning aggregations. PAPERS PRESENTED BASED ON 2003 WORK: Mr. Chris Taylor organized and hosted a special symposium on emerging technologies for surveying reef fish as part of the Annual Gulf & Caribbean Fisheries Institute meeting, British Virgin Islands, November 2003. Mr. Taylor is currently serving as editor for the proceedings from this special GCFI symposium, which will be published as the Gulf and Caribbean Institute Symposium: Emerging Technologies in Reef Fisheries Management-NOAA Professional Papers Series. Rand, P, C. Taylor, D. Eggleston. 2003. A stereo-video method for quantifying size distribution, density and three dimensional spatial structure of reef fish spawning aggregations. Annual Gulf & Caribbean Fisheries Institute meeting, British Virgin Islands, November 2003. Taylor, C., D. Eggleston, P. Rand. 2003. Nassau grouper (Epinephelus striatus) spawning aggregations: hydroacoustic surveys and geostatistical analysis. Annual Gulf & Caribbean Fisheries Institute meeting, British Virgin Islands, November 2003. Schull, J. & A-M. Eklund. Population characteristics of Nassau grouper from Bahamian spawning aggregations. Annual Gulf & Caribbean Fisheries Institute meeting, British Virgin Islands, November 2003. Taylor, C., D. Eggleston, P. Rand. 2003. Characterization of reef fish spawning aggregations using hydroacoustiocs, 3-D video, and visual surveys: complementary approaches and local extinction. NOAA/NMFS Beaufort Laboratory, Beaufort, NC, September 2003. MANUSCRIPTS AND PUBLICATIONS: Rand, P, C. Taylor, D. Eggleston. (in review). A stereo-video method for quantifying size distribution, density and three dimensional spatial structure of reef fish spawning aggregations. Gulf and Caribbean Institute Symposium: Emerging Technologies in Reef Fisheries Management-NOAA Professional Papers Series. Taylor, C., D. Eggleston, P. Rand. (in review). Nassau grouper (Epinephelus striatus) spawning aggregations: hydroacoustic surveys and geostatistical analysis. Gulf and Caribbean Institute Symposium: Emerging Technologies in Reef Fisheries Management-NOAA Professional Papers Series. Taylor, C., P. Rand, D. Eggleston, L. Whaylen, P. Bush (in review). Characterization of reef fish spawning aggregations using hydroacoustiocs, 3-D video, and visual surveys: complementary approaches. Marine Ecology Progress Series. Eggleston, D., C. Taylor, P. Rand, C. Dahlgren, A-M. Eklund, J. Schull (in prep.). Spawning aggregations f Nassau grouper in the Bahamas: apparent local extinction, habitat characteristics, and population structure. Conservation Biology. Schull, J., A-M. Eklund, A. Collins. Population characteristics of Nassau grouper from Bahamian spawning aggregations. U.S. Fish. Bull. APPLICATION OF KNOWLEDGE TO MANAGEMENT We have used 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 (contact Dr. Livingston Marshall, Office of the Primer Minister, Commonwealth of the Bahamas, LIVINGSTONMARSHALL@bahamas.gov.bs). The Nassau grouper fishery was closed during January 2004; however, this management action had little impact since Nassau grouper did NOT aggregate during January 2004. Our data suggest that a December closure would be much more effective at conserving Nassau grouper spawning aggregations, and we plan to promote this recommendation to the Bahamas Department of Fisheries. 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. ADDITIONAL PERSONNEL (Students, Other scientists, technicians, etc.): All personnel are listed according to a specific objective (see above). LOCATIONS & GPS COORDINATES OF RESEARCH SITES: All locations and GPS coordinates are provided in the results sections.

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