Nonetheless, our findings from Grand Cayman, while sparse, highlight the challenges of motiving FSA recovery in areas near large human populations. Because the total annual reproductive output for a stock happens over a short window of time and a single location, it is reasonable to expect high variability in recruitment (25, 26). Nassau grouper may also provide important ecological service as a control on populations of mesopredators (59, 60) and as a potential predator of the invasive lionfish (61, 62). Across all years and both islands, we tagged 934 fish (Table 1). Recovery of critically endangered Nassau grouper (. None of the final models have parameters with Gelman–Rubin statistics larger than 1.05, suggesting each achieved convergence. Derniers chiffres du Coronavirus issus du CSSE 02/12/2020 (mercredi 2 décembre 2020). Records from Cuba suggest that annual Nassau grouper catch, at its maximum in the 1960s, reached 1,800 t, although subsequent decades showed steady declines until collapse by the 1990s (30). Image credit: Aurora Fernández Durán (photographer). 1B), during the winter spawning periods from 2005 through 2018. However, because individual sample sizes (the number of fish sides counted in survey i) were small relative to the total population size, N, the hypergeometric distribution is approximated by the binomial distribution (51). It is not clear if this lack of evidence stems from management ineffectiveness (e.g., enforcement/compliance failures), population processes, e.g., Allee effects (3, 42, 43), recruitment variability (44, 45), or an absence of data sufficient to document success. Importantly, the government also partnered with academic and nonprofit organizations to establish a research and monitoring program (Grouper Moon) aimed at documenting the impacts of conservation action. Across these studies, seasonal and place-based protections emerge as common management actions for success. Click Advance year 10 times. Such overfishing is often masked by hyperstability, whereby catch-per-unit effort (CPUE) at the FSA remains high despite steep population declines (12⇓⇓⇓–16); as a result, the onset and persistence of fisheries-induced population decline is poorly detected. The Nassau grouper (Epinephelus striatus), once the most important reef fishery in the Caribbean, exemplifies the risks associated with FSA fishing (17). Due to the timing and site fidelity of the spawning aggregations and the ease with which these relative loners can be caught while congregat… Shedd’s research vessel, the R/V Coral Reef II, is indispensable to our conservation research and education programs. The proportion of tagged sides of fish in the FSA is equal to:py=Ky/(2Ny),[3]. L.W. 2). Regardless of the modeling methods or data sources used, the size of Nassau grouper FSAs on Little Cayman and Cayman Brac have increased. Pull on a pair of tall rubber boots and experience what it’s like to be a marine mammal trainer! As a result of its decline, the Nassau grouper is now listed as Endangered on the IUCN Red List. Here, we develop an integrated population model of 2 Cayman Nassau grouper stocks based on both diver-collected mark-resight observations and video censuses. The Little Cayman model including video census data ran from 2005 to 2018 (the range of years during which we captured video census, except 2007, 2011, and 2016, when conditions and fish behavior precluded video capture). To date, few published studies have quantitatively demonstrated the efficacy of such management strategies even after several decades of aggressive management (e.g., complete fishing moratoria). Fish spawning aggregations: Where well-placed management actions can yield big benefits for fisheries and conservation, “Landings, effort and socio-economics of a small-scale commercial fishery in The Bahamas”, Tourism-related drivers of support for protection of fisheries resources on Andros Island, The Bahamas, The impact of nassau grouper size and abundance on scuba diver site selection and MPA economics, Fishing down a Caribbean food web relaxes trophic cascades, Indirect effects of an exploited predator on recruitment of coral-reef fishes, Grouper as a natural biocontrol of invasive lionfish, Predation on the invasive red lionfish, Pterois volitans (Pisces: Scorpaenidae), by native groupers in the Bahamas. Once FSAs are discovered, they are fished intensively; many such aggregations have ultimately been fished to the point where fish cease to aggregate (31⇓⇓–34). The videos were typically enumerated by advancing the video slowly while continuously counting fish, advancing across paused frames and counting fish in still images, or some combination of these methods. analyzed data; and L.W., S.A.H., and B.X.S. These issues, in part, led to the development and passage of the legislation establishing complete seasonal closures on the fishery in 2016. © Shedd Aquarium 2020. To date, however, clear evidence remains scarce that such management actions can succeed. They proposed to list the species as endangered. Author contributions: S.A.H., C.V.P.-S., C.M., P.B., B.C.J., and B.X.S. For Cayman Brac, the model results show minor increases in population size between 2008 and 2017 and then a large increase in the population size in 2018 to ∼1,900 fish (95% Bayesian CI, 1,346 and 2,820; Fig. In B, boxplots display counts from video censuses (jittered slightly along the x axis for ease of viewing). 2). By all indications, despite existing protections in the Bahamas, Nassau grouper populations are declining. The Nassau grouper can be identified by three distinct features: 1) its body is covered in five olive-brown vertical bars, and a diagonal bar goes from its snout, across its eye and to the start of its dorsal fin; 2) the top of its head has a tuning-fork shaped marking; and 3) the base of its tail has a large black saddle spot. We modeled the true number of fish at the aggregation site each year, Ny, in log space using a state–space model, with the following state process:log(Ny+1)=log(Ny)+μy,[1]. Second, multiple studies of aggregating grouper species have demonstrated high FSA site fidelity across spawning seasons, suggesting FSA attendants represent a persistent catchment of regional stocks (69⇓⇓–72). Eq. Copyright © 2020 National Academy of Sciences. 2 and 3), may provide a clue as to the cause of this delay. IL Overfishing of tropical grouper- and snapper-spawning aggregations is a globally pervasive problem, but evidence is elusive that recovery can occur following stock collapse. Heavy fishing has led to the collapse of many spawning aggregations, including a spawning aggregation at one of Shedd’s study sites, because so many fish were removed. 1. Normally solitary and territorial, during the winter full moons grouper travel, sometimes over great distances, and “group” together to spawn. The spatiotemporal predictability of Nassau grouper FSAs makes them particularly susceptible to overfishing during the spawning season (2). The close-up map shows the historical site on the east end of Little Cayman (circle) and active spawning sites on the west end of Little Cayman and the east end of Cayman Brac (triangles). Furthermore, despite having the same level of protection, the population on Cayman Brac appears to have only very recently undergone population expansion. Using these counts, we generate estimates of the number of spawning adults and, importantly, provide confidence intervals associated with these counts. Mapping each grouper's movements. Since the discovery of the west-end Little Cayman FSA, Reef Environmental Education Foundation (REEF) and the CI-DoE have monitored Nassau grouper FSAs in the Cayman Islands through the collaborative Grouper Moon Project. In Little Cayman, for instance, after 15 y of protections, the population has only very recently recovered to near the estimated size of the FSA when discovered in 2001. Shedd’s research will inform management decisions for Nassau groupers in the Bahamas and help ensure strategies are based on sound science. All groupers were reported together for fishery landings data, and specific data on Nassau grouper catch is limited. Historically, some Nassau grouper FSAs may have hosted upwards of 100,000 individuals (27), attracting fish from as much as 260 km away (28, 29). Centre commercial et culturel du pays, elle en est la plus grande ville avec 274 400 habitants (recensement de 2016), dont l'étendue est telle, qu'elle occupe la quasi-totalité de l'île de New Providence et se confond avec elle. The U.S. National Marine Fisheries Service recently completed a review of the status of the species for Endangered Species listing. We chose these tagging targets to balance the potential negative impacts of tagging with the need for consistent mark–resightings. We use the following priors in the model: a uniform distribution with bounds −10 and 10 for μ¯; a uniform distribution with bounds 0 and 10 on σproc; and for Ny=1, an island-specific uniform distribution (0,1000 for Cayman Brac and 0,5000 for Little Cayman). Our group saw small gatherings of fish, 4-8 at the most. 1A) have a long history of Nassau grouper exploitation and a more recent history of overexploitation (see SI Appendix, Supplement A, Table S1 for a Cayman Island Nassau grouper fishery history). However, the genetic structure, diversity and connectivity of Nassau grouper populations remain poorly understood and unexplored for most of The Bahamas. 3). By separating the process and observation components of our model framework, we afford the flexibility to inform the process model by more than one class of observations, e.g., an integrated population model (49). Now they can follow where individual groupers move throughout the year, including during the long spawning migrations. Regardless of the specific mechanisms leading to the apparent delayed recovery, it is clear that persistent long-term protections have the potential to ultimately foster recovery. The tag color was changed year-to-year as some tags remained on individuals for up to 3 y. and B.X.S. Map showing location of the Cayman Islands in the greater Caribbean region (A) and close-up of the islands of Little Cayman and Cayman Brac (B). Subsequently, in 2016, the Cayman Islands government enacted legislation aimed at recovering Nassau grouper (46). Membership benefits include free daily admission to the aquarium and other exclusive perks. The model with surveyor effect was ∼140 DIC units lower than the basic model, suggesting strong support for differences in tag-detection ability among surveyors (Table 2). The integrated population model applied to data from Little Cayman suggests that the abundance of Nassau grouper at the FSA may have declined somewhat between 2005 and 2008, despite spawning-site protections beginning in 2003. Changing environmental conditions and genetic adaptations may explain how penguins radiated and expanded their geographic ranges to encompass diverse environments. This spawning behavior makes the species vulnerable to overfishing. A dramatic year-over-year increase in Little Cayman FSA abundance (e.g., 2016 to 2017) may be due to episodic recruitment, given that 1) the species has a pelagic larval duration of between 35 to 45 d (21, 22), so stochastic oceanography may play a substantial role in establishing a successful year class, and 2) the proximal populations of Nassau grouper in the region have been fished to collapse (23, 24, 79), so consistent larval supply from elsewhere is nonexistent. In B, boxplots (see Fig. Diving biologists moor acoustic telemetry transmitters to the ocean floor. Typically, this data type would be modeled using the hypergeometric distribution, a special case of the binomial distribution applicable when sampling is without replacement. We analyze a uniquely rich research and monitoring dataset from spawning aggregations in the Cayman Islands to reconstruct annual Nassau grouper spawner abundance across almost 2 decades of postcollapse adaptive-fisheries management. Due to the limited amount of data from Cayman Brac for the tagging model, we did not attempt to fit the Cayman Brac model with random surveyor effects. They are using acoustic telemetry, a technology that uses sound pulses—pings—to track individual fish’s movements. The apparent failure of the Grand Cayman FSA to respond to management action may reflect the Allee effects described above. We treated yearly population growth, μy, terms as random effects drawn from a normal distribution with a mean μ¯ (the model-estimated overall population mean growth rate in log space), and SD σproc (process error). To evaluate the assumption that the mean proportion of tagged fish remains constant across all surveys collected, we subset the data and compared model results from 1) all survey data, 2) surveys from dives on which more than 10 surveys were completed (i.e., dives where survey conditions were good), and 3) surveys from the day prior to, on, and after peak spawning (i.e., surveys conducted around the night we observed the most spawning). where, Vm,y is the count made by reviewer m of video from year y; Ny is the spawning population in year y; and σy is the SD in year y. R2jags: Using R to run ‘JAGS,’ version 0.5-7 (2015). In both A and B, the black dots show the median posterior estimates, and the shaded boxes show the 95% Bayesian CI in years with observations (tag and/or video census counts). The 2 estimates of FSA size on the east-end Grand Cayman site yielded similar estimates of abundance (500 or less fish) despite a 6-y interval between the observations. Because of the implementation of these deliberate, science-based conservation strategies, Little Cayman is now home to the largest remaining identified Nassau grouper aggregation anywhere in the world. Copyright © 2020 the Author(s). Au niveau mondial le nombre total de cas est de 64 007 836, le nombre de guérisons est de 41 170 820, le nombre de décès est de 1 483 401. These findings demonstrate that spatial and seasonal closures aimed at rebuilding aggregation-based fisheries can foster conservation success. Nearly all studies presenting evidence for FSA overfishing rely on estimates of spawner abundance or catch at FSAs as a proxy for population status. The weather is beautiful, and the water is calm: perfect conditions for studying sharks. Temporarily closed but virtual programs are still open! We found that posterior estimates of annual population size differed minimally (SI Appendix, Supplement C, Fig. Since 2014, Shedd researchers have been studying Nassau grouper spawning aggregations in the Bahamas. The only other study we are aware of that documents recovery of a Nassau grouper population comes from the US Virgin Islands Grammanik bank, were divers estimated a change in FSA size from ∼30 to ∼100 fish over a 5-y window of time (based on diver observations such as those we present here for Grand Cayman). Surveyors typically achieved 5 to 20 surveys per dive (Table 1). Historically, some Nassau grouper FSAs may have hosted upwards of 100,000 individuals (27), attracting fish from as much as 260 km away (28, 29). However, the surprisingly high interannual variability in estimates of FSA size on Little Cayman, particularly when considering the mark–resight only model results (Figs. We compared the relative performance of different model parameterizations (parsimony) by calculating the difference between the DIC of each model and that of the model with the lowest DIC (∆DIC). That, and because hyperstability tempers the value of such data for assessments, we developed and implemented a long-term (15+ year) diving-based census program to estimate fish abundance at FSAs in the Cayman Islands. Because surveyors made every effort to avoid sampling the same fish within a count of 50, sampling was effectively conducted without replacement. At predictable times and locations each year, individuals gather to reproduce. While prior to fishery collapse, the CI-DoE collected CPUE data from aggregation-based fisheries (8), FSA closures precluded the continuation of these data. performed research; L.W. For the purposes of this study, we assumed that the abundance of spawners at the FSAs on each island provide a direct proxy for the total spawning stock of Nassau grouper on that island. A survey consists of the count of tags (resights) seen from 50 fish. See online for related content such as Commentaries. To evaluate convergence, we calculated the Gelman–Rubin statistic for every parameter, along with the number of parameters with Gelman–Rubin statistics greater than 1.01, 1.05, and 1.10. The targeting of reef fish FSAs has resulted in pervasive overfishing of aggregating species throughout the world’s oceans (14). Nassau, anciennement Charles Town, est la capitale des Bahamas. The first one is the Nassau grouper species while the second one is the Black grouper species. To collect a video census, a diver started recording video at one end of the band and traversed the length of the band while keeping aggregating fish within the camera frame. Larvae do not necessarily recruit to the locations in which they were spawned; population genetic studies show broad (but not complete) connectivity across the Caribbean (23, 24). Following concerns of decreased catch voiced by Caymanian fishermen in the 1980s, the Cayman Islands Department of Environment (CI-DoE) began collecting catch data during the spawning season and carried out age and growth studies for the species in 1987 (8). designed research; L.W., S.A.H., C.V.P.-S., C.M., P.B., B.C.J., and B.X.S. NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. Species vulnerable to overfishing during the spawning population captured in the tropical western Atlantic for up to y! Up populations of a number of fish, 4-8 at the same level of protection, the of! Window of time ( Fig adaptive management will lead to nassau grouper population recovery Grand. 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2020 nassau grouper population