No abstract

Understanding animal space use patterns is critical for ecological research and conservation efforts. An organism’s home range territory serves as the fundamental unit of space use and is the area repeatedly used for routine activities. Nassau grouper, Epinephelus striatus, once of high commercial fishery importance, are now on the IUCN’s Red List designated as Critically Endangered due to overexploitation. Known for the formation of large spawning aggregations, information on their movements and space use dynamics outside of the reproductive period are lacking. In this study, we used acoustic telemetry to quantify the non-spawning horizontal and vertical space use patterns of Nassau grouper at the Bajo de Sico seamount, a seasonally closed marine protected area (MPA) in Puerto Rico. Twenty-nine groupers were tagged with acoustic transmitters, of which, fourteen were tracked continuously over a three-year period. Tagged individuals displayed high site fidelity to home reef locations and individuals occupied home ranges of relatively small size that remained constant between years. There was a high degree of overlap of home range territories and in locations where multiple individuals occupied the same home reef, individuals maintained discrete vertical distributions. Nassau groupers were recorded making multiple forays to the spawning site outside of the reported spawning season, and two individuals underwent home reef site relocation. Results indicate relatively low contribution to ecological connectivity during the non-reproductive period, therefore high relative abundances of this species are needed to fulfill their ecological role at the community level. The results also highlight the importance of Bajo de Sico, an isolated seamount of relatively deeper depth, as critical habitat for primary home reef sites of Nassau grouper. These results provide a basis for adapting the current management strategy at this MPA to provide adequate protection to the non-spawning population of Nassau grouper.

No abstract

The Nassau grouper, Epinephelus striatus, is a slow‐growing, late‐maturing, long‐lived reef fish widely distributed throughout the south‐western North Atlantic. Known for forming large spawning aggregations, numbering tens of thousands, they are now listed as Critically Endangered by the International Union for Conservation of Nature (IUCN). Recently, the only Nassau grouper spawning aggregation in Puerto Rico was documented at Bajo de Sico, a seamount and seasonally closed marine protected area. Studies elsewhere on the spatio‐temporal dynamics of Nassau grouper aggregations have documented how, and how far, fish move from home sites to the spawning site, and have shown the tight link between aggregation formation and the lunar cycle. However, these studies have not evaluated the potential impacts of the reduced spatial extent represented by a seamount, nor have they addressed the impacts of local seasonal protection relative to the size of the closed area and the timing of aggregation formation. Acoustic telemetry was used to quantify the spatio‐temporal dynamics of Nassau grouper spawning aggregation formation at Bajo de Sico. Twenty‐six individuals were tagged and tracked over three consecutive spawning seasons. Nassau grouper formed three or four aggregations per season, corresponding to the lunar cycles from January to April. Individuals displayed high visitation rates to the aggregation site: 98% visited at least two peaks per season; 80% visited multiple seasons. The timing of arrival, departure, and residency at the site were significantly different among individuals and lunar months, indicating significant variability in aggregation formation. Nassau grouper occupied a relatively small staging area (2.7 km2) and courtship arena (0.67 km2) compared with aggregations occurring on continental/insular platforms or large atolls; movements off the seamount may occur but were not detected. Results indicate the current seasonal closure inadequately protects the spawning population on Bajo de Sico and should be extended to the end of June.