The goal of this project was to conduct research on the timing, connectivity and status of multi-species spawning aggregations of groupers currently under fishery management or conservation plans in the US Caribbean. The status of the fish spawning aggregations (FSA) is a key source of information to assess if the fishery is sustainable. Many species of grouper are part of the small-scale artisanal fisheries of the Caribbean, hence knowing the condition of their reproductive events is critical to provide information to managers and fishers. Groupers provided an important landing value in local fisheries, but some species have been protected from fisheries due to their population declines over the past 30 years. The main reason for these declines has been their historical capture during reproductive periods at FSAs where hundreds to thousands of individuals aggregate to spawn at predictable sites and times. Regulations to safeguard FSAs from the impacts of fishing became necessary because of the vulnerability of grouper during this critical life phase.
This project assessed multiple grouper FSAs simultaneously in Puerto Rico and the USVI that are currently under some type of protective measures. With the information generated by researchers the results provide information to evaluate these management strategies, namely: seasonal closures, seasonal areal closures, and permanent closures. However, this study is limited to grouper FSAs and not a population or stock assessment. Nonetheless the information on the presence and abundances of groupers as well as the variability of these numbers at FSAs provide timely information regarding these populations.
Specifically, the project studied FSA sites previously documented at Mona Island, Bajo de Sico in Puerto Rico and the Grammanik Bank in St. Thomas during 2016 and 2017. Species that are more common in the region and were assessed for this project include:
The abundance and size structure for groupers at the aggregation site was determined using a combination of diver-based underwater visual census techniques (surveys) with closed-circuit rebreathers (CCR) or SCUBA sometimes assisted with video cameras with laser calipers to accurately determine the total length of each Nassau grouper. The presence of spawning fish at the FSA was studied during two years and correlated with the sounds produced by each species that was simultaneously recorded with passive acoustic monitoring (PAM).
The sounds produced by each grouper species during their reproductive behaviors are recorded with an instrument called DSG and hydrophone during six months over 24 hrs. (20 seconds every 5 minutes). The recordings of the ambient sounds at FSA sites are analyzed manually and with latest technology speech recognition algorithms that can provide a detector that is species specific. This is a non-intrusive method that provides a high-resolution indication of reproductive activity with minimal effort. Examples of the sounds produced by grouper species.
At two sites Nassau grouper were also monitored with internal tags detected with an array of acoustic receivers to document the habitat use during the FSA. Local connectivity patterns were assessed by documenting patterns of movement of tagged grouper after the FSA when they migrate towards their home ranges. At least one Nassau grouper was detected near El Seco, Vieques after aggregating at the Grammanik Bank south of St. Thomas, a distance of at least 17 nautical miles (map).
As part of this project tissue from the fins of Nassau grouper was collected at both FSAs (Puerto Rico and USVI) to determine the genetic connectivity of the only two known spawning aggregations in the region with the latest molecular techniques, genome skimming. A complete Nassau grouper annotated genome (a genetic map) is currently being assembled based on one of these samples collected at the FSA in St. Thomas.
This project was conducted in collaboration with the Department of Marine Sciences of the University of Puerto Rico, the Caribbean Coral Reef Institute and the Center for Marine and Environmental Studies of the University of the Virgin Islands.
NOAA Award No: NA15NMF4270341 Project Title: Sustainability and recovery of groupers in Puerto Rico and the US Virgin Islands funded by the Saltonstall-Kennedy Grant Program and Office of Protected Resources, NOAA