"Recovery and pulse recruitment of a Nassau Grouper spawning aggregation in the Cayman Islands"

Nassau Grouper (Epinephelus striatus) are ESA-listed due to dramatic declines in catch and the disappearance of roughly half of the known spawning aggregations in the Caribbean. The Cayman Islands protected the species in 2003 and the aggregation off Little Cayman is the largest currently documented. Here, we assess the Cayman Islands aggregations using non-invasive length data from diver-operated laser calipers. We document recovery from heavy fishing, a large recruitment pulse from 2011 spawning, and differences in growth between islands. Recognizing the importance of recruitment to population recovery, we investigate the dispersal of eggs and larvae from the aggregation using drogued drifters and a novel in situ plankton imaging system. We demonstrate the ability to distinguish development stages from spawning to hatching and observe 3D positions of individual eggs and larvae. We then fit a 3-dimensional diffusion-mortality model and use it to show that favorable ocean currents allowing self-recruitment is a possible mechanistic explanation for the strong 2011 year class of Nassau Grouper on Little Cayman.

Brian recently joined the NEFSC as an NRC postdoc with Tim Miller. Their goal is to generalize and extend Tim's state-space assessment framework to implement sub-models for incorporating environmental or climate effects on stock productivity or demographic attributes. They will also develop a user interface and apply the model to one or two stocks with
hypothesized environmental relationships. Brian completed his PhD at Scripps Institution of Oceanography with Brice Semmens. In addition to the Caymans Nassau Grouper work, he developed stable isotope mixing model software (https://github.com/brianstock/MixSIAR) and compared the ability of spatial models to predict bycatch using observer data.