Diel movements and space use of Lutjanus analis at a spawning aggregation site: evaluating the efficacy of a seasonal closed area for management

Designing place-based management for species that reproduce in transient fish spawning aggregations (FSAs) requires knowledge of movements and space use around aggregation sites. We examined the efficacy of the Mutton Snapper Seasonal Closed Area (MSSCA) in St. Croix, United States Virgin Islands, in protecting Lutjanus analis from fishing during the spawning season. We used acoustic telemetry to identify the spatial and temporal patterns of movement of 24 mutton snappers over 3 spawning seasons. L. analis aggregated from March to July with peak abundance during April, May, and June. Unlike its congeners, which spawn at sunset, L. analis spawns in the early afternoon. We were able to determine that L. analis used the MSSCA as a staging area during nighttime hours but migrated daily outside the MSSCA for spawning. We also used data from an acoustic Doppler current profiler to examine the relationship between fish movements and coastal current patterns. Fish migrated west in the morning with the prevailing current, occupied the presumed spawning site at slack tide, and then migrated east, again with the prevailing current, back to the MSSCA. We noted that chronic poaching was highly prevalent during the spawning season, reducing the effectiveness of the MSSCA and market closure. In light of our findings, to improve management of the L. analis FSA, we recommend re-evaluating the MSSCA boundaries and timing, improving enforcement, and engaging fishers and the community through co-management efforts. Pro-active management is of particular importance, given that this may be the only L. analis FSA site on St. Croix.