Protected Sex: Grouper Mating Calls in Marine Managed Areas
Published:13 Sep.2023    Source:Florida Atlantic University
A couple of months each year, groupers (Epinephelidae) gather in the hundreds and even thousands to mate under the full moon. This concentrated nature and short duration of mating, however, renders these species susceptible to incidental fishing and poaching. Although protective measures are in place through marine managed areas, these management zone boundaries may fail to fully encompass fish migration paths and chronological variability in fish spawning aggregations, especially for threatened species. Recent evidence suggests that some reproductive times are extending beyond months and locations for which the marine managed areas were established. Yet, impacts of protecting fish spawning aggregations with seasonal marine managed areas or market bans remain largely unknown.
A "call" of the wild inspired researchers from Florida Atlantic University's Harbor Branch Oceanographic Institute to follow and record grouper mating sounds at three marine managed areas off the west coast of Puerto Rico in the United States Caribbean. For the study, researchers used passive acoustics to locate spawning aggregations of two commercially important species -- the Nassau (Epinephelus striatus) and red hind (Epinephelus guttatus) groupers -- to determine temporal patterns in their reproductive behaviors as well as habitat use. These marine managed areas have focused on reproductive seasons through seasonal closures.

Results of the study, published in the journal Fisheries Research, reveal that known fish spawning aggregations sites are critical habitat for both Nassau and red hind species. Moreover, the existence of potential, previously unknown fish spawning aggregations for multiple grouper species also highlights the importance of spatial and temporal expansion of existing regulations. Researchers found a notable spread of courtship-associated sounds of approximately 500 meters of both spawning aggregation sites, which varied with the moon phase. The presence of multiple, smaller aggregations of red hind within fish spawning aggregations suggest increased spread such as to the southern shelf of the U.S. Virgin Islands. The variability in peak courtship-associated sound timing also suggests temporal variability is operating on sub-regional scales. Expanded or permanent closures of known fish spawning aggregations that include threatened species would accommodate for this variance in timing of aggregations, promoting their recovery.