Spatial and temporal characteristics of grouper spawning aggregations in marine protected areas in Palau, western Micronesia

In Palau, Ngerumekaol and Ebiil Channels are spawning aggregation sites that have been protected from fishing since 1976 and 2000, respectively. Groupers and other targeted fisheries species were monitored monthly over a 1.5 year period at these two spawning aggregations and two nearby exploited reference sites where grouper formerly aggregated to spawn. At the protected aggregation sites, three grouper species (Plectropomus areolatus, Epinephelus polyphekadion, and Epinephelus fuscoguttatus) accounted for 78% of the abundance and 85% of the biomass of all resource species surveyed but comprised <1% of the total abundance and biomass at reference sites not protected from fishing that formally harbored spawning aggregations. Abundance and biomass of grouper species pooled were 54% and 72% higher, respectively, at Ngerumekaol compared to Ebiil. Comparisons with data from the same locations in 1995–1996 showed order of magnitude declines in abundance of E. polyphekadion at both locations. The lower numbers of E. fuscoguttatus and the near absence of E. polyphekadion at Ebiil may reflect the effects of previous and current overexploitation.

► Groupers were monitored at two protected spawning aggregations sites. ► At these protected sites, groupers accounted for >75% of the total number and biomass. ► At unprotected sites, groupers comprised <1% of the total number and biomass. ► Comparisons with 1995–96 data show dramatic declines in populations at both locations. ► Grouper spawning aggregations differ in timing and duration at different locations.