Temporal and spatial trends in spawning aggregations of camouflage grouper, Epinephelus polyphekadion, in Pohnpei, Micronesia

Abstract

The aims of this investigation were to document the temporal and spatial dynamics of aggregated camouflage grouper, Epinephelus polyphekadion in Pohnpei, Micronesia, and to assess seasonal and daily patterns of spawning and reproductive behavior. Camouflage grouper aggregated and spawned adjacent to the Kehpara Marine Sanctuary (KMS), Pohnpei, Micronesia, during two consecutive months in 1998 and 1999. A combination of gonadosomatic indices, oocyte diameter analysis, and histological evidence confirmed that camouflage grouper spawned 1-2 days prior to full moon over an 8-9h period after dusk in each of the four study months. Males entered the site approximately 7 days prior to females and color variations were frequently observed. Significant differences were detected in mean size between the sexes. A series of management initiatives was initiated by the government in the 1980s to reduce fishing during aggregation periods, such as a March-April grouper sales ban, but these were largely ineffective. Following the 1998-1999 survey, several recommendations were made to halt aggregation fishing, including a commercial and subsistence catch and sales ban during spawning months, and the extension of the KMS to incorporate two additional grouper aggregations directly adjacent to it.