Environmental Biology of Fishes 63: 27–39, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands. Temporal and spatial trends in spawning aggregations of camouflage grouper, Epinephelus polyphekadion, in Pohnpei, Micronesia Kevin L. Rhodes & Yvonne Sadovy Department of Ecology and Biodiversity, The University of Hong Kong, Pokfulam Road, Hong Kong, China (e-mail: yjsadovy@hkusua.hku.hk) Received 27 April 2000 Accepted 22 May 2001 Key words: reproduction, Serranidae, coloration, behavior, management Synopsis 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 8–9 h period after dusk in each of the four study months. Males entered the site approxi- mately 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 ineffec- tive. 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. Introduction Many large reef fish species aggregate briefly, and in large numbers, to spawn at specific times and loca- tions each year (Smith 1972, Thresher 1984, Shapiro 1987, Colin 1992, Domeier & Colin 1997). In some cases, hundreds to tens of thousands of individuals are known to travel long distances from home reefs to assemble for brief periods (one to several months each year) to reproduce (Burnett-Herkes 1975, Colin 1992, Carter et al. 1994, Sadovy 1996, Luckhurst 1998). Best known examples include many species of grouper (Serranidae), snapper (Lutjanidae), jack (Carangidae) and surgeonfish (Acanthuridae) (Domeier & Colin 1997). For many of these species it is likely that the spawning aggregations represent all reproductive activity for a given year (Shapiro et al. 1993a). There is limited evidence to suggest that for some species, individuals consistently return to the same aggregations from year to year (Luckhurst 1998, Johannes et al. 1999). For such individuals, and for the populations or subpopulations that form specific aggregations, long- term aggregation persistence may be critically impor- tant for population maintenance and genetic diversity (Bohnsack 1 , Smith et al. 1991). Fishers often target spawning aggregations since they are consistent in time and space. When fish- ing pressure is low, and a relatively small propor- tion of spawners is removed, aggregations persist (Sadovy 1994). When fishing pressure removes a high proportion of aggregating fish each year, however, aggregations may quickly decline and, within a few 1 Bohnsack, J.A. 1989. Protection of grouper spawning aggre- gations. National Marine Fisheries Service, Southeast Fisheries Coastal Resources Division Report No. CRD-88/89-06. 8 pp.