Hawaii FEP - Western Pacific Fishery Council

The families of bottomfish and seamount fish that are often targeted by fishermen includesnappers (Lutjanidae), groupers (Serranidae), and jacks (Carangidae). Distinct depth associationsare reported for certain species of snappers and groupers. Many snappers and some groupers arerestricted to feeding in deep water (Parrish 1987). Species of the genus Pristipomoides occur atintermediate depths, often schooling around rocky outcrops and promontories (Ralston et al.1986), while Eteline snappers are deep-water species. Groupers (Serranidae) are relatively largerand mostly occur in shallow areas, although some occupy deep-slope habitats. Groupers ingeneral are more sedentary and territorial than snappers or emperors, and are more dependent onhard substrata. In general, groupers may be less dependent on hard-bottom substrates at depth(Parrish 1987). For each family, schooling behavior is reported more frequently for juvenilesthan for adults. Spawning aggregations may, however, occur even for the solitary species atcertain times of the year, especially among groupers.A commonly reported trend is that juveniles occur in shallow water and adults are foundin deeper water (Parrish 1989). Juveniles also tend to feed in different habitats thanadults, possibly reflecting a way to reduce predation pressures. Not much is known onthe location and characteristics of nursery grounds for juvenile deep-slope snappers andgroupers. In Hawaii, juvenile opakapaka (P. filamentosus) have been found on flat, featurelessshallow banks, as opposed to high-relief areas where the adults occur. Similarly, juveniles of thedeep-slope grouper, hāpu`upu`u (Epinephelus quernus), are found in shallow water (Moffitt1993). Ralston and Williams (1988), however, found that for deep-slope species, size is poorlycorrelated with depth.The distribution of adult bottomfish is correlated with suitable physical habitat. Because of thevolcanic nature of the islands within the region, most bottomfish habitat consists of steep-slopeareas on the margins of the islands and banks. The habitat of the major bottomfish species tend tooverlap to some degree, as indicated by the depth range where they are caught. Within theoverall depth range, however, individual species are more common at specific depth intervals.Depth alone does not assure satisfactory habitat. Both the quantity and quality of habitat at depthare important. Bottomfish are typically distributed in a non-random patchy pattern, reflectingbottom habitat and oceanographic conditions. Much of the habitat within the depths ofoccurrence of bottomfish is a mosaic of sandy low-relief areas and rocky high-relief areas. Animportant component of the habitat for many bottomfish species appears to be the association ofhigh-relief areas with water movement. In the Hawaiian Islands and at Johnston Atoll,bottomfish density is correlated with areas of high relief and current flow (Haight 1989; Haightet al. 1993a; Ralston et al. 1986).Although the water depths utilized by bottomfish may overlap somewhat, the available resourcesmay be partitioned by species-specific behavioral differences. In a study of the feeding habitatsof the commercial bottomfish in the Hawaii Archipelago, Haight et al. (1993b) found thatecological competition between bottomfish species appears to be minimized through speciesspecifichabitat utilization. Species may partition the resource through both the depth and time offeeding activity, as well as through different prey preferences.Precious Corals66