Hawaii FEP - Western Pacific Fishery Council

parts of banks may be composed of rock, coral rubble, sand, or shell deposits. Banks thus supporta variety of habitats that in turn support a variety of fish species (Levington 1995).Fish distribution on banks is affected by substrate types and composition. Those suitable forlutjanids, serranids, and lethrinids tend to be patchy, leading to isolated groups of fish with littlelateral exchange or adult migration except when patches are close together. These types ofassemblages may be regarded as consisting of metapopulations that are associated with specificfeatures or habitats and are interconnected through larval dispersal.From a genetic perspective, individual patch assemblages may be considered as the samepopulation; however, not enough is known about exchange rates to distinguish discretepopulations.Seamounts are undersea mountains, mostly of volcanic origin, which rise steeply from the seabottom to below sea level (Rogers 1994). On seamounts and surrounding banks, speciescomposition is closely related to depth. Deep-slope fisheries typically occur in the 100–500meter depth range. A rapid decrease in species richness typically occurs between 200 and 400meters deep, and most fishes observed there are associated with hard substrates, holes, ledges, orcaves (Chave and Mundy 1994). Territoriality is considered to be less important for deep-waterspecies of serranids, and lutjanids tend to form loose aggregations. Adult deep-water species arebelieved to not normally migrate between isolated seamounts.Seamounts have complex effects on ocean circulation. One effect, known as the Taylor column,relates to eddies trapped over seamounts to form quasi-closed circulations. It is hypothesized thatthis helps retain pelagic larvae around seamounts and maintain the local fish population.Although evidence for retention of larvae over seamounts is sparse (Boehlert and Mundy 1993),endemism has been reported for a number of fish and invertebrate species at seamounts (Rogers1994). Wilson and Kaufman (1987) concluded that seamount species are dominated by those onnearby shelf areas, and that seamounts act as stepping stones for transoceanic dispersal. Snappersand groupers both produce pelagic eggs and larvae, which tend to be most abundant over deepreef slope waters, while larvae of Etelis snappers are generally found in oceanic waters. Itappears that populations of snappers and groupers on seamounts rely on inputs of larvae fromexternal sources.Within the Hawaii Archipelago, there are numerous banks and seamounts, with more observedin the NWHI rather than in the MHI. In the MHI, the largest bank is Penguin Bank which islocated southeast of Oahu.3.3.2.7 Deep Ocean FloorAt the end of reef slopes lies the dark and cold world of the deep ocean floor. Composed ofmostly mud and sand, the deep ocean floor is home to deposit feeders and suspension feeders, aswell as certain species of deep-sea fishes. Compared with shallower benthic areas (e.g., coralreefs), benthic seafloor areas are lower in productivity and biomass. Due to the lack of sunlight,primary productivity is low, and many organisms rely on deposition of organic matter that sinksto the bottom. The occurrence of secondary and tertiary consumers decreases the deeper one62