Hawaii FEP - Western Pacific Fishery Council

jacks), whereas those in the MHI are not (Friedlander and DeMartini 2002). Some fish speciesthat are common in parts of the NWHI are rare in the MHI (Green 1997).Coral Reef ProductivityCoral reefs are among the most biologically productive environments in the world. The globalpotential for coral reef fisheries has been estimated at nine million metric tons per year, which isimpressive given the small area of reefs compared with the extent of other marine ecosystems,which collectively produce between 70 and 100 million metric tons per year (Munro 1984; Smith1978). An apparent paradox of coral reefs, however, is their location in the low-nutrient areas ofthe tropical oceans. Coral reefs themselves are characterized by the highest gross primaryproduction in the sea, with sand, rubble fields, reef flats, and margins adding to primaryproduction rates. The main primary producers on coral reefs are the benthic microalgae,macroalgae, symbiotic microalgae of corals, and other symbiont-bearing invertebrates(Levington 1995). Zooxanthellae living in the tissues of hard corals make a substantialcontribution to primary productivity in zones rich in corals due to their density—greater than 10 6cells cm -2 of live coral surface—and the high rugosity of the surfaces on which they live, as wellas their own photosynthetic potential. However, zones of high coral cover make up only a smallpart of entire coral reef ecosystems, so their contribution to total coral reef primary productivityis small (WPRFMC 2001).Although the ocean’s surface waters in the tropics generally have low productivity, these watersare continually moving. Coral reefs, therefore, have access to open-water productivity and thus,particularly in inshore waters, shallow benthic habitats such as reefs are not always the dominantsources of nutrients for fisheries. In coastal waters, detrital matter from land, plankton, andfringing marine plant communities are particularly abundant. There may be passive advection ofparticulate and dissolved detrital carbon onto reefs, as well as active transport onto reefs viafishes that shelter on reefs but that feed in adjacent habitats. There is, therefore, greater potentialfor nourishment of inshore reefs than offshore reefs by external sources, and this inshorenourishment is enhanced by large land masses (Birkeland 1997a).For most of the Pacific Islands, rainfall typically ranges from 2.0 to 3.5 m per year. Low islands,such as atolls, tend to have less rainfall and may suffer prolonged droughts. Furthermore, whenrain does fall on coral islands that have no major catchment area, there is little nutrient input intosurrounding coastal waters and lagoons. Lagoons and embayments around high islands in theSouth Pacific are, therefore, likely to be more productive than atoll lagoons. There are, however,some exceptions such as Palmyra Atoll and Rose Atoll which receive up to 4.3 m of rain peryear. The productivity of high-island coastal waters, particularly where there are lagoons andsheltered waters, is possibly reflected in the greater abundance of small pelagic fishes such asanchovies, sprats, sardines, scads, mackerels, and fusiliers. In addition, the range of differentenvironments that can be found in the immediate vicinity of the coasts of high islands alsocontributes to the greater range of biodiversity found in such locations.Coral Reef Communities59