Hawaii FEP - Western Pacific Fishery Council

MSYs for the Makapuu Established Bed have been estimated using a Beverton and Holt cohortproduction model (Beverton and Holt 1957) where data are available for Corallium secundum,and the Gulland Model (MSY = 0.4 MBo, where M=natural mortality and Bo is virgin biomass)for Gerardia and Lepidisis (Gulland 1970). The Gulland (1969) method to estimate MSY wasused for gold and bamboo corals at the Makapuu Bed, where information on populationdynamics is lacking. MSY is 40 percent of the natural mortality rate times virgin stock biomass(estimated from the product of area of the bed, average colony density and weighted averageweight of a virgin colony; MSY = 0.4 x M x B). The mortality rate for pink coral (M=0.066) isused as a proxy for other species.Table 17: MSY Estimates for Precious Corals in the Makapuu BedSpecies (common name) MSY (kg/yr) Method of calculationCorallium secundum (pink) 1,185 Beverton and HoltCohort production modelCorallium secundum (pink) 1,148 Gulland modelGerardia spp. (gold) 313 Gulland modelLepidisis olapa (bamboo ) 285 Gulland modelHarvest quotas for Hawaii’s four Conditional Beds have been extrapolated, based on bed size, bycomparison with that of the Makapuu Established Bed using the following formula forConditional Beds for which detailed data are unavailable (see Table 18).MSY for Makapuu Bed = MSY for Conditional BedArea of Makapuu BedArea of Conditional BedAs discussed in Section 4.4.5, the harvest quotas represent OY values and are based onextrapolations from “rounded down MSY values” for the Makapuu Bed.Commercial harvests of black coral have occurred in waters around Hawaii for more than threedecades. Significant harvests have been made from the Auau Channel and around Kauai. In1976, Grigg estimated black coral MSYs of 6,174 kg/yr for the Auau Channel and 1,480 kg/yearfor the area around Kauai using a Beverton and Holt yield production model (Grigg 1976). Morerecently, Grigg discovered a greater impact to the black coral resource from an invasive softcoral, Carijoa riisei, and based on that, coupled with harvesting impacts, estimated a reducedMSY of 3,750 kg/yr (Grigg 2004) for this area.No MSY estimates are available for the Exploratory Areas; however harvest quotas have beenimplemented based on available information (see Section 4.4.5).4.4.5 Precious Corals Optimum YieldAs discussed above, optimum yield (OY) values for the six Established and Conditional beds arebased on MSY estimates for the Makapuu Bed, which were rounded downward for ecologicalreasons. The rounded down MSY values were then extrapolated to the Conditional Beds basedon relative bed size. The OY for the Makapuu Bed is expressed as a two-year harvest quota118