An approach to the one stock-multiple fisheries problem on the red sea bream management in the Chikuzenkai.

A simple method was developed for analysing the regulation effects in multiple fisheries exploiting one stock competitively, with special reference to the red sea bream stock in the Chikuzenkai. This method is applicable when fisheries are stable from year to year in spite of recruitment fluctuation and when natural mortality rates, individual growth and prices of catches are yearly unchanged.Two types of fishery production (yield per recruit and fishing revenue per recruit by fishery) were evaluated from an arbitrary cohort, whose values are the same among different cohorts. The sensitivities of such relative production against a reduction in the fishing intensity of a specific fishery were calculated.Regulation of a particular fishery for the young red sea bream of 0 and 1 year old will benefit other fisheries. Such regulation at specific ages in months will even increase production of the regulated fishery itself.