CONTROL OF MARINE FISH PRODUCTION

In the trophic-dynamic hypothesis, biomass production was assumed limited by factors that control energy transfer. An analysis using trophic-dynamic models applied to ocean data, however, leads to a rejection of that hypothesis and supports a hypothesis that carnivorous fish production is controlled by the amount of new N annually incorporated into phytoplankton biomass and transferred through food webs. For an average 2.5 trophic transfers from phytoplankton to fish in environments ranging from oceanic to northeast North American coastal waters, N transfer efficiency was a constant 0.28 while C transfer efficiency increased nonlinearly from 0 to an asymptotic value of 0.16. Fish production was more sensitive to variations in phytoplankton production in oligotrophic than in eutrophic marine environments as a result of a nonlinear decrease in f, the ratio of new to total production, as primary production decreased.