Abstract
The demand for feed to the aquaculture industry has shown a strong increase over the last years in parallel with the increase in total production within the industry. Estimated growth in the fish farming industry is supposed to cause a permanent shortage of marine oils within a few years, and of marine proteins on a longer time scale. At present traditional marine biological recourses are exploited at the highest possible level. In many seas exploitation is far beyond any sustainable level. Thus, further increase in marine harvest to sustain growth in the aquaculture industry, cannot be based on the marine resources exploited at present. The only unexploited marine resources of significant biomass are found at lower trophic levels, comprised by populations of zooplankton and mesopelagic fish. A fishery on plankton should not be developed without quantitative knowledge about standing stock and production of marine plankton, and the effects of harvesting plankton on the ecosystem in general and on commercially harvested fish stocks in particular. The overall goal is to improve abundance estimates and assess stocks of zooplankton to enable quantification of ecological consequences of harvesting at lower trophic levels. Improved methods of abundance estimation and model driven stock assessment of plankton will form the basis of our approach. With knowledge of plankton population biomass and production at hand, effects of harvesting plankton can be explored by ecosystem models with respect to plankton populations themselves, the ecosystem and food requirement for commercial planktivorous fish stocks. The results will be disseminated as advice to managers. The contribution by HARVEST II to quantitative information about distribution, production and ecological role of plankton populations will also form an important knowledge base to the development of ecosystem-based management of fisheries.
Norway