The trophic efficiencies of four fisheries were calculated on the basis of the size spectrum and productivity of both the phytoplankton and the fish. Results showed that for the Gulf of Alaska salmon fishery and the Strait of Georgia Pacific whiting fishery, the average ecological efficiency was 14.3% and 13.2%, respectively, for each step in the food chain. The Kaohsiung offshore fishery has the highest ecological efficiency of 16.2%. These results contrast with the Kaohsiung nearshore fishery, which has an average ecological efficiency of only 7.4%. This result could be explained in terms of eutrophication of the nearshore environment, which is known to lower trophic efficiency in aquatic habitats, or it could be due to overfishing in this area. The importance of calculating the trophic efficiency exponent lies both in being able to detect the overall effect of environmental or anthropogenic stress on a fishery, as well as in being able to use the exponent to calculate fishery production, from the size spectrum and productivity of the primary producers.
Primary productivity, Size spectra, Fisheries
