Wondmagegn Tafesse Tirkaso

Degradation of marine ecosystems through, e.g., eutrophication and climate change is a concern for sustainable fishery management worldwide, but studies on associated impacts on fish populations are rare. This study examines the effects of eutrophying nutrient loads on the economic value of perch populations along the Swedish east coast by estimating the effects of nutrient loads on the population of perch and, then, simulates the harvest value of future perch population under the changes in nutrient loads. A modified Gordon-Schaefer logistic growth model was used for econometric estimation of perch populations based on annual time series data for the period of 1970-2014. Regression analysis using the fully modified ordinary least square (FMOLS) estimator revealed that phosphorus loads had significant effects on the perch population. A 40% decrease in phosphorus loads, as suggested by the international HELCOM agreement, could increase the steady state perch population by 50%. Simple calculations showed that this could increase the total discounted recreational and commercial harvest value of the perch by 30% over a 30 year period.