Habitat quality and fish population: impacts of nutrient enrichment on populations of European perch off the east coast of Sweden

Degradation of marine ecosystems through e.g., eutrophication and climate change is a concern for sustainable fishery management world-wide, but studies on associated impacts on fish populations are rare. This study examined the effects of eutrophying nutrient loads on perch populations along the Swedish east coast. A modified Gordon-Schaefer logistic growth model was used for econometric estimation of perch populations in the study area, based on annual time series data for the period 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 Copenhagen agreement, could increase the steady state perch population by 50%. Simple calculations showed that this could increase the discounted harvest value of the perch by 30%.