On the Environmental Impact of Freshwater Fish Farms in Greece and in Iceland

Abstract

In the present study, we focused on the nitrogen and phosphorus levels generated by open flow freshwater fish farms in Greece and Iceland where salmonid fish are cultivated. There are several differences in the legislation and regulation of the aquaculture sector in Greece and in Iceland. Nevertheless, in both countries, environmental protection agencies need accurate information for nutrient processes in order to evaluate the environmental influence on surrounding waters by salmon aquaculture. Data were collected from surveys of 21 freshwater fish farms in Greece and 9 in Iceland. The surveyed farms practiced intensive production methods. The concentrations of nitrogen and phosphorus in farms’ discharges were used to estimate organic load generated. The collected data were compared with data from the literature for the production Salmonids for species cultivated in Iceland (Arctic charr, Atlantic salmon) and in Greece (Rainbow trout). The results of the analysis indicate that in both countries the highest concentrations of nitrogen and phosphorus discharges of fish farms exhibits a variability which can be attributed to the total biomass of produced fish, fish feed and feeding management protocols used, species cultivated and ambient temperature. During the last 30 years, there was a significant reduction in the amount of nutrients generated by fish farms, which to a great extent is a result of lower levels of protein content in fish feeds and improved feed conversion efficiency. It is estimated that over the past 30 years, the combined effect of reduced nitrogen and phosphorus content and the improvements in Feed Conversion Efficiency, resulted in about 50% reduction in the nutrients generated by every Kg of farmed fish produced. Nevertheless, this significant improvement was easily offset by and increased production of fresh water fish farms exhibited in both countries. It seems possible that legislative measures combined with improvements in technology and feed management of fish farms will continue to be good option of minimizing the environmental impact of fish farms in the future.