Environmental Efficiency Analysis of Cage Culture Fish Farming System; the Case of Mazandaran Province

The present study was conducted to assess the environmental efficiency of cage culture fish farming system and to make suggestions for reducing the pollutants emissions into the aquatic ecosystem in Mazandaran province. In the production cycle of 2017-18, there were 9 active fish cage farms which the pollutants loadings from each farm were calculated based on an indirect method. According to the results, per ton of produced fish, an average of 73.979 kg of nitrogen, 13.893 kg of phosphorus and 488.353 kg of carbon were released into the environment. Furthermore, feed conversion ratio (FCR = feed supplied/ body weight gained) varied between 0.897-4 with an average of 1.249 which indicates severe inefficiencies of feeding. Subsequently, the environmental efficiency scores of farms were evaluated based on an SBM-DEA model. The average environmental efficiency of farms was 0.599, indicating that there is a high potential for reducing pollutants emissions and improving environmental efficiency. Based on study findings, weak technical knowledge of farmers, especially in choosing the right time for start and the end of production cycles, and feeding mismanagements will lead to an increase in the amount of pollutants released into the aquatic environment. Thus, it is suggested that successful farms be encouraged by incentive policies to transfer their experiences to other farms in order to improve the environmental efficiency of cage culture system. This can be done through training courses using well trained instructors and successful farmers.