Replacing dietary fish meal improves ecosystem services of largemouth bass (Micropterus salmoides) farming

Abstract

Sustainability of aquaculture industry depends on the value of ecosystem services (VES), which has been rarely quantified in aquaculture practices. The present study evaluated the impact of replacing dietary fish meal with soy protein concentrate (SPC) and cottonseed protein concentrate (CPC) on VES of largemouth bass Micropterus salmoides farming. A reference diet (RF) contained 400 g/kg fish meal, and 20%, 40% and 60% of the fish meal was replaced by either SPC (SPC20, SPC40, SPC60) or CPC (CPC20, CPC40, CPC60). Fish were fed with the test diets for eight weeks, and alternation in VES of three categories, including provision services, regulating services and cultural services, were calculated. No significant differences were found in weight gain, retention efficiencies of nitrogen and carbon, condition factor, proximate composition of whole body and nitrogen waste between fish fed diet RF and diets CPC20, CPC40, CPC60, SPC20, SPC40 and SPC60. Fish fed diet RF exhibited lower feed intake and feed conversion ratio, but lower carbon waste relative to fish fed diet CPC60, and higher phosphorus waste relative to fish fed diet SPC60. These results reveal that fish meal level in largemouth bass diet could be reduced to 160 g/kg by using SPC or CPC as a fish meal alternate, and replacing dietary fish meal did not result in apparent negative impact on regulating services of largemouth bass farming. The ratio of fish meal consumption to fish production declined with increasing fish meal replacement level, indicating provision services was improved by feeding diets CPC60 and SPC60. This study reveals, for the first time, that improvement of feeding management benefits to amplify VES of largemouth bass farming.