REPLACEMENT OF FEED FOR AFRICAN CATFISH (CLARIAS GARIEPINUS) WITH BYPRODUCTS FROM LOCAL FISHING: Are local fish wastes trash or treat, can they replace commercial feeds for more sustainable production?

Abstract

A persisting issue with current aquaculture practices is the large-scale demand for fishmeal in aquafeeds, which puts pressure on wild fish stocks as well as on markets, creating environmental and social dilemmas. Omnivorous warmwater species like African catfish hold the potential for local and sustainable fish production in recirculating aquaculture systems (RAS). But the feeds used in production facilities are largely fishmeal based, contributing to the global demand problematic. The use of locally available fish products has potential to be an alternative to traditional fishmeal. Two byproducts from the fishery industry in South Sweden are tested in this study. The first is trimmings like heads and carcasses from herring fisheries (H). The second is freshwater cyprinid fish, which are caught from lakes to reduce eutrophication (“reduktionsfiske“, R). I conducted a feeding trial in an experimental RAS, approximating commercial production conditions. For the three experimental groups C (control, standard catfish pellets), H, and R, I evenly distributed 90 African catfish into 12 tanks to create triplicates per group. After 30 days, the average weight increase per group was 55.6% in the control, 67.6% in the R, and significantly lower 25.6% in the H. The mean feed conversion ratio (FCR) per treatment group was 0.80 in C, 0,96 in H, and 0.63 in R. No difference in health and welfare was found between the treatment groups and the control group according to haematology and liver weight assessment. Altogether, the R feed showed very promising results because it showed good results in health and welfare, growth, FCR and final product taste. This locally and cheaply available feed or potential feed ingredient could be a starting point for more profitable production of sustainable African catfish feed in Sweden.