POTENTIAL OF CALANUS AS A FEED ATTRACTANT IN LOW FISH MEAL DIETS FOR ATLANTIC SALMON

Commercial salmon feeds that are mainly composed of plant ingredients, contain only 30% of fishmeal and fish oil (Ytrestøyl et al., 2015). Most likely, fishmeal and fish oil will be used in the future too, albeit at lower inclusion levels. The aquaculture industry is searching for substitute ingredients that provide extra benefits such as improved fish health and/or flesh quality. Although such ingredients, particularly those from marine resources are abundant in nature, they are largely untapped. One such resource is the marine zooplankton Calanus finmarchicus (calanus), that has the potential to be a high-value component in salmon feeds. Calanus is a copepod commonly found off the coast of Norway. This zooplankton is commercially harvested and used for extraction of high-value oil and proteins. The protein fraction has a balanced amino acid composition and contains low molecular water-soluble fractions that may have appetite-stimulating properties. The aim of the present research was to investigate the potential use of the marine copepod Calanus finmarchicus hydrolysate as a functional supplement in low-fishmeal and fishmeal-free diets for Atlantic salmon, Salmo salar.

The experiment was designed to employ a control diet (10% fishmeal, CO) and 2 Calanus hydrolysate-incorporated (at 1.5% in low-fishmeal (5%) diet, CL and at 3% in fishmeal-free diet, CH) diets. The feeding trial lasted for 7 weeks. The overall growth of fish from all groups was very good. Supplementation of Calanus hydrolysate in low fishmeal (5%) with high plant ingredients diets did not alter the feed intake, growth performance and health/welfare of the fish. The fish fed CH diet failed to achieve similar feed intake and growth performance as that of the CO-fed group. Taken together, it is possible to include Calanus hydrolysate at 1.5% in low-fishmeal (5%) diet without any negative effect, but the inclusion of 3% in the fishmeal-free diet for Atlantic salmon seems not adequate to compensate for the specific nutrients found in fishmeal.