Sustainable Novel Feed Ingredients in Aquaculture During a Crucial Growth Period. An investigation of growth and behaviour of farmed Atlantic Salmon (Salmo salar)

Ever increasing pressure on global wild fisheries, coupled with a need for food security for a growing population have driven the expansion of the aquaculture sector. Commercial production widely uses feeds based on fish meal and fish oil, negating the full potential benefit of aquaculture for conservation of wild fish populations. Recent research effort has focused on the development of alternative feed ingredients that support commercial growth rates and fish nutritional needs, the most successful of which, soybean has even reached the commercial market. However, soybean based feeds are not without their ecological and physiological impacts.

This study aimed to assess two novel ingredients that are potential candidates to replace fish meal and soy bean meal and their effects on growth and survival of Atlantic Salmon fry. This research will also consider the potential impact of these novel proteins on behaviours such as swimming activity, boldness and exploration that can be related to fish welfare. The fry stage was selected as it is a crucial developmental period for Atlantic Salmon influencing both growth and behaviour to adulthood.

Two independent trials of 8 weeks were carried out. Trial 1 investigated the effect of Black Soldier Fly larvae (Hermetia illucens) meal at increasing increments of inclusion from 0% to 30%, replacing soy protein meal. Trial 2 investigated the effect of a Single Cell Protein (Paecilomyces variotii) meal at increasing increments of inclusion from 0% to 30%, replacing fish meal. In both trials a standard commercial diet was also tested for comparison.

This study found that both novel proteins tested are promising replacements for traditional aquafeed proteins. Specifically, Trial 1 found that Black Soldier Fly Larvae at low inclusion levels (7.5%) enhanced the performance of the soy protein diet, but at high inclusion levels was limiting to growth. No negative affects to welfare were detected for Black Soldier Fly larvae meal, however results suggest that diets high in soy protein may have negative implications for Atlantic Salmon in intensive aquaculture. Trial 2 found that the Single Celled Protein meal was a promising replacement for fish meal up to inclusion of 15% producing fish of comparable weight to the standard commercial diet. Additionally, no negative effects to welfare were indicated by this trial. This is the first study of this protein in Atlantic Salmon diets so there is need for further investigation to confirm these results.

Several key areas were highlighted for urgent future investigation. Firstly, there is a need to fully characterise the nutrient profiles of Black Soldier Fly larvae and Single Celled Proteins to enhance their application to sustainable Atlantic Salmon aquaculture and to optimise their use. Secondly, investigation of the long-term impact of these novel proteins on individual coping style through the full development cycle of Salmo salar will be necessary to facilitate the best performance and welfare in intensive aquaculture.