Growth performance, fast muscle development and chemical composition of juvenile lumpfish (Cyclopterus lumpus) fed diets incorporating soy and pea protein concentrates

Florence Perera Willora,Nimalan Nadanasabesan,Helene Rønquist Knutsen,Cui Liu,Mette Sørensen,Ørjan Hagen

doi:10.1016/j.aqrep.2020.100352

Abstract

Lumpfish (Cyclopterus lumpus) are widely applied as biological delousers in open net-pen farming of Atlantic salmon. As a species new to farming it is necessary to obtain a comprehensive understanding of the capacity of lumpfish to utilize plant derived feed ingredients. A feeding trial lasting for 54 days was conducted to investigate the effects of replacing fishmeal (FM) with a mix of soy protein concentrate (SPC) and pea protein concentrate (PPC) on growth, body chemical composition, and fast muscle fiber cellularity in juvenile lumpfish. Four isonitrogenous and isoenergetic diets (52 % crude protein and 14 % crude lipid) were formulated; a FM based diet was used as control (CTRL), and three experimental diets containing SPC and PPC (equal proportions of 1:1), replacing FM on weight basis at 25 % (PP25) 50 % (PP50) and 75 % (PP75). The fish grew from approximately 6.9 g to an average weight of 40.2 g in 54 days. Fish fed PP50 had significantly higher body weight, length and height compared to the other dietary groups. The whole body crude protein content of fish fed PP50 was significantly higher compared to the CTRL diet, while crude lipids were lower than those on CTRL and PP25 diets. Ash and dry matter did not differ among groups. Probability density functions showed no differences in fast muscle fiber size distributions amongst feeding groups. A higher percentage of smaller fibers in all feeding groups indicated hyperplasia was the dominant mechanism of muscle growth during the experimental period. These results suggest that a mixture of SPC and PPC can replace up to 50 % of FM in diets for juvenile lumpfish without any adverse effects on growth, chemical composition and fast muscle fiber cellularity.

Highlights

Two species of caligid copepods, salmon louse (Lepoptherius salmonis, Krøyer) and sea louse (Caligus elongatus) are a significant threat to farmed and wild Atlantic salmon (Salmo salar)
The chemical analysis showed that crude protein was slightly lower and crude lipid was slightly higher than the calculated values, while ash and energy were similar to the calculated values
Length of the fish appeared to be proportional with weight gain and was significantly higher for fish fed PP50 compared to all other diet groups

Summary

Introduction

Two species of caligid copepods, salmon louse (Lepoptherius salmonis, Krøyer) and sea louse (Caligus elongatus) are a significant threat to farmed and wild Atlantic salmon (Salmo salar). Challenges associated with salmon lice have been reported since 1970 in Norway (Heuch et al, 2005), and have become the main issue for growth and expansion of Norwegian salmon production. Chemotherapeutants, such as bath treatments (hydrogen peroxide and organophosphates) or in-feed treatments (emamectin benzoate), have been used heavily to control these ectoparasites (Burridge et al, 2010). Interest in the commercial production of farmed lumpfish in Norway began in 2011 (Imsland et al, 2014a), as a alternative solution to the sea-lice infestation issue. Studies performed to date have confirmed that lumpfish can be efficient delousers, reducing the mature female lice levels by 93%–97% when cocultured with farmed salmon, at a stocking density of 10%–15%

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