Growth, health and biochemical composition of the sea cucumber Cucumaria frondosa after multi-year holding in effluent waters of land-based salmon culture

A Mercier,BL Gianasi,M Graham,JF Hamel,J Sun

doi:10.3354/aei00356

Abstract

Methods have been proposed to mitigate the environmental footprint of aquaculture, including co-culture of species occupying different trophic levels. In this study, sea cucumbers Cucumaria frondosa, either from production tanks fed with effluent water from land-based salmon culture over 4 yr or collected from the field, were compared using stable isotope, lipid and fatty acid (FA) signatures as indicators of waste assimilation, health and biochemical composition. Enrichment of δ13C in muscle bands and intestine and of δ15N in muscle bands, gonad and intestine was detected in captive individuals relative to wild individuals, suggesting the uptake and assimilation of waste from salmon culture. The higher levels of FA biomarkers typical of salmon feed (18:1ω9, 18:2ω6 and 20:1ω9) and lower ω3/ω6 ratio in the captive sea cucumbers were also in line with assimilation of the waste. However, male and female sea cucumbers from the co-culture became smaller with time, their organ indices were lower than those of wild individuals (e.g. poorly developed gonad), and their biochemical composition differed: triacylglycerol content was greater in wild individuals and phospholipid content was greater in captive individuals. Also, FA profiles of all tissues differed between the 2 groups, whereas total lipid in muscle bands and gonad remained similar. Overall, results support that co-culture with suspension-feeding sea cucumbers may help mitigate the salmon industry footprint. In turn, the biochemical composition of the sea cucumbers changed, and their reduced size and body indices suggest that this food source does not provide suitable nutrients to sustain growth and reproduction.

Highlights

Atlantic salmon Salmo salar is one of the most intensively farmed marine fish, owing to its amenability to high stocking densities and rapid growth, and to well established international markets (Jobling et al 2010)
Sea cucumbers held in the integrated multi-trophic aquaculture (IMTA) system displayed enrichment in δ13C and δ15N relative to those collected from the wild (Fig. 3)
While Cucumaria frondosa has been identified as a potential candidate for IMTA, limited information currently exists on the suitability of this species or any suspension-feeding sea cucumber in such systems

Summary

Introduction

Atlantic salmon Salmo salar is one of the most intensively farmed marine fish, owing to its amenability to high stocking densities and rapid growth, and to well established international markets (Jobling et al 2010). To make fish farming more sustainable in the long term, emphasis has been placed on exploring landbased models (Shpigel et al 1993) and/or using integrated multi-trophic aquaculture (IMTA), which has the potential to reduce waste loading and environmental impacts and to increase the efficiency and productivity of intensive monoculture systems (Neori et al 2004). IMTA makes use of by-products, including wastes, from one aquatic species to provide nutrients to another (Troell et al 2009, Chopin et al 2012). IMTA involves the culture of aquatic animals and the use of their waste products (excess feed and feces) as a food source for other commercially viable extractive species to favor environmental remediation, economic stability and social acceptability (Ridler et al 2007, Troell et al 2009). Many species have successfully been integrated into IMTA systems to extract inorganic and organic waste, such as seaweed (Kang et al 2008, Abreu et al 2011), mussels (Reid et al 2010, MacDonald et al 2011, Irisarri et al 2015) and sea urchins (Orr et al 2014, Sterling et al 2016)

Methods

Results

Conclusion