Terrestrial fatty acids as tracers of finfish aquaculture waste in the marine environment

Abstract

Waste from open‐cage aquaculture flows directly into the marine environment from uneaten feeds, faecal material and dissolved nutrients. Sustainable management outcomes are regularly based on the dispersal patterns of the waste, with biochemical tracing a key tool in understanding the footprint of aquaculture. We examined the use of fatty acid (FA) analysis to trace aquaculture waste for this purpose, with the aim of identifying specific biomarkers for environmental applications, as well as identifying challenges that are regularly encountered. Overall, the widespread use of terrestrial‐based oils in the production of marine aquaculture feeds has increased the use of FA biomarkers to trace aquaculture waste across benthic and pelagic systems, in vertebrates, invertebrates and environmental samples such as sediment and seston. A combination of linoleic acid (LA), oleic acid (OA) and α‐linolenic acid (ALA), which are dominant C18 FA in terrestrial seed and animal oils, is the most commonly used biomarkers, along with overall shifts in FA profile related to diet. A challenge regularly encountered, particularly in lower trophic species, was the capacity of an organism to biomodify or selectively spare certain dietary FA, which can mask assimilation of aquaculture‐derived FA. In these species, controlled feeding studies are needed to properly understand FA metabolism and to ensure correct interpretation of FA data collected from wild samples. Overall, as FA biomarkers have the capacity to link aquaculture waste in the environment with potential effect, they are a valuable and increasingly applied tool for examining the overall influence of aquaculture in marine ecosystems.

Limited evidence for differential reproductive fitness of wild Atlantic cod in areas of high and low salmon farming density

“…The outlying LFD fish was also high in linoleic acid (2.5%). Both oleic and linoleic acid can indicate consumption of commercial feed (Fernandez-Jover et al 2011b, White et al 2017c, and were marginally higher in the HFD group on average (6% and 18% increases, respectively), but this effect was not significant for either oleic acid (F 1,18 = 1.9, p = 0.2) or linoleic acid (F 1,18 = 0.4, p = 0.6). Levels of these fatty acids were strongly positively correlated with each other in the HFD group (Pearson's r = 0.90, t 8 = 6.0, p < 0.001), while this effect was non-significant in the LFD group (r = 0.44, t 8 = 1.4, p = 0.2).…”

“…We conducted several ovarian fatty acid analyses: initially, we made univariate comparisons of total lipids, cholesterol, and aquafeed markers oleic and linoleic acid across LFD and HFD groups using linear analysis of variance models. We then compared the entire suite of fatty acids across groups using a multivariate permutational analysis of variance (PERM-ANOVA) fitted to a Euclidean dissimilarity matrix using Primer 6 software (Anderson et al 2008, White et al 2017c.…”

“…Accordingly, our analysis of ovarian lipid composition may only have detected effects of a large dietary shift, while the presence of a single active salmon farm near 1 LFD location (affecting 25% of LFD fish) may have reduced overall differences in fatty acid profiles between HFD and LFD groups. Indirect intake of farm waste via predation of farm-associated invertebrates and fish, combined with dietary sparing and biosynthesis, may also weaken or mask fatty acid signals in fish that are not strongly farm associated (White et al 2017c). The strong correlation between levels of oleic and linoleic acids in the HFD group (less so in the LFD group) is consistent with (but not necessarily strong evidence for) a spectrum of farm association, with the most strongly farm-associated individuals in the HFD group having higher levels of oleic and linoleic acids than their counterparts in the LFD group.…”

Generation, characterization, perniciousness, removal and reutilization of solids in aquaculture water: a review from the whole process perspective

“…; White et al . ). However, formulated pelleted feed is the main food source of cultured fish currently, and feed residue is an important source of solids (Edwards ; Mo et al .…”

Effects of pollution on marine organisms

“…Crustacean and fish species along with one sea anemone (Anemonia sulcata) were the species with the lowest biomarker variation, while GST, SOD and HSP70 were the biomarkers with the lowest intraspecies variation, indicating they may be the best species and biomarkers to use in future studies. White, Woodcock, Bannister, and Nichols (2019) reviewed the use of fatty acids to determine the exposure of wild marine species to waste from fish farms. In field-collected fish there was a general trend toward increasing C 18 fatty acids (linoleic, oleic and α-linolenic acids) in fish feeding on aquaculture waste.…”