Feeding the river: The fate of feed-pellet-derived material escaping from land-based trout farms

Abstract : Environmental impacts of intensive fish cultivation on receiving food webs have been investigated mainly for cage culture systems in lake and marine ecosystems; however, the potential influence of land-based salmonid farms on rivers is less documented. Stable C and N isotopes were used to examine the influence of aquaculture waste on aquatic organisms in three streams with different discharge rates (1–5 m3·s−1) that receive effluents from rainbow trout (Oncorhynchus mykiss) farms with different rearing capacities (100–600 t wet weight per year). Feed pellets from each farm were significantly 13C-enriched (up to +8‰ δ13C) compared to the isotopic backgrounds of the receiving streams. Benthic invertebrates (detritivores and predators) and small-bodied fish were consistently 13C-enriched downstream the fish farm effluents. This pattern was stronger for low stream discharges and high-production farms. The trophic niche breadths of these organisms, estimated by the spread of their isotopic values. decreased in downstream these farms, suggesting a reduction in the diversity of dietary sources. Upstream-downstream comparisons based on multiple-source mixing models revealed high contributions (40–88%) of pellet-derived material in their diet, which indicates that waste from land-based salmonid farms enhanced the detritus-based food chain via this particulate route.
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Submitted on : Thursday, July 19, 2018 - 3:42:30 PM
Last modification on : Tuesday, June 4, 2019 - 5:03:46 PM

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J.M. Roussel, Alexis Guilpart, Dominique Huteau, Martine Perdriau, Marc Roucaute, et al.. Feeding the river: The fate of feed-pellet-derived material escaping from land-based trout farms. Aquaculture, Elsevier, 2018, 495, pp.172 - 178. ⟨10.1016/j.aquaculture.2018.05.050⟩. ⟨hal-01844669⟩

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