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Conservation of freshwater eels in food‐web studies: Non‐lethal stable isotope analyses substitute fin for muscle tissue with lipid correction
Author(s) -
Hicks Brendan J.,
Smith Dylan R.,
Pingram Michael A.,
Kelly David J.,
Fraley Kevin M.
Publication year - 2022
Publication title -
ecology of freshwater fish
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 55
eISSN - 1600-0633
pISSN - 0906-6691
DOI - 10.1111/eff.12647
Subject(s) - muscle tissue , fin , biology , fish fin , fish <actinopterygii> , isotope analysis , food web , zoology , extraction (chemistry) , freshwater fish , chloroform , fishery , ecology , anatomy , chemistry , trophic level , chromatography , materials science , composite material
Abstract Aquatic food‐web studies involving fish and using stable isotope analysis typically sample fish white muscle, which generally requires the fish to be euthanised. Alternatively, fin tissue can be sampled non‐lethally, avoiding the need to euthanise an animal to obtain what is usually a relatively small tissue sample. We set out to develop equations for converting δ 13 C and δ 15 N values from derived non‐lethally sampled fin tissue to equivalent white muscle tissue, for use in food‐web studies. We explored δ 13 C and δ 15 N values of paired fin‐clips and white muscle from two species of anguillid fishes, the endemic longfin eel ( Anguilla dieffenbachii ), and the Australasian shortfin eel ( A. australis ), sourced from multiple studies spread throughout New Zealand. We also examined the effect of lipid extraction on δ 13 C and δ 15 N, which reduced variability of δ 13 C when compared to untreated samples. We were also able to estimate δ 13 C values of equivalent lipid‐extracted muscle samples directly from untreated fin. For δ 15 N, paired untreated fin and muscle values were not statistically different so fin δ 15 N can be used as a direct estimate of muscle δ 15 N. Solvent lipid extraction with a methanol–chloroform mixture, however, altered δ 15 N values and increased variability, so should be avoided. We present equations to estimate lipid‐corrected δ 13 C values of muscle tissue for use in stable isotope studies of freshwater anguillids, avoiding euthanasia. Our results demonstrate that δ 13 C and δ 15 N values can be accurately derived from non‐lethally obtained fin clips, reducing unnecessary mortality in fish species of conservation concern.