Promoting the use of non-lethal sample collection for analysing the trophic relationships of inshore flatfish populations using stable isotope analysis

Trophic studies on inshore flatfish populations usually rely on stomach content analyses and/or stable isotope analysis (SIA) of dorsal white muscle that involves the collection of samples from euthanised fishes. To promote the use of non-lethal sampling methods in inshore flatfish populations of relatively high intrinsic angling and/or ecological value, the applicability of using fin tissue and/or epidermal mucus as non-lethal alternatives to muscle in SIA studies was assessed for European flounder Platichthys flesus, plaice Pleuronectes platessa and common sole Solea solea. In all species, the results indicated that there were significant differences in the δ13C and δ15N values of dorsal muscle versus their fin and mucus samples. These significant differences were, however, predictable by linear regression, with regression coefficients produced for converting fin and mucus SI values to the equivalent muscle SI values. The use of combined data across the species also provided regression coefficients for converting fin and mucus SI to equivalent muscle values for flatfish populations more generally. These results indicated that there are tissue alternatives to dorsal muscle that can be applied to the SIA of flatfish populations, with these tissues able to be collected using non-lethal sampling methods. •Trophic studies on inshore fishes are generally based on destructive sampling.•Flatfish stable isotope (SI) studies tend to analyse muscle from euthanised fish.•Flatfish fin and mucus samples can be collected non-destructively.•Fin and mucus can be used as an alternative to muscle in flatfish SI studies.