Experimental determination of tissue turnover rates and trophic discrimination factors for stable carbon and nitrogen isotopes of Arctic Sculpin (Myoxocephalus scorpioides): A common Arctic nearshore fish

Rapid environmental changes occurring in the Arctic nearshore are expected to have significant effects on food web structures. Land-fast ice cover limits the effectiveness of monitoring methods during winter months, precluding understanding of how seasonal Arctic nearshore food webs operate. Tissue-dependent stable isotope analysis (SIA) offers an efficient and cost-effective approach to monitoring changes in food webs during ice-covered months but requires controlled laboratory experiments to determine isotopic turnover rates and trophic discrimination factors (TDFs) of different tissues. We propose that Arctic Sculpin (Myoxocephalus scorpioides) be used to investigate Arctic nearshore trophodynamics given its opportunistic feeding habits and consistent residence within nearshore Arctic habitats. We present the first tissue-dependent SIA experiment on an Arctic marine fish species and show that δ15N values of fin (or liver) and muscle of Arctic Sculpin may be used to identify shifts in low-trophic-level resource availability between 56 and 122 days before sacrifice. Furthermore, TDFs were determined for carbon isotopes (1.87‰), but results for nitrogen (1.23‰ to 3.23‰) suggest that TDFs in Arctic fish may be highly dependent on lipid content of their diet. We observed similar turnover rates between liver and fin tissues (56 and 58 days, respectively), and suggest it may not be necessary to sample both, making it possible to use Arctic Sculpin for tissue dependent analyses with potentially non-lethal sampling of fin and muscle tissues. The use of Arctic Sculpin as an indicator species can increase the understanding of food web structure and aid in monitoring changes to lower-trophic level prey availability as ecosystem dynamics are affected by climate change.