Stable-isotope analysis reveals the importance of soft-bodied prey in the diet of lesser spotted dogfish Scyliorhinus canicula

This study examines the diet of lesser spotted dogfish Scyliorhinus canicula, one of the most ubiquitous predators of European coastal waters. This species is of increasing ecological significance as other large predatory fish decline as it has known interactions with fisheries. Scyliorhinus canicula diet was investigated in Irish coastal waters during June and July 2014 using both stomach-content analysis and δ¹³C and δ¹⁵N stable-isotope ratios. Prey contribution to the diet from dual stable-isotope data was estimated using Bayesian mixing models. It was found that only stable-isotope analysis provided a time-integrated picture of the diet of S. canicula and allowed for a new estimation of their trophic position. Trophic positions from stomach-content analysis within the present study and previous studies were found to be higher than revealed by isotopes. Stomach-content analysis could not reveal the importance of soft-bodied animals in the diet of these fish, however this approach remains a valuable tool to understand the potential prey spectrum in advance of isotope analysis and allows for a better resolution down to species level. The results highlight a greater variety in the diet of this important predator and the benefit of taking a multidisciplinary approach in dietary studies.