Insight into the dietary preferences of adult European seabass (Dicentrarchus labrax) and thicklip grey mullet (Chelon labrosus) in the Dutch Wadden Sea through bulk stable isotope analysis
Mayorga Paz, Sofia
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Here, we aim to provide new insights into the diet of adult C. labrosus and D. labrax caught from summer to autumn in the Dutch Wadden Sea through bulk δ¹³C and δ15N tissue stable isotope analysis. Our stable isotope mixing model reveals that for D. labrax, flatfish sp. are the largest contributors to their diet, followed by Clupea harengus, Carcinus maenas, and Cragnon cragnon. For C. labrosus, their main prey items appear to be the macroalgae Ceramium rubrum, followed by Corophium sp., and green microphytobenthos. For both fish species, the prey preferences derived from this study’s stable isotope mixing models differ from those obtained from stomach content prey frequency analysis from the same sampling group. This could be a result of the temporal differences in the data retrieved between the techniques and the partially migratory nature of both fish species, amongst other reasons discussed. A comparison in the stable isotope values between D. labrax caught in three regions in the Dutch Wadden Sea - Terschelling, Balgzand, and Eierlandse Gat - reveals their diet is more similar between Eierlandse Gat and Terschelling in comparison to that in Balgzand. Our results also show D. labrax and C. labrosus length and sex had a significant influence on tissue δ13C values, but not on δ15N values. This suggests similar trophic level feeding but differing spatial foraging habitats between fish of differing lengths and sexes. A secondary aim of this study was to determine whether the dorsal fin stable isotope signature was more correlated to that of the species’ liver or muscle SIA. Fin tissue is preferable for SIA over liver or muscle tissue because the non-lethal nature of fin tissue collection means it can be applied for the diet analysis of tagged fish. For both fish species, fin tissue δ¹³C and δ15N were more correlated to that of muscle than liver tissue.