Data from: Stable isotopes reveal the effect of trawl fisheries on the diet of commercially exploited species

Bottom trawling can change food availability for benthivorous demersal
species by (i) changing benthic prey composition through physical seabed
impacts and (ii) by removing overall benthic consumer biomass increasing
the net availability of benthic prey for remaining individuals. Thus
trawling may both negatively and positively influence the quantity and
quality of food available. Using δ13C and δ15N we investigated potential
diet changes of three commercially exploited species across trawling
gradients in the Kattegat (plaice, dab and Norway lobster (Nephrops)) and
the Irish Sea (Nephrops). In the Kattegat, trawling affected primarily the
biomass of benthic consumers, lowering competition. Nephrops showed
significant positive relationships for δ13C and a domed relationship for
δ15N with trawling. In the Irish Sea, intense trawling had a negative
effect on benthic prey. δ13C and δ15N thus showed the inverse
relationships to those observed in the Kattegat. Plaice from the Kattegat,
showed a significant relationship with trawling intensity for δ13C, but
not for δ15N. No relationship was found for dab. Changes of δ13C and δ15N
correlated with changes in condition of species. The results show that the
removal of demersal competitors and benthos by trawling can change the
diets of commercial species, ultimately affecting their body condition.