Habitat and resource segregation of two sympatric seals in the North Sea

• Published in: Science of The Total Environment
• Main Authors: Damseaux, France, Siebert, Ursula, Pomeroy, Patrick, Lepoint, Gilles, Das, Krishna
• Other Authors: FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2021
• Subjects: Harbour seal; Grey seal; marine mammals; stable isotopes; mercury; selenium; sulphur; Germany; Scotland; Halichoerus grypus; Phoca vitulina; Life sciences; Environmental sciences & ecology; Aquatic sciences & oceanology; Sciences du vivant; Sciences de l’environnement & écologie; Sciences aquatiques & océanologie; harbour seal
• Online Access: https://orbi.uliege.be/handle/2268/251409; https://orbi.uliege.be/bitstream/2268/251409/1/2020%20Preproofs.pdf; https://doi.org/10.1016/j.scitotenv.2020.142842

peer reviewed In the North Sea, sympatric grey and harbour seals may compete for food resources impacted by intense fishing activities and a recent increase of seal populations. In order to reduce inter-specific competition, sympatric species must segregate at least one aspect of their ecological niches: temporal, spatial or resource segregation. Using isotopes and Se and Hg concentrations, the foraging resources of grey seals and harbour seals and the potential competition between these species in the North Sea was studied. δ13C, δ15N and δ34S values were combined with the concentrations of Hg and Se in blood samples of harbour and grey seals from the North Sea. Blood samples were collected on 45 grey seals and 37 harbour seals sampled along German and Scottish coasts. This multi-tracer approach showed spatial and resource partitioning within grey and harbour seals. Data indicated the offshore foraging distribution of grey seals as reflected by the lower δ15N values and T-Hg concentrations and higher Se concentrations, and the inshore foraging distribution of harbour seals because of higher δ15N values and T-Hg concentrations and lower Se concentrations. The SIAR mixing model revealed a more selective diet of grey seals compared to harbour seals, and the importance of sandeels in grey seal diet reflected by their high δ34S values. Lastly, diet ellipse overlaps between grey seals and harbour seals sampled along the German coasts suggested a potential sharing of food resources, possibly due to the increase number of grey seals number in this area during the foraging season - all year except breeding and moulting periods. The multi-tracer approach provided a more robust discrimination among diet resources and spatial foraging distributions of grey seals and harbour seals in the North Sea.