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Trophic partitioning between abundant demersal sharks coexisting in the North Aegean Sea

2019; Cambridge University Press; Volume: 99; Issue: 5 Linguagem: Inglês

10.1017/s0025315419000110

1469-7769

Emre Yemışken, Joan Navarro, Manuela G. Forero, Persefoni Megalofonou, Lütfiye Eryılmaz,

Identification and Quantification in Food

Abstract We examined the feeding ecology (diet, trophic width and trophic position) of five demersal shark species ( Mustelus mustelus Linnaeus, 1758, Galeus melastomus Rafinesque, 1810, Scyliorhinus canicula Linnaeus, 1758, Scyliorhinus stellaris Linnaeus, 1758, Squalus blainville , Risso, 1826) coexisting in the north-eastern Aegean Sea (around Gökçeda Island) by combining stomach content and stable isotope analyses. The results indicate clear differences in diet between the five sharks. Cephalopods were mainly found in diet of S. stellaris and M. mustelus and the stomachs of G. melastomus , S. canicula and S. blainville included fish. S. blainville showed the highest trophic position in respect of stable isotope analysis (TP sia = 4.89) around Gökçeada Island. It was followed by G. melastomus (TP sia = 4.57). Direct isotopic values (both stable nitrogen and carbon) and isotopic niche width based on the Standard Ellipse Area (SEA) clearly differed among the five shark species. In particular, S. blainville was isotopically segregated from the other shark species studied, showing a narrow isotopic trophic niche and higher trophic level. In contrast, M. mustelus had the widest trophic niche of the five species studied. The niche width of S. stellaris was narrower than M. mustelus and S. canicula but wider than S. blainville and G. melastomus . SEA showed that G. melastomus has a specialized feeding strategy in the area. There is no overlap between S. canicula and S. stellaris in trophic width.