Comparative analysis of feeding habits and dietary niche breadth in skates: the importance of body size, snout length, and depth

Resource partitioning among sympatric elasmobranchs in the central-western Mediterranean continental shelf

“…The species with a narrower bathymetric distribution belonged to the first group. Barbini et al (2018) observed a positive correlation between trophic niche breadth and size in skates ≤ 100 cm TL, suggesting that the increase in size could benefit individuals by allowing them to expand their prey range. Over 100 cm TL, the correlation became negative, maybe because larger individuals selected more energyrich prey.…”

“…In general, these species with a narrower bathymetric distribution, and occupying shallower waters, showed a more specialized trophic niche with respect to those distributed in a wider depth range. Barbini et al (2018) underlined a positive correlation between trophic and habitat niche range in batoid species, maybe due to the higher prey availability to those species that can exploit different habitats. Moreover, the levels of specialization found on the Sardinian continental shelf were higher than those reported for the same species in other areas worldwide (e.g.…”

“…Shifts in the feeding habits associated with ontogenetic development are well documented in elasmobranchs (Wetherbee et al 2012;Barbini et al 2018). However, comprehension of the consequences of changing dietary preferences with ontogeny on resource partitioning, species interactions, trophic level and, more generally, on the ecological role of these species in marine ecosystems is still lacking (Navia et al 2016).…”

Ecological specialization is associated with high conservation concern in skates (Chondrichthyes, Rajiformes)

“…amphipods, isopods and cumaceans), euphausiids and mysids, decapods and stomatopods, and polychaetes. We calculated an index of standardized diet composition to determine the proportion of each prey category in the diet of a species, because different dietary indices exist and more than one diet study was available for many species (Cort es, 1999;Ebert & Bizzarro, 2007;Barbini et al, 2018). To determine the dietary niche breadth for each skate species, we calculated Levins' standardized index of niche breadth (Krebs, 1989), using the standardized diet composition.…”

“…Skates are suitable to use as a case study to test this hypothesis because they are morphologically conservative (Ebert & Compagno, 2007) but their ecological traits differ widely (e.g. depth range, Dulvy et al, 2014; and feeding habits, Barbini, Sabadin & Lucifora, 2018). In a context of overexploitation, it is expected that skate species that differ in niche breadth are also different in vulnerability to population declines.…”