MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps13030

Ontogenetic trends in resource partitioning and trophic geography of sympatric skates (Rajidae) inferred from stable isotope composition across eye lenses

Samantha J. Simpson*, David W. Sims, Clive N. Trueman

*Email: samantha.simpson85@hotmail.co.uk

ABSTRACT: Resource partitioning is expected in sympatric assemblages of predators as a mechanism that reduces competition between individuals of different species or age classes, which in turn can affect population and community interactions as well as resource distribution and availability. However, for species such as benthic skates (Rajidae), whose juveniles are cryptic and not easily sampled by traditional survey methods, there is a knowledge gap concerning the spatial and trophic ecology during early life stages. The eye lenses of vertebrates grow over their lifetime providing a chronological biochemical record that can be used to infer differences in diet and/or foraging location (trophic geography) throughout the ontogeny of the animal. For the first time, eye lenses of four sympatric Rajidae species from the northeast Atlantic were successfully used to recover stable isotope life histories for individual skates. Isotopic separation among species and across life stages within species suggests that habitat partitioning and differences in trophic ecology are present throughout ontogeny. Isotopic data imply that adults are separated from juveniles both spatially and in terms of their diet and the four species appear to partition resources more than expected based on previous studies.