The analysis of stomach contents is a pivotal tool for understanding the trophic ecology of marine predators, predator-prey interactions, and the indirect occurrence of marine litter within food webs. This study investigates the diet of the small-spotted catshark Scyliorhinus canicula, sampled in the northern Ionian Sea during the 2025 MEDITS International Bottom Trawl Survey.

A total of 63 stomachs were examined ranging from 130 to 540 mm in total length (TL). Specimens were categorized into two size-classes based on maturity: juveniles ( 400 mm TL, n=36) and adults ( 400 mm TL, n=27). For each individual, biometric data, sex, and maturity stage were recorded. Prey items were identified to the lowest taxonomic level, and their dietary contribution was evaluated using the Prey-Specific Index of Relative Importance (%PSIRI). Ontogenetic dietary shifts were tested via the Morisita Index, while the Trophic Level was estimated combining %PSIRI with FishBase baseline values.

No empty stomachs were recorded, showing mostly medium-high fullness. The trophic spectrum was highly diversified, comprising benthic and benthopelagic prey. Overall, the diet was dominated by Mollusca (31.85%), Teleostea (25.45%), and Decapoda (16.62%), followed by Annelida (8.92%), unidentified Crustacea (6.89%), and Euphausiacea (5.21%). A high Morisita index (0.746) indicated significant dietary overlap between life stages, confirming substantial homogeneity in the trophic niche. The estimated trophic level (4.05 ± 0.40) characterizes S. canicula as a specialized secondary predator. Interestingly, plastic items were found in four juvenile stomachs, accounting for 2.43% PSIRI in immature specimens and 1.39% overall.

Although litter contribution remains low, its exclusive ingestion by juveniles could be related to the spatial overlap with high-litter accumulation zones or to an opportunistic feeding habit, but it needs to be better explored. These findings enhance our understanding of S. canicula's trophic role in the Ionian Sea and highlight the importance of marine litter monitoring across the marine food web.