Feeding habits of the Blackmouth Catshark (Galeus melastomus) from Central Mediterranean Sea, with emphasis on plastic ingestion.

The blackmouth catshark Galeus melastomus (Rafinesque, 1810) is one of the most abundant Scyliorhinidae in the Mediterranean Sea. Scavenger and opportunistic feeder, this species lives between 50 and 1400m depth from Norwegian sea to Senegal and in all the Mediterranean Sea. Although the vast distribution, little is known about the feeding habits, especially in the Tyrrhenian Sea. Specimens analysed in this study were obtained from October 2020 to August 2021. They came from five populations of the Tyrrhenian and the Ionian Sea at a mean depth between 40 and 700m. The main purpose of this work was to investigate the diet of the blackmouth catshark analysing the stomach contents. A total of 302 samples and 253 stomachs were collected and analysed. All the stomach contents were sub-divided in macro-categories and identified with the help of some taxonomic guide at the lower taxa possible. Crustacean like Parapeneus longirostris and Pasiphea sivado; Cephalopods like Heteroteuthis dispar, Todarodes sagittatus and Oynchoteuthis banksii and Osteichthyes, above all specimens of Mychtiophidae, were found. Plastic debris was found too among stomach contents. They were classified according to their colour (black, blue, green, grey, orange, red, yellow and white) and shape (fibres, fragments, film and sphere) in accordance with Eriksen et al., 2014 and Valente et al., 2019. Osteichthyes represented the most abundant item found in the stomachs, except for the population from Tuscany, where Crustaceans and Molluscs were dominant. Also for plastic debris, we observed significant differences between the population from Tuscany, where fibers were dominant, and the other populations, where fragments were more abundant. These differences could be explained with the different depths at which the blackmouth catshark populations live: the population of Tuscany, in fact, is the only one of depth, considering that it was sampled at -600 m.