Microplastics ingestion by deep-water catsharks Galeus melastomus and Scyliorhinus canicula (Chondrichthyes) in the Tyrrhenian sea (Western Mediterranean Sea)

Nowadays plastic debris must be considered a ubiquitous element of marine ecosystems, distributed both in shallow and deep-water. Different diet studies suggest that shark and rays could be threatened by plastic ingestion. Blackmouth catshark, Galeus melastomus (Rafinesque, 1810) and lesser-spotted catshark, Scyliorhinus canicula (Linnaeus, 1758) are two abundant deep-water elasmobranchs, both opportunistic scavengers, whose feeding habits have been widely studied in overlaps and differences. The aim of our study is to verify any differences in frequency of plastic ingestion by the two species and to evaluate possible incidence according to the intra-specific variables. Samples result from a by-catch of professional fishing boat armed with trawl net for Giant red shrimps capture at depths between 400 m and 500 m. Morpho-anatomical data (total length, total weight, sex, maturity stage, weight of liver and gonads) were recorded for each individual. Stomach and intestinal contents were weighed before incubating separately in a 10% KOH digestive solution at 60 °C overnight, to remove biogenic material and identify plastic debris using a stereomicroscope. Nature of suspected items was determined using Fourier Transformed Infra-Red spectrometry (FT-IR). Preliminary results confirm that plastic ingestion occurs in both species and filaments-like are the most frequent items, without significant differences in the two catsharks. However, there is a greater variability in shape of plastics (sphere, fragment, film) ingested by G. melastomus than S. canicula. This probably reflects differences in feeding habits of the two species. The detection of plastics in the final part of the gastro-intestinal tract of both species seems to suggest that these animals can expel the plastics with the feces and no forms of gastric blockage have been observed. Studies are in progress to verify the magnitude of the observed differences between the two species and to better investigate the phenomenon.