engleski

Stomach content analysis of the Atlantic bluefin tuna in Adriatic Sea

Atlantic bluefin tuna, ABT, (Thunnus thynnus) is one of the largest marine predators and an important target species for commercial and recreational fisheries. Studies of the feeding ecology are important for better understanding their trophodynamics and the food webs in which they play important role. Stomachs contents of 24 ABT, including both juveniles and adults (weight range from 8 to 80 kg) collected in the eastern Adriatic Sea, were analysed by morphological inventory and DNA metabarcoding. Preliminary DNA metabarcoding tests were performed on five individuals. DNA was extracted from stomach swab and homogenate of stomach contents using a commercially available DNeasy Blood & Tissue kit (Qiagen). Partial fragments of two gene regions (cytochrome c oxidase subunit I (COI) and the ribosomal 18S-V1V2 region) were amplified using universal metazoan primers and commercially sequenced on Illumina MiSeq platform. Molecular identification of prey using DNA metabarcoding approach resulted with greater prey diversity than obtained using morphological approach. A large difference in sequencing reads between the two types of DNA samples, with most reads coming from tuna DNA in the case of the stomach swab was also noted. The most abundant prey species are small pelagic fish (~97%) and cephalopods (~3%). Noteworthy is that we also detected some demersal and gelatinous species such as Atlantic stargazer (Uranoscopus scaber), European hake (Merluccius merluccius), red mullet (Mullus barbatus), smallspotted catshark (Scyliorhinus canicula) and Salpa spp. These results suggest that ABT is an opportunistic feeder and that DNA metabarcoding can be a powerful tool for analysing the stomach contents of key marine predators.

DNA metabarcoding ; COI ; 18S ; morphological analysis ; Atlantic bluefin tuna

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