Debris in the diet of the loggerhead sea turtle Carreta Carreta L. in the northern Adriatic Sea

Abstract

Analiziran je sadržaj probavila 49 glavatih želvi, koje su pronađene uginule u sjevernom Jadranu, u teritorijalnom moru Hrvatske i Slovenije u razdoblju od 2001. do 2004. godine. Dužina karapaksa istraživanih životinja iznosila je između 25.0 i 79.2 cm (srednja vrijednost: 42.2 ± 11.6 cm). Iz sadržaja probavila izoliran je krupni otpad. Nakon sušenja na zraku i vaganja, izoliranim uzorcima je izmjerena veličina te su razvrstani po skupinama. Krupni otpad je utvrđen u probavnom sustavu 17 želvi (34.7%). Pronađene su četiri vrste otpada: plastika, konop, stiropor i uže, od kojih je najveći dio bio proziran ili bijele boje, a zabilježen je u probavnom sustavu 64.7% želvi. Plastika je bila najučestalija, a utvrđena je kod 11 životinja (64.7%). Zabilježene su vrlo male količine otpada, a raspon suhih masa se kretao između < 0.01 i 0.71g. Na temelju dobivenih rezultata se može pretpostaviti kako prisutnost krupnog otpada u probavnom sustavu analiziranih jedinki nije bila direktan uzrok njihova uginuća. Ipak relativno visoka učestalost i mogući subletalni učinci unosa otpada, te oportunistički način ishrane glavate želve i značaj sjevernog Jadrana kao važnog pridnenog staništa ukazuju na činjenicu kako je smanjenje unosa antropogenog otpada, posebice plastike, u ekosustav Jadrana jedan od preduvjeta pravilne zaštite populacije glavatih želvi koje obitavaju u istraživanom području.We analyzed the diet composition of 49 loggerhead sea turtles found dead in the northern Adriatic Sea (Croatia and Slovenia), in the period between 2001 and 2004. Curved carapace length of loggerheads ranged from 25.0 to 79.2 cm (mean: 42.2 ± 11.6 cm). The anthropogenic debris was isolated from the digestive tract contents. Debris samples were later air dried, weighted, measured and divided into groups. The anthropogenic debris was found in the digestive tract of 17 loggerheads (34.7%). Four types of debris were found: plastics, ropes, styrofoam and lines. Most of the ingested debris was transparent or white colored and was found in 64.7% of turtles. Plastic was the most frequent type of debris, recorded in 11 turtles (64.7%). The quantities of the debris found were very small, and the range of dry mass was between < 0.01 and 0.71 g, which indicates that the ingestion of anthropogenic debris is not the direct cause of death of the analyzed turtles. Considering relatively high frequency of occurrence and possible sublethal effects of debris ingestion, together with the opportunistic feeding nature of this species and the significance of the northern Adriatic as an important benthic feeding habitat, it is important to minimize the input of debris, especially plastic, into the Adriatic Sea. That is one of the prerequisites for the effective conservation of the population of loggerheads that inhabit the studied region