Diet composition of the spiny dogfish (Squalus acanthias L.) in the northern Adriatic Sea

Jusufovski, Dunja (2010) Diet composition of the spiny dogfish (Squalus acanthias L.) in the northern Adriatic Sea. Diploma thesis, Faculty of Science > Department of Biology.

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We analyzed diet composition of 157 spiny dogfish sampled by a bottom trawl, during a period from 2005 to 2007, in an area which occupies the aquatic ecosystem of Kvarner and Zadar, between 44°91’ i 43°59’ N and 14°06’ i 14°49’ E. Total body length of the samples ranged from 26.1 to 112.0 cm (mean = 57.51, SD = 20.3). Caught sharks underwent morphometric analysis including digestive tract content sampling which was afterwards preserved in 75% ethanol. Prey items were isolated from every stomach content and identified, also grouped in systematic categories and weighed. We recorded 6 prey groups in food remains: sea snails (Gastropoda), bivalves (Bivalvia), cephalopods (Cephalopoda), polychaetes (Polychaeta), crustaceans (Malacostraca) and ray-finned fish (Actinopterygii). The highest ranked prey groups included ray-finned fish with 68.3% of total wet weigth and 78.3% of occurence, and squid with 23.0% w.w. and 14.6% of occurence. Other prey groups represent altogether 8.7% of total wet weight. We noted a positive correlation between total body length (TBL) and total wet weight (rs = 0.247; p = 0.002), and also, a decrease in weight percentage of ray-finned fish (rs = - 0.278; p = 0.002) with an increase of TBL. There were no statistical significant differences in the diet between seasons. Analysis of the diet between sexes showed statistical significant differences in weigth and weigth percentage of ray-finned fish (p < 0.01) and in the diet between juvenile and adult dogfish, where the percentage of ray-finned fish was considerably larger in the diet of juvenile sharks in comparison to the diet of adult sharks. Temporal and TBL distribution of samples showed seasonal use of the researched area and also, its role as a critical habitat of the spiny dogfish in the northern Adriatic Sea.

Item Type: Thesis (Diploma thesis)
Keywords: Elasmobranchii, sharks, diet, Adriatic Sea
Supervisor: Lacković Venturin, Gordana
Date: 2010
Number of Pages: 43
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 03 Sep 2014 12:41
Last Modified: 18 Sep 2014 08:15

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