engleski

(By)catch of spiny dogfish (Squalus acanthias) in the north-eastern Adriatic trawl fishery

The spiny dogfish belongs to the long-lived, slow-growing and late maturing group of marine megafauna, with the lowest reproductive capacity and growth rates known for any shark species. Although naturally abundant, it is one of the most vulnerable species of sharks to over-exploitation. Stock assessments documented declines of >75% for some Atlantic populations, and the species is globally listed by IUCN as Vulnerable. The spiny dogfish is one of the demersal shark species commercially fished in the Adriatic Sea. In order to quantify its exploitation in the northeastern Adriatic, we carried out on-board observations on bottom trawls, in area between 44°32’ and 43°44’ N, and 15°05’ and 14°40’ E, from April 2005 – January 2007. We surveyed 224 hauls, from depths between 45 – 84 m. In total, 252 individuals were collected, with TL ranging from 19.5 – 112.5 cm (mean: 55.2 ± 24.5). The mean CPUE (number of sharks/hour haul) was 0.1837. In term of numbers of sharks, 46.4% of the catch was landed, with females accounting for 65.2% of landings. The mean TL and weight of individuals kept for sale was 80.9 ± 17.3 cm and 2, 125.2 ± 1, 815.6 g, respectively, and were both significantly larger (p < 0.001) than those discarded (39.2 ± 10.6 cm and 247.1 ± 210.8 g, respectively), with cutoff TL = 50 – 60 cm. The survival of discarded juveniles is unknown. Life history studies have shown that spiny dogfish populations are very sensitive to harvest of adults, which means that the current level of harvest may not be sustainable. Future research should focus on trends in shark CPUE and sizes to determine if the exploitation rate is too high.

sharks; fishery; Adriatric; Mediterranean; CPUE; bycatch; conservation

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