In search of prey: the occurrence of Alopias vulpinus in the northern Adriatic Sea and its interactions with fishery.

The common thresher shark, Alopias vulpinus, has shown a marked decline in abundance in the Mediterranean Sea. Through the analysis of long-term fishery time series (1966–2013), this study highlights that an important driver of the presence of A. vulpinus in the northern Adriatic Sea, one of the most exploited basins of the Mediterranean, is the abundance of its prey, the sardine Sardina pilchardus. From 1997-2013, an annual average of 14 thresher sharks was landed at Chioggia (Italy), the main fish market in the area, mainly from July to October. More than 75% of the landed thresher sharks were sexually immature, with some specimens weighing less than 10 kg, indicating that a high proportion of the catch was composed of small young and newborn individuals. These results support the occurrence of a nursery area in the northern Adriatic Sea, highlighting the need for proper management of A. vulpinus catch in this area.