Preliminary estimate of incidental mortality of Commerson's dolphins (Cephalorhynchus commersonii) in an artisanal setnet fishery in La Angelina Beach and Ría Gallegos, Santa Cruz, Argentina

The Commerson's dolphin, Cephalorhynchus commersonii, is perhaps the cetacean species most impacted by fisheries in the coastal waters of southern South America, south of 41°S. Between January 1999 and February 2000, 66 Commerson's dolphins were found dead on the coasts of La Angelina and Ría Gallegos, and at least 37 of the ones at La Angelina beach (51°20'S, 069°02'W) were caught incidentally. These captures occurred in gill nets that were set in waters shallower than 15m and mainly for Patagonian blenny (Eleginops maclovinus), silversides (Odonthestes nigricans) and parona leatherjack (Parona signata). The season for set net fishing, extending from the end of August to mid February, overlaps with the breeding season (November-February) of Commerson's dolphins, which is also when this species moves inshore. The estimated catch per unit of effort (CPUE) for gillnets in the area of La Angelina was 0.229 dolphins x (1,000m of net x set)-1. By extrapolation, the estimated total by-catch during the 1999/2000 fishing season in the region of La Angelina and Ría Gallegos was 179 dolphins (SD = 18.8; CI = 141 - 212). Although no abundance estimation of Commerson's dolphins in this region is available, the estimated level of bycatch is concerning. Recommendations for action to mitigate and further document the impact of set gillnets are presented