Marine mammal depredation and pelagic longline fishery: second trial to assess the efficiency of a scaring mitigating device in Saint-Paul Bay (Reunion Island), March – May 2011

There is good evidence that cetaceans use their sight and their echolocation abilities to locate the gear and/or the boat, follow them and depredate the fish caught. In order to mitigate depredation events and then reduce interactions between toothed whales and longline close to the gear, we propose to develop the physical protection of capture. The goal of this study is to test the efficiency of scaring devices protecting physically catches and frightening predators. The development of those devices ensue from two preliminary surveys undertaken in Seychelles in 2007 and 2008, and aiming at testing the efficiency of two older devices regarding physical protection of capture on a commercial longliner (Rabearisoa et al, 2010). In August 2010, as a first step of those experiments, we worked at a small scale by conducting surveys in Saint-Paul Bay, located in the south-western of La Reunion Island (Rabearisoa et al, 2010). In March and May 2011, we improved our devices and we worked at a larger scale in the same study area. We tested those devices on two coastal species of small delphinids, the bottlenose dolphin (Tursiops aduncus) and the spinner dolphin (Stenella longirostris), which are known to be resident within the study area (Dulau-Druot et al, 2008).