Marine mammals interactions with tuna fishing activities in Indonesian seas

For decades, marine scientists have known that fisheries throughout the world result
in mortality for cetaceans (whales, dolphins, and porpoises). Incidental catch (also known as by-catch) in fisheries is considered the biggest threat to the survival of cetaceans globally. Migratory species such as cetaceans are exposed to various threats because they are nomadic.
From a conservation and management perspective, the level of protection given to cetaceans differs according to their geographical location. This study was conducted to determine the extent of by-catch in the study area and identify measures taken by fishers to minimize bycatch.
During a 20-day period, 222 fishers were interviewed in six locations - East Kalimantan,
North Sulawesi, Ternate, Morotai, Seram, and Biak - to identify the interaction between marine mammals and tuna fishing activities, particularly related with the usage of different fishing
gear and fishing practices. Twenty cetacean species from by-catch were identified by
respondents including three species of baleen whales and 17 species of toothed whales
(including dolphins). Results from this survey indicated that interactions between marine
mammals and tuna fisheries in Indonesian seas are primarily due to cetacean predation on tuna (e.g., pilot whales). To manage and minimize cetacean by-catch in the Indonesian seas, one of the recommendations from the authors of this study is the development of a Marine Mammal Mitigation Plan.