Cetaceans and western Indian Ocean tuna fisheries

Tropical tuna fisheries have expanded enormously in recent decades. Increased interactions with cetaceans are inevitable, and those in the western and central Indian Ocean are no exception. A new report from the region finds that there has been a widespread failure to monitor and manage cetacean interactions and bycatch in Indian Ocean tuna fisheries, and to develop and implement mitigation measures. The enormous, and still growing, gillnet capacity in the region should be of particular concern. The major gillnet fishing fleets are from the countries bordering the Arabian Sea: Sri Lanka, India, Pakistan, Iran, Oman and Yemen. It is estimated that at least 60,000 small cetaceans are taken annually by tuna gillnetters in this region. Illegal high-seas gillnetting is common. Purse seiners (mainly from France and Spain) regularly set on baleen whales (probably Bryde’s whale, Balaenoptera brydei); mortality rates are not known, but are probably in the 10s per year. Purse seiners report that tuna do not associate with dolphins in this region, but that is not true. Large yellowfin tuna do regularly associate with both pantropical spotted dolphins (Stenella attenuata) and spinner dolphins (Stenella longirostris) as well as with long-beaked common dolphins (Delphinus capensis). This discrepancy does not necessarily mean that purse seiners set on dolphins, but it does open it to question. There are also issues with the longline fisheries, where depredation (by both sharks and cetaceans) is a serious problem for some fishermen. There is a suggestion that some longline fishermen may be shooting cetaceans, especially false killer whales (Pseudorca crassidens).

The full report is available at: http://www.ipnlf.org/