Fishing nets could wipe out dolphin populations

Washington, Oct 20 (IANS) Fishing nets often trap so many dolphins around the world that their numbers are falling below levels where they can maintain their populations, as shown most recently by a study in New Zealand. The number of Hector's Dolphins caught in commercial nets is 10 times above sustainable levels, according to a new analysis by Otago University.

Hector's dolphins are of particular significance, as they are only found in New Zealand. The main threat to the species is entanglement in fishing gear, in particular gillnets.

National Institute of Water and Atmosphere (NIWA) New Zealand estimates that 110-150 Hector's dolphins have been killed each year during 2000-2006.

Hector's dolphin populations have been seriously depleted as a result of fishing, to less than a third of original population size, with the North Island population worst affected at less than 10 percent of its original size.

Liz Slooten and Steve Dawson, associate professors at Otago, used the Potential Biological Removal (PBR) method, developed by the US National Marine Fisheries Service, to determine the level of human impact on marine mammal populations.

If the recent level of bycatch were to continue, said Slooten, Hector's dolphins are expected to decline to around 5,000 individuals over the next 50 years, according to an Otago University press release.

The results of this analysis are consistent with population viability analyses carried out by scientists, the fishing industry and the University of Otago.

Society for Marine Mammalogy, Scientific Committee of the International Whaling Commission and IUCN have pointed out that there is ample evidence on which to base effective protection measures for Hector's dolphin.

Slooten recommended that dolphins be protected from mortality caused by fisheries by changing to more selective, sustainable fishing methods.

'This would have benefits not only for Hector's dolphin conservation but also for other dolphin species and seabirds caught in these fisheries, and in the long term for the fishing industry itself,' she said.