New research shows that eliminating gill netting and trawling in 16 of the inshore fishing areas in New Zealand waters will be the most effective way of stopping Hector's Dolphin declining into extinction.
Once common in New Zealand coastal waters, Hector's dolphins have declined in number from about 26,000 in the 1970s (when set netting expanded dramatically) to about 7000 now.
The species is listed by the World Conservation Union as endangered. Only an estimated 111 individuals remain of the North Island sub-species, Maui's dolphin, which is critically endangered.
The University of Otago study, compared the effectiveness of four different management options.
The research, carried out by Department of Zoology Associate Professor Liz Slooten, considered the four options being examined by the Ministry of Fisheries and the Department of Conservation, who are putting together a threat reduction plan.
The analysis found that if the current management practice, option A (which includes two protected areas for the dolphins - one at Bank's Peninsula and one off the North Island's West Coast), or option B (extending the two existing protected areas to make them 100 per cent effective) was implemented, the numbers of Hector's Dolphins would continue to decline.
While option C – creating four large protected areas with fisheries mortality levels close to zero, had a predicted outcome of increasing dolphin population levels, but greater levels of mortality outside the protection zones.
The report concludes that option D – changing to selective, sustainable fishing methods that do not catch dolphins would give the dolphins the best chance of re-establishing their population.
Associate Professor Slooten says only option D shows a realistic promise of meeting national and international guidelines for marine mammal protection. “For example, under option D there is still only a 59 per cent chance of reaching half of the original population size by the year 2050 and even then several populations stay at very low levels for several decades.”
Associate Professor Slooten says the research shows that taking any of the three less assertive actions being considered by the Ministry of Fisheries would cause undue risk for the dolphin population.
Gillnets (and to a lesser extent trawl fisheries) are a serious threat to Hector's dolphins, she says. “The entanglement of dolphins in fishing gear is a nationwide problem that requires a nationwide solution.
“However, there is no need for fishing to stop. Fishing methods like long-lining, angling, surfcasting, other hook and line methods including trolling, using a kontiki raft to fish off a beach, fish traps, craypots, drag netting for flounder, spear fishing, jigging, hand gathering, or using fish attraction devices pose little if no risk to dolphins. Fishing with lines and hooks is one of the most traditional fishing methods and is very selective.”
An extra benefit of option D is that it will help to reduce the loss of seabirds and reef fish populations, she says.
Editor's Note: Original news release can be found here.