A 'revised understanding' of the threat to Maui and Hector’s dolphins is being welcomed by the commercial seafood sector.

A 'revised understanding' of the threat to Maui and Hector's dolphins is being welcomed by the commercial seafood sector.

The scientific assessment, led by NIWA's Dr Jim Roberts and Quantifish, a quantitative fisheries science company, has identified toxoplasmosis, a microscopic parasite spread by cats as the main non-fishery cause of death, and responsible for killing nine Hector's and Maui dolphins recovered since 2007.

Seafood New Zealand chief executive Tim Pankhurst said the industry is playing its part to prevent dolphin deaths, particularly Maui of which only an estimated 60 remain. Hector's dolphins, while classified as endangered, are much more numerous, numbering around 15,000.

"The industry remains focused on preventing dolphin deaths. No Maui death has been attributed to commercial fishing since 2002 and that is because we have vast areas of ocean closed to trawling and set-netting in dolphin territory."

Over 6,200 square kilometres of coastal waters are closed to set net fishing activity and 1702 square kilometres to trawl fishing activity. In addition, there is almost 100 percent observer coverage in Maui territory. There is nearly 100 percent government observer coverage in the waters still fished. In set-net territory - from New Plymouth to Hawera - there is observer coverage 120 days per year, which equates to 95 percent coverage of all fishing. This would be 100 percent if more observers were available. In the trawl fishery from Kaipara Harbour to Hawera there is 600 days observer coverage each year, which equates to 90 percent of all fishing effort.

"It is heartening to see recognition that commercial fishing is not the most significant threat to the sustainability of the dolphins and with that, the opportunity to prevent further deaths," said Pankhurst.

Dr Roberts said; "the new assessment has significantly altered understanding of the relative risk to Hector's and Maui dolphins from commercial fisheries."

Pankhurst said blaming commercial fishing for Maui dolphin deaths was a default position for many fishing opponents but, as Dr Roberts points out, the numbers of dolphins dying from toxoplasmosis are likely to be much greater than commercial fishery deaths and may add up to hundreds each year.

Dr Roberts research also demonstrates that fisheries bycatch is not, under current conservation measures, sufficient to be the major driver of further population declines for both Hector's and Maui.

"The commercial fishing industry will continue to work to prevent dolphin deaths. However, we would like to see a more balanced dialogue around alternative threats. Addressing both recreational set-netting, which remains unregulated, and toxoplasmosis would be a great start."

NIWA's press release can be found here; https://www.niwa.co.nz/news/scientists-reach-new-understanding-of-main-threats-to-hectors-and-maui-dolphins