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Set net ban needed to protect Hector’s Dolphin

Published: Fri 4 Nov 2005 04:28 PM
4 November 2005 - Christchurch
Set net ban needed to protect Hector’s Dolphin
The Royal Forest and Bird Protection Society has repeated its calls for a national ban on set netting after the killing of four Hector’s dolphins in set nets at Neil’s Beach in South Westland’s Jackson Bay.
“This high level of human induced mortality cannot be sustained by a slow breeding and threatened species such as Hector’s dolphin. It puts the whole South Westland and West Coast Hector’s dolphin populations at risk,” Forest and Bird regional field officer Eugenie Sage said.
“New Zealand is well behind the rest of the world in continuing to permit such an indiscriminate fishing method with its deadly bycatch of dolphins, penguins, shags and other marine life.
“The use of monofilament set nets or gill nets in shallow waters is banned in many overseas countries including coastal states of the United States (California, Texas, and Florida), in England, Wales, Scotland, Italy and Greece. In Australia, the use of recreational set nets is banned, except in Tasmania,” she aid.
“In the absence of a national set net ban Fisheries Minister, Jim Anderton, should use his powers under the Fisheries Act 1996 to make Jackson Bay set net free, because of its importance as a nursery area for Hector’s dolphin mothers and calves,” she said.
“The survival of mature reproductive females is the most important factor influencing the population growth of Hector’s dolphin. Jackson Bay is one of only two known areas in South Westland regularly used by dolphin females and their calves”.
“The South Westland Hector’s dolphin population is at risk of decline from human induced mortality because of its small size, the species’ restricted home range, and slow reproductive rate. Females have a maximum of five to six calves in their lifetime,” she said.
Of the estimated 5,400 Hector’s dolphin on the South Island’s West Coast, only 170 are estimated to occur in South Westland between Makawhio Point and Milford Sound.
Background notes
Sections 11 (sustainability measures) and sections 15 and 16 (fishing related mortality) of the Fisheries Act 1996 give the Minister of Fisheries the power to ban set nets as a emergency or more permanent measure.
Researchers have calculated that the West Coast population of Hector’s dolphin as a whole could sustain fewer than 8 deaths per year due to additional human impacts, while the small South Westland local population could sustain less than 1 death every 5 years.
Research by Stephen Bräger between 1995 and 1998 indicates that Jackson Bay is a locally important area for Hector’s dolphins. Bräger’s survey data showed that up to 90 Hector’s dolphins use Jackson Bay at any one time and that pods can contain as many as 40 individuals.
Although large group sizes (10-50 animals) are not uncommon on the West Coast, their frequent occurrence in Jackson Bay suggests that it is a habitat favoured by Hector’s dolphins.
In many other cetacean species, coastal nursery areas are often sheltered sites, with low energy demands for the mother and calf. This may be why Jackson Bay is a favoured nursery area for Hector’s dolphins.
Dolphins have a small home range (c31 km of coastline on average from research at Banks Peninsula). A declining local population in South Westland is unlikely to be supplemented by individuals from adjacent local populations.
Jackson Bay is at the southern limit of the Hector’s dolphin distribution on the West Coast. Hector’s dolphins are rarely seen south of Jackson Head and are very uncommon in the deep waters of Fiordland. Research has shown that the South Westland population of Hector’s dolphin is distinctive and genetically different from Hector’s dolphin in Buller.
ENDS

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