Liz Slooten and Steve Dawson use 23 years of research on Hector's and Maui's dolphins to rebuff claims that conservation efforts are misguided.
KEY POINTS:
Plans to protect Hector's and Maui's dolphins have led to some extraordinary claims in recent weeks. Having studied these dolphins since 1984, we thought we should answer some of them.
"The number of dolphin deaths has been exaggerated."
A repeated claim is that published estimates of dolphin
by-catch must be wrong because the Department of Conservation database of voluntary reports includes far fewer dolphin deaths. The by-catch record for Canterbury shows why these statements are misleading.
Voluntary reports of dolphin entanglements average two dolphins a year. However, using data from independent observers on fishing boats, Niwa estimates that around 30 dolphins a year are caught in the Canterbury gillnet fishery alone.
"Research showing that dolphin populations are declining is wrong."
This would mean that scientists at Otago University, Niwa and the fishing industry are all wrong, as their work indicates that Hector's dolphin populations numbered 21,000 to 29,000 in the early 1970s compared with fewer than 8000 now.
In the next 50 years, they are expected to decline to below 6000 if nothing more is done, or recover to around 15,000 if fishing deaths are eliminated.
"Maui's dolphins don't enter harbours and haven't been studied since 1987."
Since 1987 research by Auckland University, Otago University and DoC have included boat surveys, genetic sampling, aerial surveys (one is happening right now) and monitoring with acoustic data loggers (starting in 2004 and going on).
There have been several sightings and acoustic detections in the Manukau Harbour, beyond the protected area.
The other harbours have not yet been studied in detail, but reliable sightings have been made in three of the five.
"We need more information."
This is a standard catch-cry from industries causing health and environmental impacts, and sometimes echoed by agencies responsible for managing those impacts.
In fact, much more information is available for Hector's dolphin than for most other dolphin species.
For example Hector's dolphin is one of only two dolphin species in the world for which there is a robust estimate of total population size and one of three for which there is an estimate of adult survival rate.
About two years ago, as part of the development of the Threat Reduction Plan, DoC and the Ministry of Fisheries set up an advisory group and an expert panel. Both groups included representatives from the fishing industry, recreational fishers, the tourism industry, conservation groups, iwi and independent scientists. These groups agreed without difficulty that the most serious threat to the species is entanglements in gillnet and trawl fisheries.
We know exactly what the problem is and how to solve it.
"The economic cost is too high."
Fishing industry lobbyists argue that saving Hector's dolphin will cost hundreds of jobs and millions of dollars. These claims are unfounded. First, setnetting is not very important to the New Zealand economy, contributing a fraction of 1 per cent of total income from fishing. Secondly, the claim assumes that all these fishers would have to stop fishing. The more relevant figure would be how much less would they make if they change to fishing methods that don't catch dolphins. There is no need to stop fishing.
Moreover the change could be relatively painless. Most fishing boats in New Zealand that use gillnets already use other methods as well, including trawling, craypots and longlines.
What needs to be done?
DoC and MFish have recently released for public consultation a draft Threat Management Plan for the species. The public has been invited to comment on the plan. Option 3 is the only option in the draft plan that comes close to meeting national and international standards for marine mammal conservation, and that is to ensure population recovery
Fishermen themselves will benefit from using selective, sustainable fishing methods. There would be many advantages, not just for Hector's dolphin and other dolphin species but for a wide range of other species including non-target fish species and seabirds. In addition, there will be long-term economic benefits.
Dolphins: Worth more alive than dead
These dolphins are worth millions of dollars to the New Zealand tourism industry.
What is it worth for New Zealand to be seen internationally as a clean and green country that makes conservation decisions based on peer reviewed and published scientific data, rather than hearsay and political pressures? How much would it cost us if we lost that image?
* Liz Slooten and Steve Dawson are associate professors at the University of Otago.
