By Tracy Brighten  September 2014

The set net ban zone will only be extended if Maui dolphins are seen beyond the protected area, but the chance of seeing dolphins is slim while habitat is unprotected

The campaign to save the critically endangered Maui, endemic to New Zealand, has escalated into an international affair. While environmental groups, marine scientists, the Ministry for Primary Industries and the New Zealand seafood industry are caught in a blame game, with the Department of Conservation mediating, cause of dolphin death is crucial.

DoC sends all Maui and Hector’s dolphins that are intact enough for analysis to Massey University, where Veterinary Pathologist Dr Wendi Roe performs the post-mortems.

As Roe dissects a savoury muffin, her lunch between meetings, she apologises before getting straight into the discussion on post-mortems.   Roe acknowledges the difficulty in identifying bycatch victims.

“There’s nothing specific, that you can say ‘that animal has drowned in a fishing net’… there’s nothing you can see, no test that you can do, that is 100 percent diagnostic of drowning.”

Even if a dolphin is caught in a net, Roe makes sure there is no other explanation.

Roe is reflective. “When you see them come in they’re beautiful, and they’re intact, and that’s sad.” But she doesn’t get emotional about them. “As a species, yes, but not individuals.”

When a dolphin is on the table, Roe has a job to do.

As a pathologist, she’s interested in how they died. Information gleaned from an individual helps prevent others from dying. In her office, she keeps files of dolphin reports on her bookshelf and a tall filing cabinet dominates the wall behind her. A wall map plots colour-coded sightings from Kaipara Harbour to Hawera.

The Maui is a sub-species of the Hector’s dolphin that inhabits South Island. Up to 1.6m long, these tiny dolphins with distinct rounded dorsal fin are among the world’s smallest, and with numbers estimated at only 55 adults over one year old, Maui dolphins are also the world’s rarest.

According to pathology reports held by DoC, dolphin W12-16Ch was a young female Hector’s; a bycatch victim with ‘encircling linear impressions (net marks) over her melon on both sides, and short linear lacerations on the leading edge of the right flipper,’ but an otherwise healthy dolphin.

Considering Maui and Hector’s biology – a female does not reach reproductive maturity until 7 to 9 years old, giving birth to one calf every 2 to 4 years – the loss of a female is significant to species’ survival, particularly Maui dolphins with only 20 breeding females left.

The number of dolphins dying in gillnets is likely to be underestimated. There is no incentive for fishermen to report bycatch, because they risk further protective measures that will affect their livelihood. Beachcast dolphins are generally reported by the public, but as Roe points out, beaches are not busy during winter months. Bodies may be quickly washed away by storms.

However, in the joint DoC and MPI 2012 Maui’s Dolphin Threat Assessment, fishing-related activities were nonetheless identified as the main threat, causing 95.5% of human-related mortalities. The remaining 4.5% was attributed to oil and mining activities, vessel traffic, pollution and disease.

Otago University marine experts Liz Slooten and Steve Dawson predict functional Maui extinction within two decades. The population can sustain one death in 10-23 years, yet the estimated death rate from bycatch alone is 3-4 per year.

Nylon gillnetting is so fine it is almost invisible, and dolphins become entangled. Interviewed by journalist Zoe Helene, Slooten describes what happens.

“A dolphin caught in a net struggles madly to try to escape. At the end of this struggle, the dolphin suffocates. It would take up to five minutes or so to die.”

Like humans, dolphins are social mammals. Slooten recalls, “We’ve seen one dolphin that had died in a gillnet that was covered in fresh toothrakes, many of which were bleeding. It seems that the other dolphins in the group tried to get this dolphin out of the net and failed.”

While acknowledging that the Maui’s dolphin Threat Management Plan revision in 2013 provides some extra protection from set nets, Forest & Bird Advocacy Manager Kevin Hackwell wants more. “The set net ban needs to be extended to all regions where these nationally-critical Maui’s dolphins are found. That includes all harbours and offshore to the 100m depth contour.”

There is international support too. At the International Whaling Commission meeting in September, 26 countries voted for total protection of Maui dolphins from fishing-related threats.

But resistance is strong. New Zealand’s fifth largest export earner, the seafood industry is a dominant player in the conservation game. In January’s contribution to The Fishing Paper, Seafood New Zealand is critical of protection zones in the absence of sightings. “The government has brought in yet more fishing restrictions to protect the pods of phantom Maui’s said to be resident off the Taranaki coast.”

They argue that fishing has a temporary impact on the environment, unlike farming’s permanent impact. But extinction is permanent and dolphin numbers are decreasing as the debate continues.

While the prospect of Maui dolphin extinction is unthinkable, Roe is looking beyond Maui at Hector’s swimming in their wake.

Since the 2012 Threat Assessment, research led by Roe published in Veterinary Parasitology in 2013, identifies another threat. Roe examined Toxoplasma gondii infection in Hector’s and Maui dolphins received by Massey between 2007 and 2011. Toxoplasmosis was identified as the cause of death in 7 of 28 dolphins, including 2 of 3 Maui dolphins. Studies on other species have identified indirect effects on populations, through changes in behaviour, reproduction, and predation risk.

Roe has been frustrated by the slow acknowledgement of the role of disease in declining populations. She smiles and nods at the suggestion that her research hasn’t had as much publicity as bycatch research, and explains that a lot of the research on dolphins worldwide may be biased.

“There are lots of people who research because they want to prove that they’re all dying in the fishing industry, or they want to prove that none of them are dying in the fishing industry.”

Her research was initially seen to excuse the fishing industry by directing the focus away from fishing-related mortality towards toxoplasmosis as the killer.

Roe points out that her findings relate only to dolphins washed up on the beach. She supports scientists’ findings on fishing impacts, but is keen to see disease mortality included in population modelling.

“I strongly believe we need to have strict controls on fishing zones and fishing nets, but the situation is even more important than we thought, because there’s more than one thing killing them.” Roe’s voice is soft, but authoritative.

When asked about Government attitude to Maui extinction, Primary Industries Minister Nathan Guy is clear in his written response. “Our position is that if there are sightings beyond the protected area then we will review the boundaries, but in 900 fishing trips, there have been no observations of Maui dolphins in these areas.”

The observer program on commercial fishing boats leaving Taranaki is well-intentioned, but watching murky coastal waters for tiny dolphins must require uninterrupted concentration and 20/20 vision.

Barbara Maas, NABU International’s Head of Endangered Species Conservation, criticises economic-driven decisions on protection zones that “reflect fishing interests rather than match Maui’s dolphin distribution.” Maas recently told Agence France-Press that having exhausted the scientific arguments, NABU, supported by 100 conservation groups, is proposing a boycott of New Zealand seafood.

Roe is not interested in extremist action, but believes collaboration is key to Maui and Hector’s dolphin conservation. She is involved in the Maui’s dolphin Research Advisory Group, a DoC and MPI initiative that held its first meeting last June. Including representatives from central government, regional councils, the fishing industry, environmental groups, scientific researchers, and iwi, the aim is to inform Maui conservation decisions through further research and population monitoring.

Roe’s current research is to identify how toxoplasma gondii is transmitted to dolphins. The most likely route into the marine environment is via contamination of fresh-water run-off. Oocysts, or spores, carrying the parasite and shed in cat faeces can contaminate coastal waters via feral cat populations, and storm water via domestic cat populations. Hector’s and Maui dolphins forage in harbours and estuaries and could ingest oocysts from water, or from eating fish and squid.

Declining to speculate about Maui survival, Roe sees their plight as a warning for Hector’s.

“I’m probably a little bit back-to-front on this,” she says, believing resources are best directed at looking after those there are more of.

It may be too late for Maui dolphins with our Government fixed in its position on protection zones like the set nets trapping them, but their endangered relative, Hector’s, could pull through.

“There are lots of lessons we can learn about what we should be doing now. It would be nice to react before there are 55 left.”

Note: DoC now uses “Maui”, but “Maui’s” has been preserved in quotes, document and group names

Image credit: S. Dawson (from NABU International website)