The littlest dolphin and littlest planet

From Nine To Noon, 11:48 am on 20 July 2015

Kennedy Warne

Maui's dolphin.

Maui's dolphin. Photo: Earthrace Conservation/Liz Slooten (CC BY-NC-SA 2.0)

I attended a marine sciences conference last week, and heard the latest update on Maui’s dolphin from University of Otago dolphin expert Liz Slooten, and it was not pleasant listening.

If a movie were to be made about Maui’s dolphin, it could be called “Ocean’s Eleven,” because that’s roughly how many Maui’s dolphin mothers remain in the ocean. The latest population estimate is between 43 and 47 adults—less than half what it was a decade ago. The sex ratio in Maui’s dolphins is assumed to be 50:50, so that means perhaps 22-23 adult females, of which only half will be of reproductive age. So, about 11 mothers. And the number is declining all the time. The latest estimate of the number of dolphins being killed by fishing activities (commercial and recreational) is between 3 and 4 a year. To stop the population declining still further requires this human-induced mortality to drop to 1 death every 10 to 23 years!

We all know the story of “Old Blue,” the female black robin that reproduced her species out of the jaws of extinction, and the reason she could do that is that she was out of harm’s way on a predator-free island. Maui’s dolphins are very much still in harm’s way, because the government is reluctant to extend the current netting bans to cover the full range of the dolphins, which is to say from the coast to the 100-metre depth contour. Liz Slooten says less than 20% of the dolphins’ range is protected from gillnets and trawling, which are estimated to be responsible for 95% of Maui’s dolphin deaths.

Government and industry have said more research is needed to show the extent to which dolphins use their assumed range, but the scientific committee of the International Whaling Commission disagrees. In a report released last month, it says what is needed is not more research but immediate regulatory action. (And let’s be clear: often a call for “more research” can be a stalling tactic, or an excuse for inaction, as it has been with climate change.)

It’s hard not to conclude that we’re taking a pretty big risk with this animal, gambling that we can magically avoid the fishing-related deaths that will propel the subspecies into an extinction spiral—as happened with the baiji, the Yangtze River dolphin, which is now considered extinct. Like many marine mammals, Maui’s dolphins are not prolific breeders. Females start to breed at age seven and, on average, produce one calf every two years. So recovery of the population is a long-term process, and it can only start when fisheries mortality (and preferably all human-caused mortality) is reduced to zero.

Compare our government’s reluctance to take more aggressive protection measures for Maui’s dolphin with the decisive action Mexico just took over another extremely rare, tiny cetacean, the vaquita. Faced with a similar situation of fishing interests vs survival of a species, earlier this year the Mexican government introduced a two-year gillnetting ban covering the entire area the vaquita is known to occupy, in the upper Gulf of California, to be policed by the Mexican navy.

Part of the Mexican approach is to pay fishers to switch to vaquita-safe fishing gear. Difficult as that would be here—or anywhere—I wonder how seriously it has been considered. I was interested to learn that the number of commercial fishers that would be affected by a comprehensive net ban is relatively small. In 2007, the last time a survey was conducted, there were only eight commercial fishers who caught more than 6% of their total catch using gillnets or trawl gear in the affected area (off the west coast of the North Island), and an additional 120 fishers who used nets to catch 1-5% of their catch. Their combined catch was a quarter of the total fish caught on the North Island west coast.

And the point is, no one is arguing for a fishing ban, just a netting ban. Fishers are welcome to use lines, fish traps and other dolphin-safe fishing gear throughout the entire area.

A much greater number of recreational fishers use gillnets to catch fish in harbours in the region—harbours that are also frequented by Maui’s dolphins. Yes, there are longstanding social and cultural traditions concerning the use of set nets, but if the continuance of a species is at stake—and you can catch fish using another method, a less wasteful, indiscriminate method . . . well, do we want to see another baiji on our watch?

Is it feasible to pay fishers to change? I don’t know, but we’ve just had an example on land of a similar approach: funding a shift in how an economic activity is pursued to achieve an environmental good. I’m talking about the effort to reduce nitrogen levels in Lake Taupo. A combination of buyouts and spending from an $80 million fund to help farmers shift from dairying and to farm less intensively has proved effective, with farmers signing up three years ahead of the expected schedule.

Environment minister Nick Smith praised the Taupo strategy and said it is the sort of approach that will need to be taken for other waterways, and I agree with him. But it should also be considered for other situations where a demonstrable public good—or in Maui’s dolphin’s case an existential good—relies on a change in human activity.

The Pluto spectacle

Whenever there’s a hint of an aurora in New Zealand skies (always in the deep south—worse luck for this Aucklander) or a supermoon is rising, or an interesting conjunction of heavenly bodies occurs (Jupiter and Venus this month), the event makes headlines. The universe fascinates us—and so it should.

This last week it has been Pluto’s turn to shine. Maybe we have a soft spot for the littlest, farthest planet—or “dwarf planet” as it is now classified—but the images beamed Earthward from the New Horizons spacecraft have captured the world’s attention.

The last image of Pluto sent back by New Horizons before its closest approach to Pluto.

The last image of Pluto sent back by New Horizons before its closest approach to Pluto. Photo: NASA/APL/SwRI

A big surprise—and an understandable crowd favourite—was the revelation of a vast heart-shaped plain about 1600 km across, which is more than the distance from North Cape to Bluff. Rising out of one part of that plain (named Tombaugh Regio after Clyde Tombaugh, who discovered Pluto in 1930) are mountains almost as high as the highest peaks in the Southern Alps, but made not of rock but ice. Bear in mind that the average temperature on Pluto’s surface is -230 degrees C—cold enough to turn nitrogen, methane and carbon monoxide into a solid, and all these types of ice are present on Pluto.

The mountain ranges were promptly named after Tenzing Norgay. And it may not be long before a couple of Aotearoa/New Zealand names are applied to Pluto’s landscapes. A few months ago NASA crowdsourced potential names to be used when the new Pluto pictures showed what the surface was like. They received about 40,000 submissions, which shows just how popular the thought of having your brilliant suggestion adopted as a celestial landmark must be.

In the category of “names for historical explorers”, the short list includes Hillary, our most famous climber, and Kupe, our most illustrious navigator. Of course, call a mountain range “Hillary” today and a large percentage of Americans will think it’s named for Hillary Clinton, and no doubt think there’s a conspiracy afoot. And speaking of conspiracies, yes, there has been some contrarian activity claiming that the photos, and indeed the entire mission, have been faked by NASA, which is in cahoots with aliens.

On a lighter note, some people have seen in the heart-shaped plain a similarity to the head and ears of Walt Disney’s famous dog.

On the subject of names, Charon, Pluto’s largest moon, is the name of the ferryman of the dead in Greek mythology. And that’s a logical choice, because Pluto, like Hades, is one of the mythological names for the underworld. But that’s not why Charon got that name—or at least only in part. According to moon’s discoverer, James Christy, he suggested the name Charon to honour his wife Charlene, who went by the nickname Char. Her reaction to having her (slightly modified) name immortalised in space was: “A lot of husbands promise their wives the moon, but mine delivered.”

Pluto and Charon display striking color and brightness contrast in this composite image from 11 July.

Pluto and Charon display striking color and brightness contrast in this composite image from 11 July. Photo: NASA

Charon is so large (relative to Pluto, which itself is less than twice the length of NZ in diameter) it forms a binary planet with Pluto, and that’s in fact how it was discovered: it was causing Pluto to wobble in its orbit. Think of the hammer throw athletics event—the weight of the hammer causes the thrower to move around in the throwing circle. Photos of Charon from the mission have shown it to be a beautiful orb reminiscent of our own moon. Nix, on the other hand—one of Pluto’s four other moons—looks like an orbiting potato.

One nice moment in the excitement of the Pluto flyby was that a daughter of Clyde Tombaugh, the discoverer, was invited to witness the first photographs as they came through at the NASA control centre. When she learned that the heart-shaped plain was to be named after her father, she said: “He loved astronomy, and what better way to say it than to have a heart named after you.”