Shark Fears Threaten Newly Identified Dolphin

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A newly described species of dolphin, the Australian humpback dolphin, was just named a few days ago, and it’s already under threat.

Human fear of sharks, which has let to shark nets being set around coastal areas, has caused the accidental capture of the newly identified dolphin.

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According to a paper published in the journal Marine Mammal Science, the dolphins wind up as by-catch “in shark nets set around beaches to protect bathers.” Fisheries also pose a threat, as do habitat loss and degradation from coastal development, pollution and climate change.

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The dolphin is so new that it hasn’t even been mentioned yet in most texts. John Delaney, spokesperson for the Wildlife Conservation Society, explained to Discovery News, “The newly named Australian humpback dolphin, Sousa sahulensis, is now one of four recognized species of humpback dolphin. The Australian humpback dolphin is gray in color and has a characteristic ‘cape’ pattern on its back.”

Delaney added that this new dolphin seems to live mostly between waters off of northern Australia and New Guinea. It doesn’t appear to mix much with the other three species of humpback dolphins. In fact, a “zoogeographical border known as the Wallace Line” seems to separate the Australian humpback dolphin population from the population of Indo-Pacific humpback dolphins.

All of the dolphins, however, are at risk of injury or death due to capture in the nets set out for sharks.

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The study, co-authored by Thomas Jefferson of Clymene Enterprises and Howard Rosenbaum of the Wildlife Conservation Society, mentions how the dolphins have been caught in nets set out at both South African and New South Wales beaches.

In many cases, the sharks themselves die, depleting their already low numbers. Sharks have relatively few young and go through lengthy reproduction cycles, so it takes a long time for them to recover population losses.

In other instances, the sharks are captured in the nets and then relocated away from humans. A study in the latest issue of the journal Animal Conservation, for example, reports that The Shark Monitoring Program of Recife, Brazil, reported 100 percent survival of endangered sharks and a 97 percent decrease in shark attacks when the sharks were caught and then relocated. It didn’t mention how any accidentally caught dolphins fared, however.

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At least the goal in Brazil’s program is to keep the animals alive while also protecting humans. The dolphins, which aren’t even a threat to people, often wind up as innocent victims, particularly when the objective is to kill rather than to relocate the sharks.

So far, there is no population estimate for the Australian humpback dolphin, but the authors warn that it is unlikely that more than a few thousand dolphins of the species exist, based on available sighting data.

It’s therefore a bittersweet victory to learn of a new species, only to find out that we are both intentionally and unintentionally killing it.

Photo: Australian humpback dolphin. Credit: R.L. Pitman