Endangered porpoise thrown lifeline as dolphins drown

By Tracy Brighten

The Mexican government makes a late bid to save the world’s smallest marine mammal, while New Zealand lets the world’s rarest dolphin drown 

Vaquita porpoise Natural History Magazine

The vaquita porpoise population has declined as a result of drownings when porpoises are unable to reach the surface to breathe after entanglement in gillnets used in shrimp fishing. More recently, the gillnet threat has increased with the illegal fishing of the endangered totoaba fish, whose swim bladder is a Chinese delicacy fetching up to $10,000 a kilogram, smuggled to China via California.

The Mexican government has just announced a two year ban on gillnets in 5,000 square miles of the upper Gulf of California. The government will pay out $72 million to cover compensation to fishermen for lost shrimp catch over the two years, during which time alternative sustainable fishing methods will be researched.

Alongside environmental and community groups, the navy will be involved in enforcing the ban using drones and satellites, as well as patrol boats. The ban is the result of co-operation between the World Wildlife Fund, fishing groups and the Mexican government to save the vaquita porpoise.

Like the vaquita, the Maui dolphin’s biggest threat is from invisible fine-mesh gillnets. Fishing-related activities have been found to cause 95.5% of human-related Maui mortalities.

Science Nutshell Single Maui dolphin by Will Rayment

Up to 1.6m long, the tiny Maui with distinct rounded dorsal fin is a subspecies of Hector’s dolphin. Not only is it the world’s smallest dolphin, but with numbers estimated at only 55 adults over one year old, it is also the world’s rarest. A female Maui does not reach reproductive maturity until 7 to 9 years old, giving birth to one calf every 2 to 4 years. With only 20 breeding females left, the loss of just one female is significant to species’ survival.

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.

Will the New Zealand government follow Mexico’s example then and throw a lifeline to its endangered endemic marine mammal? Unfortunately, New Zealand’s environmental record of late does not match its 100% Pure New Zealand tourism marketing brand.

While there is a government set net ban, environmental groups, including the International Whaling Commission, argue for the zone to be extended to all coastal regions around New Zealand where Maui and Hector’s dolphins are found, including harbours and offshore to the 100m depth contour.

Existing protection zones seem to favour fishing interests rather than dolphin distribution.

Unless governments can be persuaded that a healthy environment benefits a nation’s economy, gillnet fishing threatens to wipe out the vaquita porpoise, Maui dolphin, and other vulnerable marine and bird species. The price to pay for eating fish caught by non-environmentally friendly methods could be very high indeed.

Image credit: 1. Vaquita porpoise on Flickr/Natural History Magazine (Attribution-NonCommercial-ShareAlike  license) 2. Maui dolphin on WWF/ Will Rayment. 

First published on Science Nutshell March 20, 2015


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About Tracy Brighten

With her passion for nature, health and sustainability, Tracy writes creative content that connects with readers. She helps tell people's stories, build brands and grow businesses. Thrives on words, birds and enthusiasm. For hire at www.tracybrightenwriter.com.

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