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Acoustic Survey For Whales And Dolphins in Tanzania Detects High Levels of Blast Fishing Threatening Marine Life
New York (November 25, 2015) – WCS scientists conducting a large-scale survey of whales and dolphins along the Tanzanian coast have unintentionally revealed the extent of a major marine threat: blast fishing, a highly destructive fishing method using explosives to catch fish.
Conservationists listening for whales and dolphins off the coast of Tanzania during a month-long survey heard something unexpected in their hydrophones: the alarming explosions of fishermen using dynamite instead of fishing lines and nets to catch their quarry.
The research took place between March and April of 2015, when a team led by Dr. Gill Braulik of the WCS Tanzania Program spent more than 230 hours conducting an evaluation of marine mammals along more than 2,600 kilometers of transects in Tanzania’s coastal waters. In addition to surveying using visual observers with binoculars, the team also used hydrophones (underwater microphones) in an attempt to detect the presence of whales and dolphins below the surface of the ocean. The most frequently heard sounds were not marine mammals, but explosions.
“We heard blast fishing explosions far more often than the vocalizations of dolphin and whale species, which was unexpected,” said Braulik. “Not only is this type of fishing harmful to acoustically sensitive species such as marine mammals, it indiscriminately kills fish and other marine life, and can seriously damage coral reefs.”
The scientists collected acoustic data over a period of 36 days. During that time, they recorded 318 blasts up and down the length of the coast of Tanzania. The area of highest intensity for explosions was located near Dar es Salaam, the country’s largest city. Nearly 62 percent of all the detected blast fishing occurred within 80 kilometers of the city.
Further, the research team recorded between 50 and 70 blasts per day, and up to10 blasts/hour near Dar es Salaam, which was up to 10 times the frequency of other regions where blast fishing was detected. Some 70 percent of the blasts were recorded during the late morning hours, specifically between 9 a.m. and 1 p.m.
Fishers who practice blast fishing usually construct home-made bombs with bottles, fertilizer, kerosene, and occasionally use explosives sourced from the mining sector. Such a device can cause extensive damage to corals; an explosion near the bottom can demolish reefs over a radius of 1-2 meters. The explosions kill not only large fish (specifically by rupturing the animals’ swim bladders), but also juveniles, plankton and other invertebrates.
“As others have shown, blast fishing is a huge problem in Tanzania, but we didn’t expect it to be quite so bad and so ubiquitous” said Dr. Tim Davenport, Director of WCS’s Tanzania Program. “Fishing with explosives has the potential to destroy a critical source of sustenance for coastal communities. We hope these findings can have a real impact through law enforcement in the hotspots where the most blast fishing is occurring.”
Support for this work was provided by the Wildlife Conservation Society and the Pew Fellows Program in Marine Conservation at The Pew Charitable Trusts.
WCS (Wildlife Conservation Society)
MISSION: WCS saves wildlife and wild places worldwide through science, conservation action, education, and inspiring people to value nature. To achieve our mission, WCS, based at the Bronx Zoo, harnesses the power of its Global Conservation Program in more than 60 nations and in all the world’s oceans and its five wildlife parks in New York City, visited by 4 million people annually. WCS combines its expertise in the field, zoos, and aquarium to achieve its conservation mission. Visit: newsroom.wcs.org Follow: @WCSNewsroom. For more information: 347-840-1242.