sharks

Keeping Lights On For Turtles

August 8, 2019 By EarthWise Leave a Comment

Gillnets are one of the most common types of fishing gear and are used extensively in most places where people fish for food. They operate by suspending a wall of netting in the water column.

Unfortunately, they are not selective in the species they catch. Sea turtles are one of the most common bycatch species that become entangled in these nets. When turtles are caught in gillnets, they can drown and die. Marine mammals, seabirds, and sharks are also frequently caught in gillnets.

Recently, researchers have been experimenting with illuminating the nets with LED lights to see if increasing net visibility reduces sea turtle bycatch.

Studies in Mexico show green sea turtle bycatch is reduced between 40-60% with no changes in target catch. Studies in Peru show green sea turtle bycatch is reduced between 65-80% with no changes in target catch. Studies in Indonesia show green olive ridley, and hawksbill sea turtle bycatch is reduced by 60% with increases in target catch and catch value.

Recent research shows that net illumination also reduces bycatch of other protected species such as seabirds, sharks and rays, as well as dolphins and porpoises.

The use of illuminated gillnets could prove beneficial to both sea turtles and fisherman by reducing the bycatch that can damage fishing gear.

Studies are now underway off the coast of North Carolina, where state gillnet fisheries are carefully managed to reduce turtle bycatch. Initial studies show that net illumination does not change target catch rates and may even decrease the bycatch of unwanted fish species. When it comes to protecting sea turtles, it looks like a good idea to keep the lights on.

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Illuminated Nets Could Provide A Brighter Future For Sea Turtles

Photo, posted June 2, 2016, courtesy of NOAA via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Banning The Shark Fin Trade

July 4, 2019 By EarthWise Leave a Comment

Shark fins are considered a delicacy in many parts of the world, especially in China. Shark fin soup, for example, is often served at engagement parties and weddings. But the use of shark fins has come under increasing scrutiny in recent years, especially since an estimated one-third of fins are harvested from species deemed at risk.

Many of the fins used in shark fin soup come from a practice known as “finning,” which is an inhumane and wasteful practice where the fins are hacked from live sharks and then the sharks are thrown back into the water and left to die. According to U.N. estimates, 73 million sharks are killed every year for their fins.

The possession, sale, and distribution of shark fins is banned in 12 U.S. states, as well as in all European Union member states.

In 1994, Canada banned the practice of finning in its own waters, but allowed the import of fins to continue. Canada has been one of the largest markets for shark fins outside Asia, importing nearly 300,000 pounds of shark fins last year. But in late June, Canada passed a bill that bans both the import and export of shark fins harvested by shark finning. They are the first G7 and the first G20 country to do so.

But shark fins taken from sharks sustainably harvested for their meat will continue to be allowed in Canada. While demand for shark fins is decreasing globally, demand for shark meat is rising.

Since sharks still face a myriad of environmental pressures, including illegal fishing and high bycatch rates, there are concerns that this Canadian ban oversimplifies the threats facing global shark populations.

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Canada becomes the first G20 country to ban shark fin trade

Photo, posted January 4, 2013, courtesy of Andrew Currie via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Fish And Ships

April 25, 2019 By EarthWise Leave a Comment

Solutions to overfishing of certain tuna and shark populations have been hindered by some significant unknowns: where the fishing is happening, and where the fish are. But researchers from Stanford University have recently shed some light on this mystery.

According to a paper recently published in the journal Science Advances, the researchers have developed a map of shark, tuna, and ship movements that could help ocean managers identify regions of the sea where vulnerable species may be at risk.

The researchers’ work builds on a 2018 study in which four years of satellite vessel movement data was used to develop a machine learning algorithm that mapped the footprint of 70,000 different fishing vessels around the world. In their paper, the researchers zeroed in on the activities of 900 vessels from 12 countries in the northeast Pacific Ocean to figure out to what degree fishing fleets, sharks, and tunas overlapped.

The researchers combined the vessel data with the ocean habitat preferences of sharks and tunas obtained from a decade-long tracking program called Tagging of Pacific Predators (or TOPP). According to the IUCN, most of the 876 individuals tagged in TOPP belong to species that are either threatened or near-threatened.

By synthesizing this data, researchers were able to map where sharks and tunas would have the highest overlap with commercial fishing vessels. Increasing the transparency of where fish meets fleets will allow ocean managers to determine where international protections may be needed.

The United Nations is currently developing the world’s first legally binding treaty to protect international waters. The Stanford University researchers hope their findings can help with this treaty’s formulation.

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Tunas, sharks and ships at sea

Photo, posted June 20, 2011, courtesy of Mike Baird via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Fewer Snowbird Sharks

April 23, 2018 By EarthWise Leave a Comment

Blacktip sharks are snowbirds, to use a cross-species metaphor. At least, they usually are. The males of the species swim south to southern Florida during the coldest months of the year and head back north to North Carolina in the spring to mate with females.

Sharks In Hot Water

August 25, 2016 By WAMC WEB

The majestic great white shark has been around for a very long time. Its evolutionary origin dates back 14 to 16 million years. And while great whites still enjoy decent populations off the coasts of Canada, Australia, and the United States, the same can’t be said for South Africa’s great whites.

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