Two Undersea Robots are Saving Marine Life From Lost and Abandoned Fishing Nets

Now if only they could get rid of all the ocean's plastic next.

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Sep 15 2015, 3:00pm

Lowering a Remotely Operated Vehicle (ROV) into the water. Image: NOAA's National Ocean Service/Flickr/Flickr

Can underwater robots save fish from tangling in nets? That's the problem the Northwest Straits Commission, a nonprofit organization dedicated to preserving the ecosystem of Washington's Puget Sound, tried to solve by using two remotely operated underwater vehicles (ROVs) to pick up derelict fishing nets off the sound's seafloor, where they've already removed over 5,000 nets as of the end of last year.

Oceans and shorelines are very much unequipped to keep up with humans and their ample feed of garbage. Plastic bits, big and small, are big killers, and we've basically made seabirds into flying trashcans. But fishing gear, which is actually meant to be in the water, can unintentionally kill crustaceans, sea turtles, mammals and seabirds, too.

640,000 tons of derelict fishing gear is added yearly to the swirling trash pile, and includes fishing nets and crab pots that have been damaged, abandoned, or lost. If left in place, these nets not only endanger low-lying wildlife, seabirds, and other fishing vessels—they can cause damage that's 14 times more expensive than simply monitoring and removing derelict fishing gear in the first place.

Extraction is a bit of an operation, and typically, trained divers remove these nets by hand. It's dark on the floor of the sound and nets are liable to simply break up and get lost in the water if too abruptly pulled, so one ROV cuts up the nets into manageable pieces, while a helper ROV monitors the situation. The ROVs then attach a surface retrieval line to haul the pieces up one at a time, similar to what divers currently do.

A boat on the Puget Sound. Little does it know what lurks beneath. Jonathan Miske/Flickr/Flickr

However, there's also potential for ROVs to help with problems that divers currently can't address: deep water nets. Since the beginning of net-removal effort in 2002, the Washington Parks Department, in partnership with the Foundation, have been skittish on sending divers below 105 feet, citing safety concerns. But because the ROVs the Commission has been using are rated for much, much lower than the lowest point of the sound (905 feet), that might not be a concern for much longer.

A 2009 study published in the Marine Pollution Bulletin concluded that there are clear economic incentives for the fishing industry to get rid of the derelict fishing gear from the sound. As of 2013, it was estimated that the nearly 4,500 nets removed by the foundation were entangling 3.2 million animals each year. But without the necessary equipment to actually retrieve the nets on the sound floor, fishing vessels have no choice but to leave them at the bottom.

With the help of these underwater robots, however, Puget Sound might finally see some clearer, healthier and safer seafloor.