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Thursday, 19 October 2017

Atlantic cod - seeing is believing!


Atlantic cod, New England’s most iconic fish, has been reported at historic lows for years, but fishermen hope a new video monitoring technique will prove there are more of the fish than federal surveyors believe.

Ronnie Borjeson, who has been fishing for more than 40 years, says the federal surveys don’t match up with what fishermen are seeing. “I don’t care if you’re a gillnetter, a hook and line guy, a trawl guy,” he said, “there’s codfish everywhere up there. Everywhere. You can’t get away from them.”

Borjeson helped test a video rig designed by researchers at the University of Massachusetts Dartmouth that allows them to record fish underwater and count them on the video later. With this rig, scientists can sample a larger area in the same amount of time and hopefully improve federal estimates of how many cod are left.

For years, Atlantic cod has been reportedly overfished—but a new video monitoring technique may prove otherwise.

According to the National Marine Fisheries Service, cod are overfished, and in 2014, the spawning population reached its lowest numbers ever recorded. The once-booming cod fishery has been subject to increasingly strict regulations since the 1990s, forcing commercial fishermen to target less-profitable species while they wait for the cod population to recover.

Kevin Stokesbury, the researcher spearheading the project, hoped to create a more effective and transparent monitoring system by collaborating with local fishermen. “They know their gear and they know the distributions. So for me, I’ve certainly never discounted what they say,” he said. “You have to back that up scientifically, and I think that this is a means to do that.”

Federal scientists estimate the cod population by towing nets through randomly selected areas of the fishing grounds and hauling the fish on board to be counted. The results of these trawls are combined with information from fisheries observers and catch estimates to create a picture of the overall health of the fishery.

But cod are not evenly distributed across the ocean floor. The fish gather in tight groups to spawn, leaving large areas of habitat essentially devoid of cod and increasing the likelihood that a random sample will come up empty. The federally managed area in the Gulf of Maine alone is more than 30,000 square miles. With limited time and resources to accomplish their work, federal surveyors must rely on a small number of these surveys to accurately estimate the whole population.

And, according to Borjeson, “The general consensus [among fishermen] is they’re incapable of catching fish.”

Yet as Jon Hare, the Science and Research Director for NOAA’s Northeast Fisheries Science Center pointed out, fishermen “are targeting and looking for higher abundances of cod. That could also make their perspective on the abundance of cod different than what’s coming out of the [survey].”

Stokesbury thinks his video system can, at the very least, help scientists get a better idea of how many fish are in the spawning groups and help the fishery managers and fishermen see eye to eye.

The video rig has gone through several iterations to deliver clear images in the harsh, salty environment. The current version has two cameras and a set of LED lights facing backwards inside a fishing net. When fish are swept into the net, they pass the cameras and are funneled harmlessly out the open back end.

Hare agreed that the system holds promise, but cautioned that the work is not yet done. “You still need to extract [the information] from the video. You’re potentially looking at thousands of hours of video data,” he said.

Stokesbury and his team are working on this problem now. Currently the software takes two to three weeks to identify and count the fish for every week at sea. This is a vast improvement over the original method–graduate students counting by hand–but Stokesbury expects to reduce the processing time further as their software improves.

If that happens, Hare believes the system could be very useful. “As humans, we put a lot of faith in visual data,” he said, “Having the real-time visual information is a good approach to having people come to a common understanding.”

Borjeson hopes fisheries managers will incorporate video monitoring as soon as possible. “The system works,” he said. “People love it. They embrace it. It’s absolutely indisputably the way to do a stock assessment.”

Full story courtesy of NovaNet.
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