Fishing for Answers in the Deep Blue Sea

The IoT can help us better understand how industrial fishing impacts sharks and other important marine species. But sometimes the technology fails to reel in answers.
By Mary Catherine O'Connor
Mar 23, 2016

Last week, I took a break from my day-to-day duties at IOT Journal to travel to Palau, a small island nation in Micronesia. It sounds like a vacation, but (aside from a lovely day of snorkeling) I was actually working on a freelance project: reporting for The Guardian on a research project that The Nature Conservancy is running in partnership with fishing company Luen Thai. The project's goal is to evaluate whether some small changes in how Luen Thai's tuna fishing boats operate might reduce incidental bycatch of non-target fish. (Bycatch refers to the hooking—or netting, based on the fishing process used—of species that are not the fisher's intended catch.)

But within hours of arriving, I realized that IoT technology is being employed as part of the research project. I guess my work follows me everywhere, even to remote islands in the Pacific.

Bycatch is a significant problem in fisheries around the world, not only because the fish that are unintentionally caught sometimes die—which, in turn, hurts the marine ecosystem, especially when bycatch include keystone species with low reproductive rates—but also because bycatch takes time and resources away from catching the target fish.

Sharks are often victims of bycatch by long-line tuna boats. When one is hooked, the crew cuts the line and releases the animal back to the sea (unless they are unscrupulous, in which case they might cut off its dorsal fin and sell it on the black market for shark fin soup). But what happens to bycaught creatures that are released intact? Does the trauma of being tethered to a fishing line underwater for some untold number of hours and then quickly yanked to the surface cause irreparable harm, or do the released animals tend to survive?

Research biologists have, for many years, used technology to try to answer that question, using various types of RFID tags and other approaches to track post-release mortality. But the most effective tools are called pop-up satellite archival tags (PSATs). These devices are designed to remain on an animal for a set number of days, weeks or months before automatically self-releasing and floating (popping up) to the water's surface, where they transmit stored data to scientists via a satellite link.

For the Nature Conservancy's research project, shark expert Michael Musyl, principal scientist of the Pelagic Research Group, is using PSATs to track the post-release mortality of two species—blue sharks and silky sharks—that are bycaught by the Luen Thai fishing vessel being used in the experiment. (PSATs are also utilized in general research, not just specifically to track bycatch mortality.) The tags being used, manufactured by Wildlife Computers, contain sensors that collect data regarding depth, temperature and speed of movement. A tag is set to release after 30 days, but if the shark significantly slows down for an extended period, or descends to a depth well beyond its normal range (in this case, 1,700 feet or lower) and remains there, the tag releases before hitting the 30-day mark. In those cases, the shark is presumed to have died.

It's a pretty handy technology, Musyl told me, but one that is in need of improvement. In fact, he and his colleagues conducted an analysis of 731 PSATs, manufactured by either Wilderness Computers or Microwave Telemetry, deployed in various marine research projects all around the world. They published their findings in 2011.

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