Tackling the Problem of Ghost Nets
Once they break free, they drift unrestrained, buoyed, submerged and battered by the wild waters and shifting ice sheets of Lake Superior. Yet they continue to entrap fish, waterfowl and marine debris, even though no fishermen will come to claim and clear them.
They’re called ghost nets, and they’re a problem in Lake Superior, where commercial and tribal fisheries depend on gill nets for their livelihood. In the Apostle Islands area alone, there are hundreds of commercial and tribal fish nets, spanning tens of miles. Sometimes, these nets come unmoored, creating hazards for wildlife and for recreational boaters and anglers.
To tackle the problem, Wisconsin Sea Grant has partnered with the Apostle Islands Sport Fisherman’s Association (AISA) and the Great Lakes Indian Fish and Wildlife Commission (GLIFWC) Law Enforcement Team. Using a two-year, $25,000 investment from the National Oceanic and Atmospheric Administration’s (NOAA) Marine Debris Program, the three groups will spend the next year organizing and holding a series of public workshops aimed at educating new commercial and tribal anglers on best net-management practices, as well as creating an educational video to detail the appropriate actions recreational boaters should take when they become entangled in a ghost net, or even a properly moored net.
Al House, a board member of AISA and member of Sea Grant’s advisory board, estimates that although only one percent or less of commercial or tribal nets break free and become ghost nets, they still need to be addressed.
“These nets are depleting a resource that’s finite,” House said of the Lake Superior fish population, rich in valuable species like trout, cisco and whitefish. “The idea is to move quickly to protect it.”
Currently, tribal fisheries have no requirement to report that their gill and trap nets have become unmoored. In some cases, several days may pass before a fisherman even notices that a net has broken free. Depending on what the ghost net encounters, it might float on the water’s surface or sink to the bottom, trapping debris and fish life.
“The challenge is definitely finding them,” said House. “They’re worse than the proverbial needle in the haystack. The idea is also to find an accurate assessment of the scope of the ghost net problem—nobody knows how many or how few there are.”
Eventually, the partners would like to develop and implement a GPS-based system for identifying, tracking and reporting ghost nets, as well as creating a second video on best-management practices fisheries can use to reduce gill net loss.
But the first step is education.
“This is really about raising awareness of how to be safe when you’re fishing,” said Titus Seilheimer, Sea Grant’s fisheries outreach specialist and the project’s principal investigator. “There’s lots of sources of entanglement risk out there, and you may not know what you’ve become entangled in.”
The safety video will include information for boaters on how to free themselves from any net, whether it is a ghost net or a properly moored one that a boater has blundered into.
The key is not to panic and to understand that the sooner you can extricate yourself, using the proper tools, the safer you will be and the less damage will be done.
House said the key to the project’s eventual success is that it’s designed as a partnership that involves the groups who most stand to benefit from raised awareness. That’s why GLFWIC’s support and involvement is so key.
“We’re not pointing fingers here,” House said. “We’re supportive of tribal and commercial fisheries, and their importance to the economy, and it’s certainly not their fault that nets break free. We can cooperate and make the whole situation better.”
Seilheimer agreed. “It’s a win-win for both sides,” he said. “Recreational anglers don’t want to get entangled. For the commercial side, not losing your gear is a good thing.”
Production on the first educational video is underway, and workshops are scheduled to begin early in 2015.
Dioxin Exposure — Dramatic Effect on Fish Sexual Development, Harm to Nose Tissues
Wisconsin Sea Grant-funded researcher Michael Carvan (right) and his research team fed both young rainbow trout and zebrafish food containing different levels of TCDD (tetrachlorodibenzo-p-dioxin) over a six-week period. Carvan, Shaw Associate Scientist at the University of Wisconsin-Milwaukee School of Freshwater Sciences, said their technique “more closely mimics actual environmental exposure to dioxin.”
They found that 28 days of exposure to high doses of TCDD (100 parts per billion) caused lesions in the zebrafishes’ noses, livers, kidneys, intestines and ovaries. The lesions in the fishes’ nose tissue are concerning because fish use their noses to navigate through water and to find streams for spawning. While testing whether the fishes’ sense of smell was impaired by dioxin exposure was not part of Carvan’s research, he’d like to follow up to see if lesions lead to behavioral problems and impeded spawning success.
Another surprising finding was that dioxin acted as an endocrine disrupter.
“It had a dramatic effect on the development of the female zebrafish reproductive tract,” said Carvan. “At higher dosage levels, we couldn’t identify any female zebrafish. They all looked male.”
Carvan said that rainbow trout are more sensitive to dioxin than zebrafish are. Because rainbow trout mature more slowly, researchers were not able to determine TCDD’s impact on that species’ reproductive tract, but Carvan suspects that their reproductive tracts would be affected by high levels of dioxin or dioxin-like chemicals.
Carvan said the amounts of dioxin they exposed the fish to were, “high for the average fish in Lake Michigan, but they’re not necessarily that high for a fish found in a polluted environment.”
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