August 23, 2013 — “As fish stocks migrate and as fish move north into colder water,” says Mike Conathan, who’s director of ocean policy at the Center for American Progress, “they're moving into areas where the industry is not necessarily set up with the proper gear to catch the species that are moving into their waters, and they also may not have permits to catch those fish.”
The changing environment isn’t even part of the computer models used to simulate fish populations and set catch limits.
Dr. Steve Cadrin of UMass Dartmouth’s School of Marine Science and Technology says there’s a reason for that. Modeling the full complexity of marine ecosystems is incredibly difficult. So fishery scientists focused on the factor that had the most influence over fish numbers – fishing. But as regulations have reigned in over fishing and the size of the fishing fleet has shrunk, environmental factors have become more prevalent.
For decades, fishery management has focused almost exclusively on the need to restrict fishing. Now, environmental changes are forcing fishermen and regulators to reevaluate their traditional practices.
Ernie Eldredge has been fishing all his life – clamming, long-lining cod, and crewing on sea scallop boats. But weir fishing is his love and mainstay. Last May, Eldredge pulled up something (or rather, two somethings) in his Chatham nets that even he’d rarely seen before – an Atlantic croaker and a grey triggerfish.
Weir fishing on Cape Cod is a tradition that dates back hundreds, if not thousands, of years. The circular nets anchored by hickory poles are like underwater corrals that trap fish as they migrate along the coast. Eldredge still uses some of the gear his father did, and others before him. The chain stretches all the way back to the Native American inhabitants of Cape Cod.
Looking out over one of his weirs, Eldredge says he’s witnessed a major shift in recent years. The odd southern fish is part of it. The bigger problem, though, is that Eldredge’s traditional targets have moved offshore out of reach of his nets. This weir is empty, and he’s already disassembling his others two months earlier than usual. He blames climate change.
Rising carbon dioxide levels have profound consequences for ocean ecosystems. Water temperatures increase, ocean chemistry changes, and weather patterns shift. The microscopic plants and animals at the base of the food chain respond and the impacts reverberate through the ecosystem. The location, growth, reproduction, even behavior of fish is affected.
Coping with climate change will take an equally Herculean shift in fishery science and management. Many experts say the key to weathering climate change is something called ecosystem-based management. As the name implies, the idea is to base any one decision on a comprehensive understanding of the entire ecosystem. It’s a logical idea but far from simple.
The first step is getting a handle on the physical and chemical changes taking place in the ocean. Dr. Jon Hare and his colleagues at the Northeast Fisheries Science Center have documented deviations in temperature, salinity, acidity, and nutrient levels in New England’s waters. They’re also seeing shifts in wind patterns and ocean currents in the Gulf of Maine. And that translates into ecological changes.
Read the full story and listen to the audio at WGBH