Climate Change Forces Reevaluation of Fishery Management
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 netted something (or rather, two somethings) 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 just off the beach in Chatham, 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.
“Community composition of the phytoplankton the small microscopic plants in the sea, is changing,” says Hare. “Community composition – the zooplankton, the small animals, the little tiny crabs that eat the tiny little plants is changing. So we’re starting to sort of track these changes from the physics into the lower trophic levels the phytoplankton, the zooplankton, and trying to track it up to fish populations and marine mammal populations.”
Scientists now think that altered zooplankton populations may be one reason cod stocks haven’t rebounded as quickly as expected. In addition, water temperatures in southern New England are getting uncomfortably warm for cod. So they’re moving northward and offshore in search of cooler water. And they’re not alone. Over the past fifty years, more than half of all commercially exploited species have responded to warming waters by changing where they live. That includes the fish that used to fill Eldredge’s weir.
“In the height of the season it’d be nothing for us to fill up three boats and come home. Sometimes we’d fill three boats and go back and fill a couple more up,” Eldredge recalls with a wry laugh. “There were just so many fish out here. And that’s just gone now.”
While the impacts of climate change are increasingly apparent, that information currently doesn’t get factored into management decisions. The changing environment isn’t even part of the computer models used to simulate fish populations and set catch limits.
Dr. Steve Cadrin of U Mass 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 overfishing and the size of the fishing fleet has shrunk, environmental factors have become more prevalent.
The problem is, even if climate change were built into fishery assessments, no one is quite sure what to do about it. One possibility is blocking off areas of the ocean where fishing is prohibited so ecosystems can adapt to climate change.
“If we can protect those fish where they need to be to rebuild from fishing,” explains Peter Baker, Director of the Northeast Fisheries Program for Pew Environment Group, “they can have the resiliency to withstand other pressures like climate change.”
But federal regulators are actually considering reopening a number of historically closed areas in New England. Instead, they’ve opted for management schemes that set explicit catch allowances for each species. Ecosystem models could be used to match those limits to the fluctuations in fish populations resulting from climate change. But there’s more to this than just catch limits.
“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.”
Take Eldredge’s croaker, for example. Croaker is a near-shore species that’s regulated at the state level. In Maryland, that fish would have been subject to size limits and gear specifications. But here in Massachusetts, Eldredge says there are no regulations that he’s aware of. Historically, there’s been no need.
That’s just one example of the regulatory complexities that arise from climate change. In response, we may need a whole new paradigm for fishery management – one that favors flexibility and diversity over history and geography. Conathan says that’s going to be a major factor when legislators start in on the task of reauthorizing Magnuson-Stevens, the federal law that mandates and governs fishery management.
For his part, Eldredge says he counts himself lucky to be a weir fisherman. There are fewer regulations to contend with, and no long trips offshore. But weirs are the most fixed of fishing gear. They can’t just pick up and move to follow the fish. As he drives away from the weir, Eldredge says he’ll spend this winter mulling a difficult decision about whether or not to continue.
As croaker becomes more common in New England's waters, there's the question of whether it could replace the region’s iconic cod. Check out our comparison of the two species, including recipes, and tell us which one you'd rather eat.
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