Can looking to the future help preserve a historical fishery against climate change?

Editor’s note: This is the third in a multi-part blog series, Fisheries for the Future, examining the impacts from climate change on global fisheries and the opportunities to address these emerging challenges. Throughout the series, we’ll be investigating how climate change will impact the world’s supply and distribution of fish and what we can do to ensure the most sustainable future for ourselves and our planet. Learn more about this work: Resilient Seas

In New England, as in many other parts of the world that rely on fishing for food and income, there is a growing need to predict and adapt to climate change as it worsens. One of the most important aspects of dealing with climate change is to look ahead and put in place goals, objectives, scientific research and management practices that are responsive to future conditions. As we anticipate a climate-altered future, we will continue to value healthy ecosystems and the benefits derived from fisheries. However, healthy ecosystems and sustainable fisheries of the future may be very different from what we are used to. The ability of the oceans to support thriving ecosystems and fishing communities will depend heavily on actions we take today.

The New England Groundfish Fishery

New England’s storied groundfish fishery, which targets cod, haddock, a variety of flatfishes and other bottom-dwelling predators, is among the oldest fisheries in the United States. It was once said that a fisherman could walk across the waters of New England on the backs of the formerly plentiful cod, which fueled the regional economy following European settlement. The fishery also created a rich maritime heritage that continues to this day. That fishing heritage first belonged to the Native American peoples who long pre-dated colonization. Today, preserving this iconic fishery and the economy and culture it has built will require looking forward to an ocean evolving under a changing climate.

Fish on the move

The Gulf of Maine and Georges Bank, the complex basin and shallow underwater plateau that together have been the foundation of our regional fisheries, sit at the far southwestern edge of the range of many Northern Atlantic species. Historically, these have been coldwater ecosystems, albeit at latitudes that are typically much warmer elsewhere, due to the Labrador Current delivering frigid polar waters southward from the Arctic. However, this corner of the Northwest Atlantic now finds itself warming faster than almost any other ocean area on Earth. These warming waters are causing rapid shifts in the distribution of many species, generally to the north and offshore, seeking their preferred water temperatures.

Thus, species we normally associate with the Mid-Atlantic region — black sea bass, summer flounder, striped bass and others — are expected to continue to move north and become more abundant in New England as colder water species push northward. Fishermen in New England will see a shifting mix of species nearest their docks as warming progresses. Governance patterns must also change to manage for the shifting portfolios of stocks that no longer represent historical management decisions.

Climate change is making Atlantic cod recovery difficult, but this geographical shift might actually have some benefits for the future of the species. For many years, cod have become concentrated in a small pocket in the western Gulf of Maine bounded by Cape Ann and Cape Cod. Elsewhere, overfishing has caused near-complete localized extinction. Although warming waters are already decreasing the productivity of cod, spreading the stock more widely across the Gulf of Maine could increase resilience relative to today’s much more restricted distribution by hedging bets against localized declines. Important efforts to restore coastal prey fishes that cod feed on, especially sea-run herring, are helping to give cod a chance where they have been lost.

Forward-looking habitat management — anticipating changes in fish populations

If cod return to those areas, they will need time to re-establish. That process will be more complicated in a changing ecosystem, for the nature of seafloor habitats, water temperatures, surrounding fish and invertebrate species and other ecosystem attributes will be different from what cod once knew. It was therefore with laudable foresight that the New England Fishery Management Council and National Marine Fisheries Service together created a fishery closed area along the coast of Maine offshore from Penobscot Bay. That refuge is helping protect important habitats and can enable fledgling spawning groups to grow and possibly serve as a source of replenishment to areas elsewhere in the Gulf of Maine.

Climate change is the source of much uncertainty — examining life histories of popular fish

Of the 20 stocks included in the groundfish fishery, most live primarily away from shore, with some inhabiting the deepest trenches of the Gulf of Maine. But one unique species, the winter or blackback flounder, historically moved inshore to spawning and nursery grounds in estuaries and even salt ponds in the wintertime. Key habitats in those areas, including salt marshes, eelgrass beds and oyster reefs, are especially susceptible to effects of climate change as sea levels rise, waters warm and storms intensify. These habitat changes, among other impacts, mean that winter flounder are expected to suffer especially strong declines in productivity due to climate change.

However, some winter flounder are known to spawn in offshore areas as well. This means the stock as a whole might have the ability to counteract reduced inshore spawning success, to some degree, by capitalizing on deeper and increasingly colder waters. The effect of this life history diversity on productivity is but one of many scientific uncertainties we must confront in managing the stock, among other uncertainties related to climate change and incomplete accounting of just how many fish are being caught. Untangling these uncertainties and applying our findings to forward-looking management strategies will not be easy, but there are steps we can take in anticipation of changes that will come.

Climate uncertainty and responsive fishing rates — aligning good policy to biology of stocks

One of the central elements of any fishery management strategy is a harvest control rule, or HCR, which typically determines how many fish can be caught based on how many fish there are in the water. An HCR is arguably where science most directly confronts policy in fisheries management, as it reveals a great deal about the objectives of the fishery, policy requirements, scientific understanding and uncertainties and risk tolerance. In many fisheries, the HCR is simply to fish at a fixed but precautionary rate of fishing mortality that strikes a balance between achieving high yields when the stock is large, but not overfishing when the stock is smaller. Such a “fixed-F” approach can be effective when productivity fluctuates around an average level, as is the norm in any ecological system, but does not change in a consistent direction.

But species that are expected to decrease or increase consistently, like winter flounder, break this rule, which means a different approach is needed. When facing climate-driven declines in productivity that are exacerbated by scientific uncertainty, the HCR must be more responsive. Even if we do not understand all of the biological changes taking place, fishing mortality should decrease in real time as we detect declines in the stock and can then rise again with evidence of recovery. Such an approach is not yet used in the New England groundfish fishery, but could be adopted much more readily than other more complex management reforms. Indeed, neighboring fisheries in the Mid-Atlantic region have implemented this very approach.

New England can have abundant fisheries

For those of us who call New England home, the groundfish fishery has sculpted our waterfronts, history, folklore and cuisine. It can remain an indelible part of our region, as long as we look to the future while we embrace the past. The ecosystem will function differently as climate change continues to unfold and we must anticipate and prepare for that future. Strategic use of protected areas and responsive harvest policies, alongside other actions like recovery of prey fish and improved monitoring to track changes and impacts, can help us keep pace with a changing ocean. Although climate effects on New England’s ocean are especially strong, we know that these impacts are occurring around the world. In next week’s blog, we’ll delve into building and strengthening international institutions to allow for collaboration between countries as the fish they rely on change in abundance and distribution.

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