From the Town Landing: Voting with their fins

This column originally appeared in the February issue of National Fisherman magazine.

Now that the dust has settled a bit from the intense political debate that swirled through the Copenhagen climate change conference, we can all take a step back and ask ourselves what current research shows we might expect for Gulf of Maine fisheries in the future.

In the lead-up and immediate aftermath of Copenhagen there was a great deal of media coverage about the stolen e-mails from a British climate change research institution, which skeptics believe is the smoking gun of a vast scientific conspiracy behind the global warming hoax.

Nevertheless, the overwhelming majority of data from vast number of scientists across the globe continues to demonstrate the reality of and the broad-scale threat that climate change presents. And we use the term "climate change" deliberately, rather than "global warming," to underscore the point that the effects of greenhouses gases in the atmosphere and in the oceans will affect different areas differently.

One of the most persistent misconceptions in the climate debate is that just because not all areas have or will warm up does not mean climate change is a hoax.

Many researchers, including those in New England, are trying to figure out how to deal with the climate change problem. Meanwhile, of course, fish are not waiting on policymakers to make their move; they are voting with their fins. Recent reports show that the ranges for several species of fish are shifting as the organisms are pushed from their usual haunts to waters with temperatures to which they are adapted.

The Northeast Fisheries Science Center released its "Ecosystem Status Report for the Northeast U.S. Continental Shelf Large Marine Ecosystem" in 2009. The report identifies atmospheric warming as a significant driver of ecological change in the shelf waters of the Northwest Atlantic.

Warmer air affects ocean temperature, winds, river flow, and currents, setting off a series of effects that make fish and other marine creatures take notice. Because temperature affects a fish's metabolism, growth, consumption and maturity, the authors of the report note that "temperature is one of the most important governing environmental factors for marine organisms." Each species has a maximum and minimum temperature that it can endure and a narrower range of preferred temperatures.

Water temperatures have changed since 1982; much of the Northeast shelf, running from the Gulf of Maine to North Carolina, is warmer, but some is colder. As a result, much less of the shelf experiences moderate temperatures.

Analysis of 40 years' worth of trawl survey data revealed that the balance between species that prefer warmer waters and those that prefer cooler has flipped: warmer-water species now dominate their cooler-water cousins, and the geographic line between the ecologically distinct fauna of the northern and southern shelf areas is moving northward. Red hake is a good example.

Once abundant in the shelf waters of the Mid-Atlantic Bight, this species is now found primarily in the western Gulf of Maine.

A companion study, published in Marine Ecology Progress Series, presents the results of an analysis of trawl survey data for 36 species, including several flounders, hakes, skates, cod, haddock, pollock, herring, mackerel, redfish, alewives, and shad. The study detected significant changes in the distribution of 24 of the 36 species studied.

These species are shifting their habitats either to the north or to deeper waters. What hasn't changed was the water temperature in which the species were found: These fish are shifting to find temperatures that match their habitat preferences. The changes in distribution don't reflect annual fluctuations in temperature but correlate instead with large-scale climate change.

Southern species are expanding their range. In the Gulf of Maine, the options for finding new territory with familiar temperatures are limited. Some species, such as white hake, American plaice and wolffish occupy a more limited geographic range area than before temperatures changed.

Some, like cod and halibut, have shifted into deeper water. Still others, including pollock and cusk, have done both. But the bottom line for all of these species is that there's a limit to where they can go to escape warming waters.

The authors of the study suggest that species with nowhere to go may experience changes in growth, reproduction and recruitment and that climate change may play a role in the failure of some stocks to rebuild.

As the effects of climate change ripple through marine ecosystems, the implications for fisheries management are daunting. The current approach to management is already unwieldy; it is slow to respond to changing conditions and new information and is based on models that do not reflect the underlying complexity of marine ecosystems. The prospect of more of the same for managing fishery resources that are responding to rapid changes in the marine environment is not a happy one.

What changes can fishermen make to adapt to the changing distribution of fish stocks? Maybe they can follow the fish they are used to harvesting. Or, more practically, learn to target the fish now available to them.

To a certain extent, successful fishermen have always adapted to the unpredictable nature of changing fish distributions on an annual basis, but it is troubling indeed to think that we may be well on our way to making fishing even less predictable and more expensive at best, or at worst making the gulf uninhabitable for many of the species that have supported our fisheries for decades-if not centuries.

Anne Hayden is an independent marine policy analyst based in Maine. Philip Conkling is publisher of Working Waterfront and President of the Island Institute.