Fisheries and Climate Change

Family and small-scale fisheries, as well as the fishing communities that depend on them, will be dramatically affected by climate-induced changes in the fishery ecosystem.

By Boyce Thorne Miller, marine ecologist and Science Coordinator at the Northwest Atlantic Marine Alliance (NAMA), with the assistance of Ariele Baker, former intern at NAMA. Miller has authored/co-authored four books on marine biodiversity and has worked with many national and international environmental organizations.

Photo credit: USFWS/Jerry Reid, Flickr

The word “fisheries” refers to multiple parts of the fishing industry, including the habitats where fish are caught or farmed, species or types of fish, and the commercial acts of catching, processing, and selling fish. We are already seeingsignificant biological impacts, but some of the long-term impacts are still unknown. When climate change is combined with other stresses like overfishing, large-scale industrial fishing methods and pollution, the results could be disastrous for millions of people. Increased food insecurity, poverty and environmental degradation lie in wait if we don’t regulate our fisheries globally and protect small-scale fishers.

Symptoms of global climate change include rising atmosphere and ocean temperatures, increased frequency and intensity of storms, changing ocean current patterns, and sea level rise. In addition, the cause of climate change -– increasing carbon dioxide in the atmosphere — also causes ocean acidification when excess carbon dioxide dissolves into the water. These changes create physical, chemical and biological instabilities in ecosystems that affect the health, abundance, and variety of fish stocks and species. One example of how these changes affect fisheries is through the way water temperature alters reproduction and survival of species, changing which fish live in which areas. Sensitive juvenile life stages are subject to climate-induced changes affecting their chance of living to adulthood. And ocean acidification is particularly threatening to shellfish and corals dependent upon the ability to build calcium carbonate shells and structures.

Two examples of large, important fisheries in the United States that are vulnerable to climate change and ocean acidification are the Gulf of Maine — and the adjacent waters in New England – and the Gulf of Mexico. Both of these ecosystems are places where major ocean currents mix. New England is a transition zone between the cold waters of the north and warmer waters from the south, while the Gulf of Mexico receives water from the Mississippi River and the Caribbean that mix and form a nutrient-rich ecosystem. In New England some cold-water species are living near the highest temperatures they can tolerate, while many warm-water species are near the low end of their temperature range. It is easy to see that warming waters could drastically alter the mix of species and fisheries in these sensitive and critical areas.

Regulations have to be mindful of and keep pace with changes in climate, not to mention working to minimize climate change as much as possible.

Seafood consumers will also need to change their species preferences in local markets. This is because overfishing of certain species of fish or shellfish makes them much more vulnerable to climate change and ocean acidification. For instance, there could be changes in abundance and species mix among groundfish (fish living on the bottom and generally fished together) in New England. That mix currently includes market favorites like cod, haddock, flounder and halibut.

Atlantic Bluefin Tuna , the object of another popular and lucrative fishery, is a highly migratory fish that is dispersed across the entire Atlantic and spans the oceans between the Gulf of Maine and the Gulf of Mexico where tuna spawn. These baby tuna cannot tolerate water temperatures above 80 degrees. Changes in sea surface water temperature due to climate change may kill them before they leave the Gulf of Mexico. Simultaneously, some of these Bluefin tuna from the Gulf of Mexico find feeding grounds in Canadian and New England waters, including the Gulf of Maine, where their common prey may be altered. For species like this, the impacts of climate change and oceanic warming may be very different at different stages of their life cycles. As global sea surface temperatures increase, these and other species of fish will be affected.

Mismanagement of fisheries allowing overfishing will compound the problem. Industrial-scale fisheries are particularly prone to creating such problems before management can catch up and correct them. Small-scale fisheries that are properly monitored can often respond more rapidly.

Obviously, fishing communities will be dramatically affected by climate-induced changes in the fishery ecosystem and the ability and willingness of fishery management and markets to respond to these changes. If efforts lag, depletions may become severe with economic and social impacts on fishermen, their families and the communities that depend upon their success.

The People’s Climate March drew 400,000 people to the streets of New York City on September 21, 2014. Photo by Beatriz Beckford.

Precautionary management programs for fisheries that are vulnerable to climate change must anticipate oceanic changes and adapt quickly. Creative responses to climate change and other future changes in ecosystems and fisheries are needed. When there are fewer fish spawning or juvenile stages are not surviving as well, there are less fish to be caught, but often management, fisheries policy and markets cannot keep pace with these changes unless the scientific research and monitoring are adequate and timely and the management and marketing strategies are nimble.

Additionally, non-fishing activities must take impacts on fishery ecosystems into account and be equally adaptive to climate change and its impacts to avoid compounding negative impacts on fish abundance, variety and reproductive success.

In order to protect oceans, maintain fisheries, and continue to feed coastal communities all over the world, policies that prevent overfishing, reduce emissions of greenhouse gases that are causing climate change, and reward and incentivize fishermen and fisheries to steward the oceans are vital.

Updated 12/2014