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Climate Changes Could Affect Pacific Fisheries

Ocean acidification, stratification, hypoxia zones could affect seafood industry


European regulators believe commercial fisheries worldwide could lose as much as $17 billion to $41 billion in landings by 2050 due to the broadening effects of climate change.

In all geographic regions, a 2014 summary and assessment from the European Climate Foundation and Intergovernmental Panel on Climate Change (IPCC) said, the atmosphere and oceans are warming, the volume and extent of snow and ice are diminishing, sea levels are rising, and weather patterns are changing. Researchers claim that the ocean’s rapidly changing chemistry and physical conditions are already taking a toll on commercial fisheries by altering the distribution and abundance of marine species and ecosystems.

Temperature and oxygen level changes directly impact fish and shellfish, changing their migration, spawning and feeding patterns, as well as their abundance and distribution. Alterations in temperature, oxygen levels and food availability would also likely alter distribution and abundance of top predator species, such as albacore tuna. Distribution changes affect the composition of catches, leading to by-catch of non-targeted species and other problems, such as political conflicts over fishing in certain regions as species migrate to more favorable conditions.

A 2014 Pacific Northwest study used global climate models to project how the distribution of 28 near-surface fish species could shift by 2050.

“As the climate warms, the species will follow the conditions they’re adapted to,” said Richard Brodeur, a senior scientist at the NOAA Northwest Fisheries Science Center research station in Newport, Oregon.

Anticipated effects could push West Coast commercial fishery species, such as salmon, northward by an average of 30 kilometers per decade, shifting fishing grounds and significantly altering the economic and cultural foundations of fishing communities. Some species would likely move into northern habitats, especially the Gulf of Alaska and bering sea, and some species would simultaneously disappear from areas at the southern end of their distribution ranges, especially off the Oregon and California coasts. Diversity in northern fish communities, now typically dominated by a few very prolific species, could increase as southern species enter the region, leading to new food web and species interactions, and significant changes in marine communities and ecosystems.

Fisheries along the Oregon, California, and Washington coasts are already experiencing some of the effects of climate change, most notably rising ocean acidification, upwelling, and length and intensity of hypoxia (low oxygen) zones. Some species shifts are already occurring, as predatory Humboldt squid from Central and South America have invaded West Coast waters during the past few years, albacore tuna have moved northward, and eulachon (smelt) have disappeared at the southern edge of their range.

Downside of Upwelling

Upwelling systems cover less than two percent of the ocean surface, yet researchers say they contribute 7 percent to primary global marine production, and 20 percent of global fish catches.

In 2014, researchers from OSU and Northeastern University noted that climate change could boost the frequency of upwelling in several ocean current systems around the world, especially those at higher latitudes, creating changes in marine biodiversity and affecting some of the world’s most vital fisheries. Researchers say coastal upwelling has intensified during the past 60 years, and climate change is producing a general boost in upwelling due to strengthening winds caused by the changing differentials between land and ocean heating. Upwelling plays a vital role along the coasts of Oregon, California and Washington, and hypoxia (low or no oxygen) zones have persistently appeared in Pacific Northwest waters during the past decade.

Because upwelling of colder, nutrient-rich water boosts marine productivity, an increase in upwelling could enhance some fisheries. But ocean surface warming could also increase “stratification” – the horizontal layering of ocean water of different temperatures, creating and maintaining a warm, near-surface layer and a deep, cold layer. If extensive, researchers say stratification could boost the frequency and severity of hypoxia or low-oxygen zones, separating upwelling from the deeper nutrient-rich cold water, and pose “a significant threat to the global function of fisheries and marine ecosystems.” Depending on where the layers of warm and cold water settle in, along with local undersea terrain and currents, hypoxia could become either less common or more severe.

Upwelling also plays a role in the effects of ocean acidification on shellfish and other fisheries. Researchers say that the Oregon and Washington coasts and estuaries feature “a potent combination” of risk factors: cold waters, upwelling currents that bring acidic water closer to the ocean’s surface, acidic rivers, and nutrient pollution from land runoff.

A 2014 vulnerability study noted that ocean acidification has so far cost the oyster industry in the Pacific Northwest more than $110 million and jeopardized about 3,200 jobs. Fortunately, a robust effort led by OSU researchers to help oyster hatcheries recover from near-catastrophic larva die-offs during the past 10 years, but researchers claim the cumulative effects of on-going climate change could eventually overwhelm such mitigation efforts.

Adapt or Perish

The Pacific Northwest coast is among five areas the Sustainable Fisheries Partnership (, a not-for-profit organization founded in the United States in 2006, has designated as places to watch closely as climate change continues to wreak havoc on the ocean environment.

Not all fish can adapt, and some species could potentially die out. As go fish, so go fishermen.

“If it gets warmer, the fish they depend on are going to move up north and that means more travel time and more fuel will be needed to follow them, or else they may need to switch to different target species,” Richard Brodeur noted. “It may not happen right away, but we are likely to see that kind of a trend.”

Scientists say collaboration among natural, social, and economic researchers, fishery managers and commercial fishermen can help fend off the impacts and adapt to the effects of climate change on commercial fisheries and communities that depend on the sea. Researchers say adaptations include using selective fishing gear, an evolving process, to avoid particularly vulnerable and endangered species, moving to new fishing grounds based on projected climatic shifts rather than “the current ad hoc basis,” and – as unpalatable as the idea is to commercial fishermen – accelerated expansion of aquaculture “to compensate on a national, regional or global basis for the anticipated fall in wild-caught fish and shellfish.”

Unfortunately, while adaptation is possible, methods are limited, and the estimated worldwide cost for the fishing industry to do so between now and 2050 is $30 billion per year.

Improved policies and management and better monitoring systems, relocating fishing effort, and reducing non-climate change-related stressors can help reduce impacts. Other options include vulnerability assessments of fisheries, strengthening coastal zone management “to reduce land-sourced pollution, overharvesting, and physical damage to resources,” and creating new habitats such as artificial reefs to act as fish nurseries.

Some choices for adaptation – such as more flexibility in international fisheries management agreements and revising marine protected areas in response to climate-induced ecosystem shifts and habitat changes – bristle with potential conflict.

As resilient as the commercial fishing community can be, researchers agree that adaptation and mitigation would eventually reach a saturation point and “become progressively more difficult” (impossible in some situations) as climate change progresses and accelerates. Yet fishermen – accustomed as they are to responding to nature’s whims and tantrums, as well as those of politicians, fishery managers, and others - say they will persist, adapting as much as needed to maintain their livelihoods and a way of life for as long as possible.


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