The Fishy Side of Climate Change
Today, the U.S. Global Change Research Program released its Third National Climate Assessment. The Assessment is the result of more than 250 researchers, industry representatives, and government officials collaborating to examine the effects of climate change on our country. It’s an impressive effort, involving contributions from most of the U.S. cabinet departments, and analyzing both current and future impacts from climate change.
What does this report have to do with fish? A lot, it turns out. The National Climate Assessment starts out talking about familiar aspects of climate change—weather patterns shifting, stronger storms and floods, rising sea levels, and so forth—but then in Chapter 24, it turns specifically to the implications of climate change for U.S. oceans. In that chapter, the authors point out a number of troubling trends:
- The ocean is are getting warmer, and circulation patterns are changing in unpredictable ways.
- Ocean waters are becoming more acidic, as they absorb carbon dioxide from the atmosphere.
- Habitat loss will be seen in many areas, including Arctic and coral reef ecosystems, while other types of habitat may expand.
- Warmer waters tend to facilitate the spread of disease in marine life, potentially affecting corals, shellfish, finfish, and marine mammals.
Overall, climate change “will alter marine ecosystems in dramatic yet uncertain ways.” 
For those of us in the fisheries world, this is not news. We’re already seeing range shifts in fish species, as temperatures and circulation patterns change, and altered physical conditions may be the culprit for poor fish recruitment in several situations. In some places, like the Gulf of Maine, the entire ecosystem seems to be affected by climate change.
In the future these effects are likely to only get worse. And when you throw in ocean acidification—which impacts the shell-forming microorganisms down at the base of the food chain—there’s potential for things to go really haywire in our oceans.
These trends are extremely troubling, and they operate almost entirely outside the parameters of traditional fisheries management. Why? The models we use to manage our fish stocks assume conditions in the future will be pretty much the same as conditions in the past. Yet all the trends of climate change—shifting temperature and circulation patterns, altered habitat distribution, and varying primary productivity—involve conditions in the future being different from conditions in the past. So the models that we use to assess the numbers of fish in the ocean, determine the healthiness of the stock, and calculate harvest levels simply aren't able to factor in climate change.
Because we’re managing our fisheries with models that don’t account for climate change, it’s really important to build a firewall into our management strategy. This means catching fewer fish than we otherwise would and rebuilding depleted fish stocks quickly, in order to maintain our ocean ecosystems in a healthy state. The point is to back off with our pressure on the oceans—more than seems necessary, given today’s conditions—because we know in the future things are likely to change, and robust, well-functioning ecosystems can withstand change better than depleted or weakened ones.