UPDATE2: To see what is fishy about this story, see Bob Tisdale’s update here: http://wattsupwiththat.com/2013/05/16/washington-post-headline-worlds-fish-have-been-moving-to-cooler-waters-for-decades-study-finds/
From the University of British Columbia
‘Fish thermometer’ reveals long-standing, global impact of climate change
Climate change has been impacting global fisheries for the past four decades by driving species towards cooler, deeper waters, according to University of British Columbia scientists.
In a Nature study published this week, UBC researchers used temperature preferences of fish and other marine species as a sort of “thermometer” to assess effects of climate change on the world’s oceans between 1970 and 2006.
They found that global fisheries catches were increasingly dominated by warm-water species as a result of fish migrating towards the poles in response to rising ocean temperatures.
“One way for marine animals to respond to ocean warming is by moving to cooler regions,” says the study’s lead author William Cheung, an assistant professor at UBC’s Fisheries Centre. “As a result, places like New England on the northeast coast of the U.S. saw new species typically found in warmer waters, closer to the tropics.
“Meanwhile in the tropics, climate change meant fewer marine species and reduced catches, with serious implications for food security.”
“We’ve been talking about climate change as if it’s something that’s going to happen in the distant future – our study shows that it has been affecting our fisheries and oceans for decades,” says Daniel Pauly, principal investigator with UBC’s Sea Around Us Project and the study’s co-author. “These global changes have implications for everyone in every part of the planet.”
A summary of the study is available at http://www.pewenvironment.org/news-room/fact-sheets/warming-oceans-are-reshaping-fisheries-85899474034.
Me, I think it is just that the fish go where the food is, and cold water upwelling tends to make more food available. From NOAA:
The ecological effects of upwelling are quite diverse, but two impacts are especially noteworthy. First, upwelling brings up cold, nutrient-rich waters to the surface, which encourage seaweed growth and support blooms of phytoplankton. The phytoplankton blooms form the ultimate energy base for large animal populations higher in the food chain, including fish, marine mammals and seabirds.
UPDATE: Dr. Pat Mciahels writes in comments
Sent this to Leonard Bernstein, who got the story on the front page of today’s WaPo:
Hi Mr. Bernstein,
Congratulations in placing the fishery climate story on the front page! I have a couple of questions/observations that you may find interesting and worth commenting on.
The article cites a release by the Pew Foundation that clam populations that were comercially harvested in Virginia at the beginning of the paper’s study period (1970) are no longer viable and that fishery has moved to New England. If this is true, then the mean annual temperature of coastal Maine now should resemble that of tidewater Virginia in the early 1970s. In fact, data from the National Climatic Data Center show the average for the Tidewater Virginia Climatological Division were around 58degF in the early 1970s, while the Coastal Maine Division is averaging around 46 now. I am very surprised that Pew didn’t do such a simple fact-check test of hypothesis, or perhaps thought that no one else would look?
Further, with regard to commercial species that are fished in the deep ocean, the oft cited data of Sid Levitus and NOAA shows the expected massive dilution of surface warming at increasing depth. The change below 700 meters is a few hundreths of a degree (global average) while from 100 to 700 meters are a mere 0.1degC since 1955. This is where most commercial species live. I doubt that such a change is at all responsible for such substantial migration.
In fact, the attribution of fishery migration to climate change is very difficult. In a famous 2007 paper on distributional shifts and climate change in the Bering Sea, F.J. Mueter and M.A. Litzow wrote:
“A nonlinear, accelerating time trend in northward displacement (Fig. 5D), unrelated to temperature or any other climate parameter we tested (at any lag), suggests that mechanisms besides climate must be contributing to distribution shifts in the Bering Sea…The failure of our exploratory attempts to explain variability among species underlines the difficulties of this research problem.” [emphasis added]
I don’t see any of these issues addressed in Pew’s press release, and it seems to me that what they have provided is sorely lacking. I also have looked extensively at Cheung’s paper and I am once again amazed at what is getting through peer-review at Nature on climate change. They don’t measure any temperatures, they use a derived variable from species distribution data, and the temperature changes they derive are much much greater than those actually being measured in the regions in question. The reviewers should have at least asked for ground-truth temperature data.
Thanks for reading. Any comments?