Many commercial fish stocks will likely shift their distributions dramatically as species respond to changes in ocean climate over the next 4 decades, according to a global analysis to be presented here tomorrow. The changing ranges could mean major disruptions to fisheries, with some nations seeing major boosts in yields and other countries--predominantly in the tropics--being the losers. Dozens of species that are unable to adapt will likely go extinct.
The findings come from a computer model created by William Cheung, now with the University of East Anglia in the United Kingdom, and colleagues at several institutions. The team looked at the present ranges and environmental requirements of 836 commercially caught species of fish, such as cod, and 230 invertebrate species. Then they checked how conditions such as temperature and altered currents would alter the habitats under three scenarios of greenhouse gas emissions.
In all the scenarios, most species migrate toward the poles. With the highest emissions, species will adjust their ranges on average 79 kilometers per decade. In the scenario of lowest emissions, the rate would be 44 km per decade. This would mean dozens of extinctions for species that are unable to migrate, in particular those in polar regions, as the team reported at a meeting last year (ScienceNOW, 10 July 2008). The findings will be published tomorrow in Fish and Fisheries.
Changes to fish populations could also mean turmoil for the fishing industry, Cheung explained at a news briefing this afternoon. According to unpublished data, tropical countries such as Indonesia may experience the greatest disruptions. Not only will ranges shift considerably in these regions, but countries there tend to have relatively few economic resources to adapt their fishing fleets. In contrast, Norway will see fishing yields increase as more species migrate into its territorial waters.
The Canadian fishing industry will likewise benefit at the expense of their counterparts in the United States, where cod populations may fall by 50% by 2050. Overall, climate change may cause the continental United States to lose more than 15% of its potential catch by 2050. "The scary thing is that we're already seeing similar things happening now," Cheung said, noting that fishers on the west coast of the United States are already reporting shifts in sablefish populations.
--Erik Stokstad
