Deep sea fish growing slower due to global warming
Rhett A. Butler, mongabay.com
April 23, 2007




Changes in ocean temperature have altered the growth rates of commercially harvested fish over the past century, according to a new study published in this week's early online edition of the Proceedings of the National Academy of Sciences (PNAS).

Analyzing the ear bones of 555 commercially caught fish to determine age, the researchers, led by Ronald E. Thresher of CSIRO-Australia, report that warmer temperatures in the southwest Pacific Ocean have enabled shallow-water fish to grow faster, perhaps making them more resilient to commercial exploitation. At the same time, deepwater regions have cooled, reducing the growth rates of fish species found at depths greater than 1000 meters (3300 feet), by 30 percent relative to 50 years ago.



Orange roughy (Hoplostethus atlanticus). Drawing by former FishBase artist Robbie Cada.
While the results have potential implications for commercial ocean fisheries, the researchers say the trend might be temporary.

"With increasing global warning, temperatures at intermediate depths are likely to rise near globally... suggesting that... the decrease in growth rates for the deep-water species could slow and even be reversed."

Deepwater fish tend to be longer-lived than shallow water dwellers--some species, like the warty oreo (Allocyttus verrucosus) and orange roughy (Hoplostethus atlanticus), may live to be more than 130 years old. Their slow reproductive rate means they are especially vulnerable to overexploitation and conservation groups have recently warned that a number of deepwater fish stocks are at the point of collapse.

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CITATION:
Rhett A. Butler, mongabay.com (April 23, 2007).

Deep sea fish growing slower due to global warming.

http://news.mongabay.com/2007/0423-fish_climate.html