Fish Swim North as Seas Warm
- From: chatnoir <wolfbat359a@xxxxxxxxxxxxxx>
- Date: Fri, 21 Dec 2007 14:37:03 -0800 (PST)
http://www.livescience.com/environment/071217-fish-warming.html
Fish Swim North as Seas Warm
By Jeanna Bryner, LiveScience Staff Writer
posted: 17 December 2007 08:02 am ET
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As their ocean homes overheat, some fish species are swimming North
again for the first time in hundreds of years to seek out cooler
waters.
That's according to several studies of archaeological material, tax
accounts, church registers and account books of monasteries, which
juxtapose marine life as it looked in the distant past with fish data
from today's warming world. The results, detailed in 14 papers in a
special issue of the journal Fisheries Research, shed light on how
global warming is impacting fisheries.
Global and regional climate models predict that air and sea
temperatures will rise by about 5.4 degrees Fahrenheit (3 degrees
Celsius) in the next 70 to 100 years.
Scientists studying ancient fish bones dated to a prehistoric warm
period (between 7,000 and 3,900 B.C.) in Scandinavia found an
abundance of warm-water species such as anchovies and black sea bream,
which are typically thought to reside much farther south. While these
species disappeared from the archaeological record when temperatures
cooled, many have returned to the waters around Denmark as
temperatures have risen over the last decade.
Another study looked at marine life during one of the coldest recorded
periods, the Little Ice Age, from 1675 to 1696. Results showed that
the cold-tolerant herring, flounder and eelpout formed the majority of
the catches in the Baltic Sea at the time. Warm-water species such as
perch and pikeperch, however, were less than 1 percent of the catches.
It's these warm-water fish that are now relatively widespread in the
Baltic, say the researchers. That suggests the fish have made their
way north as the waters became relatively balmy.
Fishing pressures also played a role in the health of fish
populations.
Recent increases in sea temperatures have been blamed for the plunge
in young cod survival in the North Sea. But this cold-water species
was abundant in Scandinavia during the prehistoric warm period. The
researchers suggest lower fishing pressure in the past kept cod
populations healthy. That means sustainable cod populations could be
maintained in the North Sea even during the climate change expected in
the 21st century, they say.
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