Global warming has serious consequences for the international fishing community — and for humanity. A study published in the prestigious Proceedings of the National Academy of Sciences indicates that individual fish have lost half their average body mass, that fish populations have thinned drastically, and that smaller species are starting to dominate European fishing grounds. Although overfishing may have played a role, the long, steady increase in ocean temperatures caused by global warming takes the lion’s share of the blame.
“It’s huge,” said study author Martin Daufresne of the Cemagref Public Agricultural and Environmental Research Institute in Lyon, France. “Size is a fundamental characteristic that is linked to a number of biological functions, such as fecundity — the capacity to reproduce.”
Marine biologists know that smaller fish have fewer innate resources, and tend to produce fewer eggs, and so fewer offspring. Lower individual weights also mean that the same number of fish feed fewer people and, by extension, fewer predators along the food chain. This study builds on previous work and establishes that marine life has shifted migratory and breeding patterns in response to rising sea temperatures, and that warmer seas seem to favor smaller breeds of fish.
Dr. Daufresne and his colleagues examined long-term surveys of fish populations in rivers, streams and the Baltic and North Seas and also performed experiments on bacteria and plankton. They have determined that many individual species have lost 50 percent of their mass in just 25 years, and that stocks have declined by 60 percent.
While commercial and recreational fishing does affect some of the fisheries studied, it “cannot be considered as the unique trigger” for the changes in size, Daufresne’s group found. “Although not negating the role of other factors, our study provides strong evidence that temperature actually plays a major role in driving changes in the size structure of populations and communities.”
Editor’s Note: I grew up watching Jacques Cousteau and National Geographic on television which filled with a deep and abiding awe for the creatures that share the world with us. The worst case scenarios suggest that warming this century will place 50 to 70 percent of the world’s species at risk.
Is this really the world we want to leave our children and grandchildren?
And then there is this grim projection:
http://www.guardian.co.uk/environment/2009/jul/07/coral-attenborough
Coral reefs are the foundation of life in the ocean, just as trees are on land. Both are careening towards extinction, and with them will go many – no, most – other species.
Wonderful blog, by the way!