by Staff Writers
Paris (AFP) June 22, 2011
A decade-long study of the Pacific's biggest predator species has pinpointed the food hotspots and migratory avenues which lure them in seasonal patterns, Nature reported on Wednesday.
Biologists tagged 23 species, from mammals such as whales and seals to sharks, tuna, albatrosses and turtles, which are considered "apex predators," meaning they are at the top of the marine food chain.
The animals, monitored throughout the last decade, headed for biological hotspots like the California Current System, flowing southwards along the US West, where a mix of surface and deep waters brings an upwelling of tiny marine plants and crustaceans.
Another place for congregation is the North Pacific Transition Zone, a boundary between cold sub-arctic water and warm sub-tropical water located between Hawaii and Alaska.
"These are the oceanic areas where the food is most abundant, and it's driven by high primary productivity at the base of the food chain," researchers Barbara Block of Stanford University and Daniel Costa of the University of California at Santa Cruz, said in a press release.
Block likened such areas to Africa's Serengeti Plain, whose vegetation is the building block for a dazzling array of species.
The investigation also showed some predators may spend all their lives in one food-rich zone but others can cross the ocean to get to the banquet.
Differences exist even in closely-related species: some tuna species, for instance prefer particular water temperatures, which prompts them to seek out specific habitats.
Amongst the patterns, though, was some intriguing variability.
Bruce Mate, director of the Marine Mammal Institute at Oregon State University, said he and colleagues tracked a fin whale for more than a year.
"It did nothing that we expected," he said. "Usually, we think large whale species go south for the winter and north in the summer, but this whale spent its winter in the Gulf of Alaska and didn't go south until spring when it went as far south as the tip of Baja (California) -- but returned back to the Gulf of Alaska without stopping anywhere."
The programme, called Tagging of Pacific Predators (TOPP), gathered 75 experts from five countries, in what is being called the world's biggest bio-logging study.
They attached 4,306 electronic tags, whose data will take years to analyse.
Put together, the information should help conservation strategies by pinpointing the movements of species at risk. Fishing on migratory paths, for instance, could be restricted to help vulnerable species.
"Using satellite observations of temperature and chlorophyll concentrations alone, we can now predict when and where individual species are likely to be in a given ocean region and begin to understand factors that control their movements," said Costa.
"This is fundamental to the concept of ecosystem-based based management."
In a separate report issued on Monday, a consortium of marine biologists said the world's oceans were heading towards a mass die-out to a degree last seen tens of millions of years ago.
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Fastest Sea-Level Rise in Two Millennia Linked to Increasing Global Temperatures
Washington DC (SPX) Jun 21, 2011
The rate of sea level rise along the U.S. Atlantic coast is greater now than at any time in the past 2,000 years--and has shown a consistent link between changes in global mean surface temperature and sea level. The findings are published this week in the journal Proceedings of the National Academy of Sciences (PNAS). The research, funded by the National Science Foundation (NSF), was ... read more
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