VOA标准英语2011--Studies: How Whales, Fish Might Adapt To

Studies: How Whales, Fish Might Adapt To Warming Ocean

Two new science studies provide a glimpse of how some important Pacific Ocean sea creatures could adapt to a changing climate.

One study describes how gray whales successfully adapted to previous cycles of global warming and cooling. The second predicts a fish shift on the west coast of North America. The study suggests that some West Coast fishermen will need to pursue different prey 1 if the Pacific Ocean warms as projected over the next 50 years.

Nick Pyenson is a paleobiologist who curates the marine 2 fossil collection at the Smithsonian's Natural History Museum in Washington, D.C. The famous collection includes lots of creatures driven to extinction 3 by environmental changes. It also includes some of the long fossil record for gray whales, a species that still lives in the Pacific Ocean today.

"Grey whales fit into this question about ongoing 4 climate change," says Pyenson. He and his former doctoral advisor 5 from UC Berkeley wondered how gray whales survived through previous cycles of global warming and cooling.

"In the past two million years, the Northern Hemisphere has undergone dramatic changes with ice sheets going all the way down to Chicago and Seattle," says Pyenson. "In doing so, that sucks up a lot of the water that would be otherwise be put in the ocean and drops sea level dramatically."

According to Pyenson, historic sea level changes periodically expanded and closed off vast feeding grounds. He theorizes gray whales hung on through bad times by either migrating less, switching food sources or both. Even today, there are small numbers of gray whales that stay in one place and eat fish and krill, while most of their species migrate long distances and bottom feed.

"What we think is telling is that those who don't migrate are telling us about the range in behavior and what these animals can do ecologically."

Pyenson says that adaptability 6 bodes 7 well for how the whales may respond to future climate changes. He adds one caveat 8 though, saying the current cycle of human-induced global warming is developing faster and more powerfully than the historic episodes he examined.

Fish shift

In a separate study, a group of Canadian and American researchers examined how a warming ocean could affect fish common along the West Coast of North America.

The science team studied 28 fish species whose biology and distribution is well understood. Oceanographer Ric Brodeur of the NOAA Northwest Fisheries Science Center in Newport, Oregon, says the list includes salmon 9, smelt 10, sharks, pollock and sardines 11. Brodeur says the researchers simulated what could happen if the North Pacific heats up due to global warming.

"Because these fish are so mobile, they can move up and down the coast or inshore or offshore 12 to find the preferred temperature that they want."

The federal science agency, NOAA, predicts the ocean's surface waters off Oregon and Washington will warm about two degrees Celsius 14 over the next 50 years. Brodeur says that's enough to cause significant moves. A forthcoming research paper models how much. If you combine the home ranges of all the fish that the team studied, there's an average shift northward 15 of roughly 40 kilometers per decade. Over time, Brodeur predicts fishermen and seafood 16 consumers will notice.

"A lot of the species that we consider very important - like hake - things that are commercially fished here might be gone and replaced by other species that may or may not be commercially important."

Across Yaquina Bay from Brodeur's office, charter fishing boats unload sun-burned anglers. Veteran captain Robert Waddell says he's already seen some evidence of warm water species shifting northward.

"I've noticed in the last 12-13 years, we've been starting to see some marlin off and on out there and we've hooked them a few times," says Waddell.

Blue fin 13 tuna is another possible newcomer that could fill the vacancy 17 if, say, salmon left for cooler waters off Canada. Waddell is optimistic the local fishing fleet can adapt.

"People will make adjustments," he says. "Fifty years from now, we might be the marlin capital of the world. You never know."