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DFO report: Warming seas hard on salmon
Sandra McCulloch, Times Colonist June 08, 2006
Salmon and herring populations off southwest Vancouver Island will suffer next year and the year after because of the persistence of unusually warm temperatures in the ocean, warns a State of the Oceans report, released Wednesday by Fisheries and Oceans Canada.
"A lot of the fish we have here live a long time so they're adapted to periods of warm water and periods of cold water and they do just fine through those. What they're not adapted to are these long periods of really warm conditions," said Ian Perry, one of the report's authors and a biologist at the Pacific Biological Station in Nanaimo.
Warmer sea temperatures reduce the mixing of nutrients and cut the production of phytoplankton, which are the bottom of the food chain. While the temperature change is bad news for salmon, which prefer cooler water, it's good news for other fish species such as sardines and Pacific hake, the report said.
The warmer water means predators will likely eat young salmon emerging from the rivers, reducing the numbers able to return and spawn, Perry said.
Warm oceans will also lead to the planet getting warmer, said Perry, "because the oceans store heat. And even though the atmosphere might cool, that heat is still going to be in the ocean. It takes a long time for it to cool down."
Waters off B.C. are attracting species that normally live off the California coast, such as sardines, mackerel and a voracious eater of many fish, the Humboldt squid, said Perry.
Scientists are surprised that the oceans have stayed warm for the past three years.
"We had actually expected it to cool," said Perry, noting a strong cool period lasted from 1999 through 2001.
"We thought we were going back to conditions that were good for salmon and that we've seen through the 1980s and early 1990s.
"The surprise has been that 2003, 2004 and 2005 have all gone back to warm conditions."
Sea temperatures off B.C. down to 175 metres in depth remain 0.5 to 5 degrees Celsius warmer than in 1990-1996, the report said. The warming trend puts the sea temperature off Tofino at 13 to 14 degrees Celsius, said Perry.
The temperature of oceans globally last year was slightly cooler than in 2004 but still ranked as the seventh-warmest year on record since 1880. The ocean has been warming on average by 0.13 degrees Celsius per decade since 1880.
"Warm conditions mean things are going to be different than we have had them in the past," said Perry.
- On an annual basis, the Pacific coast was warmer and drier than normal in 2005.
- Sea temperatures maintained warm conditions in 2005 in all B.C. marine ecosystems.
- Warm sea temperatures reduced the supply of plant nutrients into surface layers of the Pacific Ocean, thus reducing the production of phytoplankton, which is the base of the marine food web.
- The growth of juvenile coho salmon on the west coast of Vancouver Island during spring to fall was the lowest since these observations began in 1998.
- Warm-weather migratory species such as Pacific hake and Pacific sardine were abundant in B.C. waters during 2005.

 Other warm-water species not typically seen in B.C were also spotted.
Source: State of the Oceans 2005



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