Ocean Fish Identification Chart

Canadian scientists have devised a new scale for measuring ocean change – the fish. They have used the changing make-up of the global fisheries catch to detect the signature of global warming.

In a warming world, fish that find the sea temperatures too hot for comfort could move north or south, away from the tropics, or to deeper and therefore cooler waters.

Although oceans are warming, and the chemistry of the seas gradually changing, William Cheung and colleagues at the University of British Columbia report in Nature that it has not been easy so far to detect any evidence of change for these reasons: because over-exploitation of the traditional fishing grounds, and greater pressure on more distant and deeper waters, made it difficult to identify any climatic effect.

But the researchers tried a different approach: they calculated the temperature preferences of fish species – confusingly, they called this the mean temperature of catch – and then they analysed the annual haul of 990 species across 52 large marine ecosystems between 1970 and 2006.

They accounted for possible confounding factors (overfishing being one of them) and then came up with a “fish thermometer”, on the argument that, just as changes in the pattern of tree growth rings would expose the climate history of a forest, so changes in the pattern of fish catches would tell them something about ocean temperatures.

Their new scale of measurement revealed that overall, oceans were warming at a rate of 0.19°C per decade, and in the non-tropical regions even faster: at 0.23°C per decade.

Fewer fish, more hunger

In some regions, the rate of change was much faster. The north-east Atlantic, for instance, has been warming at 0.49°C a decade as measured by the fish-scale thermometer, even though sea surface temperatures showed only a 0.26°C rise as measured by other instruments. Warm water species are on the move, to what were once considered cooler seas.

Catching WHITES -2

2004-12-18 13:02:57 by WHites

Lake whitefish generally spawn in the late autumn just prior to freeze-up in shallow water (often less than 25 feet), usually over a hard or stony bottom, but sometimes over sand. Spawning can occur under the ice in some lakes, however. What does this tell you? Well, like most fish, spent adults are hungry following the spawning season. Often the best lake whitefish catches are shortly after they spawn in the month of December, just when the ice is safe to travel on. Use caution on ice and always test the conditions. Never walk on ice that is less than four inches thick and don't drive on ice that is less than 12 inches thick

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