Wednesday, April 6, 2011

Fraser River too warm for sockeye

Sockeye salmon at risk of overheating due to climate change

The Globe and Mail: Sockeye salmon in the Fraser River are facing such critically warm water in the summer that populations will either have to adapt or die as climate change pushes temperatures even higher, according to new research at the University of British Columbia. With oceans, lakes and rivers warming worldwide, the study holds a warning that fish stocks are facing increasingly dire environmental challenges...

Researcher Erika Eliason found... that sockeye, which migrate up to 1,200 kilometres in the fraser, are already 'near their upper limit' for warm water and any further increases could lead to the disappearance of some population... There are more than 100 sockeye populations in the Fraser and over time they have evolved in response to the specific environmental conditions they face during migration...

Ms. Eliason said it isn't known how long it takes a population to change physiologically to adapt to environmental conditions -- and it might not be possible for any of the populations to change fast enough to survive in the long run... The Fraser has warmed by about two degrees over the past two decades and the trend is expected to continue. The river is usually over 19 degrees in the summer, and often hits highs of around 21.5 degrees.

'They are all near their upper limit... 21.5 degrees C is already higher than the optimal temperature for every single population in the Fraser, she said. 'There is not much room there, for anybody.'

Postmedia News: The salmon... appear to undergo 'cardiac collapse' when river temperatures get too high... The researchers found that the sockeye that spawn near the coast and have a much easier migration route, have much smaller hearts and less resilience than fish that make more gruelling trips... Sockeye that head farther up the Fraser have hearts almost 50 per cent bigger than the weaker populations, and had more developed cardio-respiratory systems that could handle hotter water.

In recent years the scientists say between 40 and 95 per cent of some sockeye populations have died en route to their spawning grounds... 'We think that fish can't swim at hot temperatures because the fish can't provide sufficient oxygen to their swimming muscles,' [Eliason] says. 'We think this is because the heart can't pump sufficient blood.'
Image source here.