Fishy tales

JUST ACROSS from where we have pitched our tent in a glade are the long dark shapes of salmon, their heads into the current of the stream. Now and then they contest their position and sometimes one will flap its tail before accelerating across and slightly out of the water before settling down.

Their dorsal fins are shark-like and they hold their place in the flow with no more than languid waves of their tail, so easily does the water flow by their torpedo body.

The Fraser and its tributaries are among the biggest spawning grounds in the world. Salmon born here in fresh water swim into the Fraser river and down to the bay at Vancouver, 1,000km away. There they encounter salt water for the first time. Confused but with no genetic choice but

to continue, they wait in the saline water, return to fresh water, come back to the salt and continue until they are ready to swim in the ocean. And then they swim and swim until they have crossed half the Pacific or, in extreme cases, until they reach the coast of Japan.

Nobody knows why they go, nobody knows what makes them return, least of all to within five metres of where they started. They navigate, extraordinarily, by their sense of smell. I had no idea that a fish could smell anything but every scent on the way out is memorised and then sought again on the way back.

Back in Vancouver Bay, they don't bother relearning fresh water. Nor do they eat. Time is against them. The change of water, the physical strain of swimming so far without nourishment, mean they arrive not only at half their weight but with their skin decaying and turning black with red and yellow patches. Their last days are near.

The females beat the river bed with their tales until they have created a hollow sometimes more than a metre deep. There they release their eggs, which fill a third of their body, hoping the depth will protect them from the current and from predators. The males wait in uncontested order of sexual maturity and release squirts of sperm which will stick to nothing but the eggs. It takes three males for every female.

The young are born so deep that they have no air in their body. They can swim only upwards. Their first act is to gulp in enough air so that, like a submarine, they can move it within themselves to swim horizontally, to rise and to dive. They feed on the decomposing bodies of adult salmon whose life cycle, once the seeds are sown, is complete. And then, in turn, the young swim out into the Pacific and start the process by which they too will die and rot in the place they were born.

How do we know all this? Because this evening we joined a guide beside the river, on the opposite bank from our tent, who told us the whole story.

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