For years, it was one of the great mysteries of the natural world. Why do salmon of all kinds travel over such great distances and brave so many dangers to spawn in the exact place of their birth, only to die of exhaustion shortly afterwards? Simple, says Professor Donald Hancock of the Department of Zoology at Oxford, it's because they are 'fucking morons'.
Species of the family Salmonidae, Hancock explained yesterday, are mostly anadromous: they are born in fresh water, migrate to the ocean, then return to fresh water to reproduce. Those who survive infancy spend their first five years living in relative safety and comfort in the deep ocean, they inexplicably go back to where they started.
'In the process, they swim upstream against powerful currents, often leaping into the air many times in an attempt to navigate waterfalls. Predators - grizzly bears and eagles in Canada, fat blokes sitting in deck chairs drinking beer in Britain - lie in wait for them. At the end, those who are left lay or fertilise their eggs and invariably conk out on the spot,' said Hancock. 'Retarded or what?'
Some have contended that the salmon's migratory instinct is down to a mysterious force called olfactory memory. They believe that the river each fish was born in has a chemical signature that summons them home over thousands of miles. However, chemists argue that the sheer amount of fertiliser and other pollution dumped in rivers all around the world mean that this process should have stopped working and that therefore it all comes down to mindless conformity.
'The simplest explanation is usually the best,' Hancock said. 'These animals have brains the size of an amoeba's dick, so it's hardly surprising they are such a waste of smelt. And as for cod, they just sat there in the ocean for millions of years getting tastier by the day and waiting for us to make nets big enough to catch them? Absolute numpties, the lot of them.'