What physiological mechanisms allow the salmon to make the arduous journey to spawn?

Have you ever wondered, how salmon make that long arduous journey to spawn? How do they get the energy to jump up waterfalls, and how do they suddenly change their appearance from something you would eat, to something that looks more like a monster?

I learnt a fewer things from the recent conference on endocrine pathology instructed by Prof. Tom Rosol last week.

In salmon, there is increased hypothalamic-pituitary-adrenal activity, in a physiological condition known as "hyperadrenocorticism". In salmon, this goes into overdrive! Their cortisol levels peak and this enables them to catabolise their muscles, to give them fuel for their long journey without having to stop to feed. It’s like a fish on some performance enhancing drug!

But there are some side effects. These include increased pigmentation, atrophy of the skin (increasing the likelihood of skin infections), osteoporotic changes in the bone, marked growth of their jaws and accelerated premature ageing. In fact, a salmon ages in 2-4 weeks, as much as a human in 20-40 years!

By the time they arrive at their spawning grounds, these fish are beyond repair. Exhausted, emaciated and all beaten up, they die shortly after spawning.

Do you think it’s worth it?

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