Fishing Revisited

My Dad grew up on the famous Restigouche River, and as a child in the 1930’s, I can remember him coming home after a day on the river - and when he'd open up the trunk of his car with a flourish, there would be 5 or 6 beautiful 30 to 40lb. salmon gleaming in the sun!!  I’ve read that the top 10% of anglers catch an amazing 90% of all fish, and I’m sure my father was among that top 10%! 

Even so, I think he would have been intrigued if he had known that the fish’s blood circulation system is very different from land creatures who have lungs. When we fill our lungs with air it oxygenates the blood which then goes directly to the heart from where it circulates to the rest of the body.  

As the simple diagram on the right shows, a fish basically has a closed-loop circulation system with its heart pumping the blood in a single loop around the body. Starting with the gills that act as the fish’s lungs, the red lines in the picture show where the oxygen-carrying blood flows. The oxygen is depleted as the muscles work and the black lines show places where little or no oxygen is left in the blood. But the heart itself is a muscle, and if the fish is using it's muscles fighting hard to get free of a fisherman's  hook, all the oxygen is used up and when the blood reaches the heart, it actually stops so the fish cannot move until the heart recovers and again supplies them with an adequate oxygen supply. 
Any fisherman who has fought to land a large fish will recognize the pattern of keeping the line taught to play the fish and reeling it in when the fish is recovering. 

You have little chance of landing a salmon unless you always keep your line tight - but not so tight that it breaks! If a light ‘leader’ line that is less visible in the water is used [my father would have used a 6 to 8 lb. test line], a big salmon can easily break it. So you have to let the salmon run as many times as it can with just the right tension on the line to deprive its heart of oxygen temporarily so that you can reel it in part way. A big fish can sometimes take up to an hour to land. And after all that, if you are trying to scoop up half dead fish with a net, it is easy to lose it as it comes to life and takes off. 

As fishermen say, 'tight lines.' Rie