Do Salmon Feed in Freshwater ?
Do Salmon Feed in Freshwater ?
By Patrick Mc Erlean
The question of whether or not salmon feed in freshwater is one that has fascinated anglers for many years. It’s viewed by many as perhaps the greatest of all of the many mysteries associated with this wonderful king of fish.
But is it really such a mystery, given all that we know about the migrating salmon?
To answer this question properly we need to take a look at the life of the salmon and its journey from egg to adult fish.
I guess the first question to ask is, “Did salmon always migrate from rivers to the sea”?
We can only speculate on the answer to that, but speculate is exactly what I’m going to do, so please bear with me for a couple of paragraphs!
I don’t think that it’s too big a stretch to presume that there was a time when salmon spent all of their lives in freshwater?
I’d guess that the species started out relatively small but that, over time, their average size got to the point where the available food supplies were no longer enough to sustain their growing population. At that point some of the more adventurous salmon would have begun the search for greener pastures, which eventually led to the sea.
Although the sea presented a bounty, the like of which they’d never seen before, there was a problem. Freshwater fish need salt secreting gills in order to survive in salt water. For that reason their initial forays into the sea were probably short and sweet, but as they evolved they could spend longer periods there. Eventually they adapted to sea life.
However, they couldn’t stay there indefinitely as salmon eggs cannot develop in salt water. That is one problem that evolution hasn’t found the solution to as yet, so the salmon have to return to freshwater to spawn.
Right that is enough of the speculation! Let’s look at what we know about the salmon’s life journey. I’m not going to get into the detail on when eggs hatch etc because there are lots of articles on that over the web. Suffice to say that salmon go through various stages of growth, from egg, to Alevin, to Parr, to Smolt and finally to adult salmon.
Perhaps one of the most wondrous aspects of this development process is that the salmon go through the various stages at varying rates! For example some parr will smolt within the first 2 years, whilst others will not smolt for 3 or 4 years.
You can even see this variation in fish that are all from the same batch of eggs. Likewise the smolts spend varying lengths in the sea. They even come back to spawn at various times of the year, e.g. spring, summer and autumn salmon.
This behaviour is also observable in kelts, which return to the sea at varying intervals. Presumably the reason for this is to guard against mass extinction? Even if a catastrophic event were to happen, not all of the fish would be impacted, thus ensuring the survival of the species.
A salmon leaves the river as a smolt when it has developed the salt secreting gills it needs to survive in the sea. At some point during its life at sea the salmon gets the urge to return to the river of its birth to spawn.
This urge triggers a physiological change in the fish, which results in it effectively switching off its feeding mechanism, much like those animals that hibernate for the winter months. Prior to this physiological change, the salmon has fed for a number of years at sea, building up its fat reserves, and it is now prepared to go without food until it returns from spawning. These are pretty much established facts at this stage and are rarely disputed.
So if a salmon switches off its feeding mechanism, why then does it sometimes take the baits and artificial lures presented by the angler? And why is it more likely to take in certain conditions? Some people say that salmon take because they are territorial, and this makes them strike out at the lure or bait, which is invading their patch. I honestly don’t think that this is a defensible position for a couple of reasons.
Firstly, why would a salmon feel threatened by another species, which is much smaller than itself? Surely they’d only be threatened by other salmon. Have you ever seen a bull chasing a bird which has landed in its field?
The second reason for debunking the territorial theory is because one of the most common times for a salmon to take is when it is resting between periods when it is running. Surely if a salmon was being territorial it would be much more likely to defend its patch when it gets to its spawning ground? In fact, as we all know, when a salmon gets settled into its spawning lie it’s even harder to tempt, if anything!
I believe that salmon have two main goals when they enter the river. The first is to spawn. The second is to conserve energy so that they can make it back to the sea to resume feeding.
In order to conserve energy, salmon will rarely move about in poorly oxygenated water. Of course there will always be the odd exception but in general that is the case. Water which is low or warm, or both, is often poorly oxygenated. Cold water can be well oxygenated but the fact that it is cold will stiffen up the fish’s muscles and therefore it will remain less active in order to conserve energy. After all it takes more energy to move about with cold, stuff muscles.
You might be asking, “What has the fish’s desire to conserve energy, got to do with whether or not it is a likely taker”? I’d say, quite a bit, because it has been pretty well established, mostly through observation, that salmon are much more likely to take when they are on the move (or at least when they are prepared to move).
Maybe so, but isn’t the real question, “Why does the salmon take at all, if it switches off its feeding mechanism before leaving the sea”?
Over the years there have been many studies carried out, which have shown that, when salmon are caught their stomachs are almost always empty. Some of these studies have also shown that, in almost every case the fish’s alimentary canal has shrunk from lack of use. If the fish was feeding in freshwater, that wouldn’t be the case.
So, case dismissed!
Salmon do not feed in freshwater!
Well, not quite because the fact still remains that fish do take bait and artificial lures into their mouth. Presumably they sometimes do they same with some of the other food sources the river has to offer.
It is my belief that the physical evidence is pretty clear; salmon do not feed in freshwater and the fact that they sometimes take an anglers offering, can be explained as a momentary lapse where they succumb to a deep seated urge to feed, much like that of an ex-smoker getting the urge to have a cigarette (even though they’ve been off them for a long time). I also believe that in most cases they snap out of this reflex action before they go ahead and swallow their quarry. Of course, there are the odd exceptions where the fish will swallow the bait (or food), but in my experience these instances are few and far between.
The only time a salmon truly feeds in freshwater is after a kelt has gone through the reverse physiological changes (i.e. turning on its feeding mechanism again), in preparation for its return to the sea. There are lots of people who have observed kelts feeding on hatches of flies and I contend that this only happens after they’ve gone through the change and are on their way back to the sea.
My scribbles here may not have solved the mystery of whether or not salmon feed in freshwater, but hopefully they’ve given you a new perspective on the question. There are still many remaining mysteries pertaining to the atlantic salmon, which we may never solve. For one, no one really knows how these fantastic fish find their way back to river of their birth (and mostly to the exact pool). Many have speculated that it’s some sort of chemical trail but like my ramblings above on the evolution of the salmon, this is purely speculation.
Patrick Mc Erlean has been fishing for salmon in Ireland, for over 30 years now, and has recently taken to writing about salmon fishing in the Emerald Isle. If you enjoy this article you can find similar material on his website at http://salmonireland.com/