Would I be right in thinking that this would have the opposite effect? I am sure I read somewhere that the best control of pike numbers is big pike.
Hi Robert,
There have been extensive studies on this, many of which are available online.
There is a rather good book that was published a while back called The Predator Becomes The Prey. In it there is a chapter dedicated to your question.
In brief, once a water has established a healthy Predator/Prey balance, a natural biomass occurs. It fluctuates year on year but effectively, there is a balance and there is a maximum number of "pounds per acre" of fish that can be sustained in a healthy balance. The balance forms a nice "triangle" with a couple of big pike at the top, tapering out to an abundance, but controlled number of prey fish.
However, remove a number of large females via, say, a netting programme, and you get a gap. The predators and prey rush to fill that gap! The young pike usually fill the gap first, because they are one of the earliest spawners. By the time the other fish have spawned, the baby pike will be big enough to chomp fry.
Because there is an abundance of fry, the pike rapidly grow, forcing the predator/prey relationship out of balance.
After a couple of years you now have a large number of surviving pike in the 3-6lb range...and they are now big enough to make an impact on, lets say, brown trout stocks. This changes the "triangle" into a "bloated" shape, with the tip much flatter and the sides bowed out.
On top of this, big female pike like nothing better than chomping on a smaller male pike. Large females are lazy fish. They scavenge, hence dead baiting is successful, or they will take a large prey item (Pike, duck, horse
) and spend time digesting it.
Tagging and tracking programs over a decade on loch Lomond showed that the really big females (30lb+) ate 3-10 times a year. Food tended to be a large item, and the pike would then sit just below the thermocline, slowly digesting the prey item in the much cooler water. its different on shallow lowland water, they are more active, but still prefer fewer large meals than chasing around after agile fish. wasting energy.
So, as a few years pass, we now have an abundance of smaller pike, fewer prey fish, but a lot of female pike now turning cannibalistic. (males stop growing about 8-10lbs in weight, females continue to grow). This starts to change the triangle again. What you end up with is a high number of very big pike, preying on an increasingly diminishing number of average pike, meaning there is an explosion of prey fish! The triangle now has a very different look with a high number of big fish, a pinched "middle" and a very wide prey base.
There are good examples of this in action. Places like Chew stopped netting a good few years back, they saw an increase in smaller pike, so started stocking bigger trout. Now Chew is producing large numbers of very big pike as the balance is in its third phase (lots of big fish) and the roach, bream and other spawning stock has increased.
However, as time marches on, as long as man does not interfere, waters will return to a balance.
So, in summary, remove large pike, you get a short term benefit, followed by a sudden explosion of small pike for 2-6 years, followed by a period of very large pike, then back to "normal". This is far more noticeable in non stocked waters.
Sorry its long winded, but I hope it answers your question.
