Intelligent Harvesting

In Bone Lake....

It's a Question of Balance

Craig Sandell 2012

There have recently been movements to increase the minimum size limit for Musky to 48, 50 and even 55 inches, thereby assuring an almost 100% catch & release. For those of us who suffered through the "Bad Old Days" when almost every Musky caught was kept, the concept of a 100% catch and release regulation seems to make sense. There is, however, sound reasoning that indicates that intelligent harvesting of Musky in a fishery will actually make that fishery a better fishery.

This reasoning is based upon the concept known as "Carrying Capacity." We all deal with the concept of "Carrying Capacity" every day. If you overload your truck or car you may break a spring, if you overload the electrical outlet you may blow a fuse and if you overload a fishery you may end up doing more harm than good.

Preliminary findings from the Wisconsin DNR's study of Bone Lake brings the concept of carrying capacity into a clearer focus. Bone Lake has enjoyed the benefit of Musky stocking for many years. The larger size of the fingerlings released has increased the survival rate of stocked fish. Consequently, the Musky population is robust. However, the rate at which Musky are growing is less than what was expected. Indeed, the average size of mature musky has actually declined. Bone Lake is right on the cusp of having too may fish chasing too little forage.

As another example, lets take one of the Wisconsin lakes where a 50 inch limit has been imposed for no other reason than to attempt to create a "Trophy Fishery". Lac Courte Oreilles is identified by the DNR as a Class "B" lake. That means that the lake is not capable of sustaining a completely viable Musky population without some stocking intervention. The pyramid chart shown here demonstrates a normal profile for a fishery and, for the purposes of this discussion, we will assume that Lac Courte Oreilles was balanced in this manner prior to the 50 inch size limit. The Musky at the top of the pyramid represent a population of top line predator that is small enough so as not to put undue stress upon the other resources of the fishery. The population of the mid-level predators is larger than the Musky population but not so big as to overtax the forage base that occupies the lowest level of the fishery pyramid. As long as this fishery maintains a relative balance between these pyramid levels, the fishery will be healthy and productive within its capacity.

Now that Lac Courte Oreilles has a 50 inch Musky limit, the harvest of Musky will be significantly reduced. The Musky that are the "eating machines" will not be culled and will therefore place pressure upon the mid-level predators as they seek to satisfy their appetite. (This has been seen in Bone Lake.)

The hour glass chart shown here is a projection of how the balance of the fishery may be distorted over time. As more and more Musky eat more of the mid-level predators, they make it more difficult for the mid-level predators to establish a mature spawning population. The numbers of the mid-level predator will decline making it harder for Musky to catch the fish they must in order to have normal growth patterns. As mid level predator numbers decline, the forage base will undergo a population expansion. These increased numbers will eventually place a greater burden upon the ecological system of the fishery. Unless the mid-level forage base is replenished, the fishery will move toward an imbalance that will eventually cause the collapse of the fishery.

True, mid-level predators can have their populations increased by stocking. Of course, stocking is an expensive activity and with the imbalance at the top of the food chain, the only thing that stocking will accomplish will be to provide more food for the Musky. The other solution is to harvest some of the Musky and relieve the stress upon the mid-level predator population thereby placing us right back where we started before the 50 inch limit was imposed.

Although most Musky anglers consider themselves 'extremists' when it comes to conservation of the Musky resource through a devotion to catch & release; it appears as though, in some instances, conservation and care of the fishery is better served through the application of intelligent harvesting.