June 05, 2009
Northern Pike Age and Growth Data Will Help in Managing the Species
WATERBURY, VT -- Did you ever wonder how old that northern pike was you caught? How old was that 21-inch pike your child caught this year ice fishing? How about the 30-inch 8-lber you brought home for supper? How old was that monster 41-inch, 24-lb pike you saw in the winning spot at the local derby this past winter?
Vermont Fish & Wildlife Department fisheries biologists also want to know the answers to these questions. The department has been collecting biological data to learn more about northern pike age and growth rates in Vermont.
Some anglers may not think much about how fast or slow fish grow, or how old a big fish is. But, fisheries biologists are very interested in this information because age, length, size at maturity, and growth rate data provide the basic information necessary to understand and manage fish populations. With these data, biologists are able to evaluate the health and status of a fish population, make decisions on how to best manage a species, and then recommend actions such as setting new creel or length limits that will change the abundance or age structure of a population in order to improve the quality of fishing opportunities.
So how do biologists figure out how old a northern pike is, and how much it grows each year? By removing a bone called the “cleithrum,” located between the gills and pectoral fin of the fish, a biologist can determine the age of the fish in years by counting the number of growth bands or rings on. This is just like counting the rings you see on a tree stump.
Figuring out whether pike are growing fast or slow is fairly easy. Determining how much they grow each year (inches per year) is a little more technical and difficult, but it is still pretty straight-forward. Cleithrum bones from northern pike and muskie are almost exactly 1/10th the length of the fish. For example, the cleithrum from a 35-inch pike will measure 3.5-inches in length. Knowing this, a biologist can take measurements along the cleithrum, from the point of origin to each spot where an age-ring crosses the length of the bone and determine how long the fish was at each age during its life.
How does this help us in managing pike? By determining the age structure and growth rates of Vermont’s pike populations, fisheries biologists can determine what the "minimum ultimate size" is for any of Vermont’s pike populations. This is the length we would expect 99 of the pike to reach if nobody was fishing for them. The estimation of “minimum ultimate size” allows biologists to assess the trophy potential of a pike population by determining whether or not a pike population could grow larger fish than are currently in the population.
The growth data collected from the ongoing northern pike study, combined with creel survey data, which provide a measure of total harvest and harvest rates, will provide the information needed to determine if there are opportunities to develop fisheries for trophy size northern pike.
Northern pike populations in some Vermont waters may be able to be managed so there are more big fish available to anglers.
State fisheries biologists are conducting a survey on northern pike fishing regulations to determine what anglers’ opinions are on current regulations and potential regulation changes. The biologists also want to know what anglers want for northern pike fishing opportunities.Here’s how you can help. If you are going to keep a northern pike to eat, please remove the cleithrum and send it to the Vermont Fish & Wildlife Department so the fish can be aged. This is easy to do, and it only takes a minute or two. The department website includes instructions and forms at www.vtfishandwildlife.com\pike.cfm. A cleithrum from each fish should be put in a plastic bag and packaged with the date and location of the catch, the length of the fish, and the weight of the fish if possible