July 2007 - Volume 68, Issue 7
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In this issue
NextGEN Departments
Counting Fish continued...
Age and Growth
In addition to recording the lengths of fish they catch, biologists often remove a few scales. Fish scales contain rings, much like the rings in the trunk of a tree, allowing biologists to determine a fish’s age.
We determine the growth rate of fish by comparing their age to their size. Slow growth in a fish population is often a result of an overpopulation of that species, or a shortage of food. Knowing the growth rate of fish populations helps us make decisions about the fishery.
Lakes and ponds generally have uneven fish production from year to year. Some years, the number of young may be small because of an abundance of competition from older fish, too many predators or a lack of food.
Natural reproduction of fish in any given year is strongly influenced by the fish already living in a body of water. Strong year-classes occur when conditions are right for lots of young fish to survive. These strong year-classes eventually affect future natural reproduction. Our fish sampling efforts reveal the year-class structure of various species in a body of water and helps us predict how good the fishing might be in future years.
We can also determine habitat conditions by noting the relative weight index of fish for their length. A fish with a relative weight of 1.0 is considered healthy, whereas .85 is on the skinny side and 1.2 is a fat fish that is finding plenty of food.
Sampling Anglers
During creel surveys, we’ll approach anglers and ask them for information about how long they fished and how many fish they caught. This harvest and fishing pressure data, combined with the information from our fish counting and sampling expeditions, gives us a good understanding of the dynamics of a fish population in a body of water.
We need this understanding in order to make adjustments to fish populations through length limits, daily limits, the setting of seasons, stocking and habitat enhancement.
Should you have a late-night encounter with
a Conservation Department survey boat, pull
over and say hello. We’re out there counting,
instead of casting, so that we can improve your
fishing. 
About This Article
Author
GREG STONER has been the Department’s
fisheries management biologist at Lake of the
Ozarks since 1991. He also assists landowners
with pond-related issues throughout Camden,
Miller and Morgan counties. When not at work,
Greg spends as much time as possible fishing in
the Niangua Arm of Lake of the Ozarks with his
wife, Sherri, and his kids, Alex and Katie, who
luckily all like to fish.
Photographers
CLIFF WHITE is a life-long Missouri resident. After nearly 10 years as a staff photographer for the Missouri Department of Conservation, Cliff recently took on management duties as Art Director. Now he supervises on an unruly gang of super-creative folks. In his spare time Cliff likes to play old-time folk and bluegrass music, float fish and chase the occasional turkey.
Department of Conservation photographer NOPPADOL PAOTHONG discovered his love and passion for wildlife photography in college in 1995. Born in Thailand, he came to the United States in 1993 to study graphic art before switching to journalism. He has worked as a full-time photographer at the Joplin Globe and the Springfield News-Leader, and has achieved more than 60 regional and national awards.
