TO STOCK OR NOT TO STOCK
Galen Jons, Fisheries Biologist
Stocking fish has always been a popular tool used by fisheries managers for enhancing fisheries. However, sometimes this tool is more popular with anglers than it is with biologists, because lakes don't always need to be stocked.
We hear many comments from anglers that we need to stock a lake because the only fish they can catch are small ones. There are a couple of problems with this, as we generally can't stock large fish. In order for our hatcheries to raise large fish, they need a LOT of pond space, which they don't have. Additionally, many predator fish, such as largemouth bass, striped bass and hybrid striped bass, will become cannibalistic and eat each other, leaving a large hatchery pond with just a few fish. Therefore, we can only stock small sizes (fingerling or fry) of most types of fish.
Now, if we stock small fish into a lake that already has numerous small fish, several things can happen. It is likely that overall numbers of fish in the lake will stay the same, and additional fish will simply be eaten by predators (expensive fish food!). Another possibility is if all fish survived, then we are merely increasing numbers and competition among all small fish, resulting in slower growth and a longer time to reach legal harvestable size. So, in this case, stocking actually compounds the problem rather than helping it.
Following is a primer on the why's and wherefore's of fish stocking and why we (the Texas Parks and Wildlife Department) may or may not stock a particular species into a particular lake.
Largemouth bass: This is Texas' most popular sport fish, and our hatcheries' production reflects that. However, it may come as a surprise to many anglers that we usually do not stock largemouth bass to increase numbers of fish in a lake. There are only a few situations in which we could significantly increase those numbers. We may stock to supplement natural reproduction in lakes lacking spawning habitat (rare in Texas lakes) or in cases where the adult brood stock in a lake is extremely low. A situation where adult brood stock is very low is also quite rare, but may occur in circumstances such as prolonged drought where water levels are dropping over several years. Bass will still spawn during a drought, but there is generally little or no cover for bass fry, so natural mortality is extremely high. Over a period of several years, this can lead to a severe reduction in bass numbers. Other situations where we may stock to increase numbers would be in a lake that has no bass (such as a new or renovated lake), or lakes that suffer very heavy fishing pressure and have little or no reproduction, such as some power-plant lakes.
The main reason we stock largemouth bass is to influence genetics. Florida-strain largemouth bass have been stocked into most of Texas' public lakes over the last three decades. The results of these stockings have shown up in a tremendous increase in overall size and numbers of trophy bass being caught. Additional stockings of Florida-strain largemouth bass are necessary to maintain Florida-strain genetics in the bass population and improve an angler's chance of catching a trophy bass.
Crappie: These fish are very popular throughout Texas, and many anglers want them stocked. However, stocking crappie has been shown to do little or nothing to enhance natural populations. Because of this, our hatcheries do not even raise crappie, although they would probably do so to stock a new large reservoir. If we have a new or renovated smaller lake that has no crappie, we may introduce them with management stockings (where we move fish from another lake).
Crappie populations are highly cyclic, and seem to be unaffected by stocking. We've seen lakes heavily exploited by anglers that would produce fantastic crappie fishing year after year, then suddenly crash for no apparent reason, only to build back up again a few years later. There are few things that fishery managers can do to enhance crappie populations; unfortunately, stocking generally isn't one of them.
Stripers/hybrid stripers: These fish, for the most part, will not spawn in Texas lakes, so they need to be continually stocked to maintain their populations. Survival of stocked fish is usually quite good, as they are stocked into open-water environments that have few predators. White bass, a cousin to the stripers, will readily spawn in Texas lakes, and there is usually no need to stock those fish.
Catfish: The jury is still out on catfish stocking. In most Texas lakes, catfish will readily spawn and produce small catfish fry (way more than we could ever stock). However, a few lakes may be lacking in proper spawning habitat, and may need additional stockings to enhance populations.
Some lakes typically have low numbers of channel catfish. This is usually because of predators, such as largemouth bass and flathead catfish, eating small channel catfish. In cases such as this, stocking will not help unless we could stock larger channel catfish.
Our hatcheries can and do raise larger catfish (8 - 10-inch) for our urban ponds. While these larger fish are better able to withstand predation, they are mainly stocked in an effort to provide a put-grow-and-take fishery in urban lakes that experience heavy fishing pressure. Unfortunately, our hatcheries can't raise enough of these larger fish to stock our big lakes.
We are also looking into possibly enhancing the genetics of catfish populations, much like we have done with largemouth bass. It may be possible to increase the overall size and growth rates of existing channel catfish populations by stocking strains that grow faster and larger than the strain of fish that is already in the lake.
Texas Parks and Wildlife Dept.
5325 N. 3rd
Abilene, TX 79603
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