Stunting Fish Populations
The federal and state governments designate seasons for different types of fish and limit the weight and number that fishermen can take home. Such fishing regulations are necessary to protect the health of underwater ecosystems because if one fish population becomes depleted, its absence will affect others in the area. The same principle certainly applies to panfish. Wildlife agencies are particularly concerned with the balance between the bluegill and largemouth bass. Bluegills reproduce exponentially fast, and a single female may lay as many as 40,000 eggs in one year. The largemouth bass that feed on panfish prevent streams or lakes from being overrun with bluegills. But things can get thrown out of whack when anglers begin dipping their lines into that habitat.
Panfish are incredibly popular types of fish to catch, but anglers may toss them back in search of a more sizable haul. If fishermen repeatedly go for the bass instead of the bluegills, overfishing can lower the panfish predator population. Without the bass around to eat them, the number of panfish in the water booms. And when it comes to panfish, more isn't always better.
When the small bluegill, bream, crappie and other panfish experience unrestrained population growth, stunting occurs. With the proliferation of the panfish, food competition among them intensifies. Some of them will starve or even eat each other, but overall, the panfish adapt to surviving off of lowered amounts of food.
Consequently, a shrunken diet stunts body development. A fish's growth is primary controlled by its GH hormone. The external environment can impact the concentration of GH in a fish's bloodstream, and, therefore, its growth rate. Ironically, stunted fish have more GH released in their bodies than regular fish. However, the stunting also makes them resistant to the hormone, thus limiting their growth [source: Evans].
So while panfish are naturally little fish, stunting produces even smaller ones. At the same time, the greater number of panfish generates more nutrient-rich waste that promotes underwater weed growth [source: Garling]. Added vegetation then provides extra hiding spaces from predatory fish, compounding the negative feedback cycle.
If stunting occurs, it's a tricky process to stop. Ultimately, the problem is solved by reducing the panfish population drastically. That can be accomplished in a number of ways, such as poisoning the panfish, introducing more predator fish or fishing them out. Due to their accelerated reproduction rates, fishing out enough panfish to make a difference can prove an uphill battle. It may be necessary to remove as many as 95 percent of the stunted fish in the area to alleviate the problem [source: Garling].
Another possible solution to the stunting problem is reducing the angler activity to allow panfish to grow larger before being fished out. A study conducted by the Wisconsin Department of Natural Resources found an inverse relationship between fishing frequency and panfish body mass [source: Beard et al]. Following similar logic, the Pennsylvania Fish and Boat Commission recently instituted new regulations for enhancing panfish size. The rules have curbed the number of panfish that anglers can take home and raised the minimum allowable size [source: Frye]. So far, results in the 18 enforced fishing areas have been mixed. Evidently, stumping a stunted pond or lake isn't an easy task to reel in.
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More Great Links
- Beard Jr., Douglas T. et al. "The Effects of Simulated Angling Regulations on Stunting in Bluegill Populations." North American Journal of Fisheries Management. May 1997. (Nov. 10, 2008)http://afs.allenpress.com/perlserv/?request=get-abstract&doi=10.1577%2F1548-8675(1997)017%3C0525:EOSARO%3E2.3.CO%3B2&ct=1
- Evans, David H. "The Physiology of Fishes." CRC Press. 1998. (Nov. 10, 2008)http://books.google.com/books?id=rHyPWriet7gC
- Frye, Bob. "Panfish regulations bring mixed reviews." McClatchy-Tribune Business News. June 29, 2008.
- Garling, Don. "My Bluegills Are Stunted." Michigan State University Extension. April 2002. (Nov. 10, 2008)http://web1.msue.msu.edu/wildlife/E-1776.pdf
- "New Mexico Panfish." New Mexico Wildlife. Updated Sept. 24, 2008. (Nov. 10, 2008)http://www.wildlife.state.nm.us/recreation/fishing/warm_water_species/Panfish.htm
- "Sunfish Management." Minnesota Department of Natural Resources. (Nov. 10, 2008)http://www.dnr.state.mn.us/fish/sunfish/management.html