A common problem reported by pond owners is Bluegill stunting. Many people even avoid stocking this species because they have heard that this is inevitable. However, if Bluegill do stunt, it is a sign that there are other problems in the pond.
Ponds have a limited amount of food available for Bluegill, and as a result, the more fish you have the less they will grow. As an example, if you have 1,000 Bluegill in a 1-acre pond, they will grow at a certain rate. But if you have 10,000 Bluegill in that same pond, they will grow about 10 times slower.
Stunting happens when Bluegill over populate and "bottleneck" at a size that is too large for the Bass to eat, but too small for the fisherman to keep. The good news is that there are things you can do to prevent, or correct this.
- Maintain a strong population of the right type of fish predators to keep the Bluegill in check. Many people believe that introducing a couple Northern Pike is the solution, but they can actually make things worse. Large predators, like Northern Pike and Muskellunge, eat the size of fish that you want to catch, not the size that you want to eliminate. Also, they prefer to feed on long tubular shaped fish, like Largemouth Bass, instead of difficult to swallow Pan Fish. Largemouth Bass are the natural predator of small Bluegill and should be maintained at about 100 per surface acre. Channel Catfish stocked at about 50 to 100 per acre can also help keep the Bluegill in check, as will Walleye at about 20 per acre.
- Manage the fish population by harvesting the most abundant size class of the most abundant fish. If the pond has many 5” Bluegill and few Bass, then spend some time removing the 5” Bluegill. However, if the pond is loaded with 12” Bass and Bluegill are sparse, then harvest some Bass. This may sound like common sense advice, but many people are under the impression that catch & release fishing is always best. If done properly, catch & keep fishing can be a powerful management tool. See Largemouth Bass Stunting for more information.
- Do not let aquatic weeds or algae get too thick. Most weeds are actually quite beneficial for ponds because they filter the water, stabilize bottom sediment, and provide tremendous fish habitat. However, certain types of weeds can grow to be exceptionally thick in the summer, giving small Bluegill too many hiding places from Largemouth Bass and other predators. In the case of exotic nuisance weeds, like Curly-leaf Pondweed or Eurasian Watermilfoil, we recommend eradication followed by encouragement of native species. However, with native Pondweed species, Coontail, Elodea and many others, spot treatments with proper chemicals or partial harvesting with weed rakes can be very beneficial. In general, you want to maintain weed cover in roughly 25% of the pond. Please note that complete removal of weeds can be as bad of a fish management problem as thick weed cover.
- Do not harvest the largest Bluegill in the pond. Having large male Bluegill present inhibits the sexual maturation of other Bluegill. Immature fish grow much faster than mature fish because all the energy goes towards growth, and not towards reproduction. So, if the Bluegill in the pond are kept from becoming sexually mature, they will grow faster. Plus, there will be less reproduction, which will reduce the overall population, and thereby increase growth rates because more food is available per fish. See this example of Walnut Lake by the IL DNR for more information on this topic.