To provide sporting and recreational opportunities, state and federal wildlife departments began stocking the new reservoirs with fish. Some of the species stocked were not indigenous. Of these, some died out, while others became the dominant fishes within the ecosystem and soon became regarded as invasive species. Others found equilibrium with their new environment. The practice of stocking lakes and reservoirs is still common, although current methods are somewhat more in tune with environmental concerns.
Many of the newly introduced species grew in population rapidly and diminished the food supply available for other, less aggressive species. In extreme cases, state agencies created regulations requiring that certain species that are caught may not be returned to the waters alive. Although it is a controversial practice, it is not uncommon to see anglers destroy rough fish when they are caught, even if against waste-of-fish laws.
Some species that are nonnative may grow larger or become more prolific breeders when introduced into a new environment, due to differences in salinity, temperature ranges, natural forage, and water flow compared to the native habitat. If a fish is introduced into a new ecosystem that lacks the natural predators found in its native habitat, the potential for rapid population increase is also present.
Often, a fish that is considered rough in one country or region may be considered a delicacy in another. This is often due to cultural differences or simply tradition. In other circumstances, the environments are different enough to change the taste or quality of the fish as well. Often, fish that are caught in clear water have a less "fishy" taste than fish that are caught in stained or turbid waters.
The carp is a prime example. In most parts of the United States and Australia, carp are considered rough fish because they reduce the food supply available to more desirable fish such as catfish, largemouth bass, sunfish, bluegill and crappie, all which are considered excellent table fare. Carp were introduced to many lakes and reservoirs with mixed results. In some areas, their natural inclination to disturb the vegetation has increased the water's turbidity. Other areas have seen a population explosion of these fish, with an attendant decrease in the populations of native fish.
Recently, the carp's reputation has been changing somewhat in the U.S. with the introduction of Jackpot tournaments in which large prizes are offered for the largest fish caught. Unlike many rough fish, the carp can grow quite large and offers excellent sporting opportunity. Carp weighing up to 10 pounds are relatively common, but any carp over 20 pounds would be considered a trophy fish in most areas.
In contrast, in Europe the carp is highly prized for purely sport fishing and presents a fight comparable to saltwater redfish or bonefish. It is also prized as a staple eating fish in much of Asia and represents the largest source of protein in many developing countries. While carp caught in clear waters can be very palatable, many people from developed countries find the sheer volume of bones and difficulty in filleting the fish to be reason enough to not eat them. Carp caught in turbid waters can be very "fishy" tasting.
Within the United States, the bullhead family of fish are considered rough fish in the majority of regions, although they are eaten in some areas and can be quite palatable when caught in fresh water, again demonstrating the subjectivity of the term. Some may be eaten when taken from extremely clean waters or only eaten in limited geographical areas. Examples include Bullhead catfish (Yellow, Brown or Black, which are often called mud catfish), suckers (including the buffaloes) and carp.