9646

• UCREFRP Catalog Number: 9646
• Author: Wiley, R. W. and R. S. Wydoski.
• Title: Management of Undesirable Fish Species.
• USFW Year: 1993.
• USFW - Doc Type: 335-354
• Copyright Material: YES

UNDESIRABLE SPECIES

347

14.5.2 Controlling Reproduction

Other biological controls include stocking hybrids that have little or no potential
to reproduce or altering the sex of fish by chemicals and heat to produce fish that
will never develop sexually or that will produce monosex individuals. Natural
reproduction of introduced fish species is sometimes considered undesirable. In
such cases, controlling reproduction by genetic manipulation is sometimes
warranted. In farm ponds, hybrid sunfish (limited reproductive capability) can be
established by two methods: (I) stocking FI hybrid sunfish directly into the ponds,
or (2) stocking parental fish of the correct sex to produce the desired hybrids
(Kurzawski and Heidinger 1982). In such situations, largemouth bass can control
any F2 hybrid sunfish since recruitment of F2 hybrids are minimal (Brunson and
Robinette 1986).

14.5.3 Forage Fish

Prey introductions are sometimes made in efforts to increase the growth of
stunted predators that are too small to be acceptable to anglers. However.
problems have also been caused by well-intentioned decisions to improve the
forage base for game fish. A classical example is the competitive interaction that
resulted from the introduction of redside shiners as possible forage for rainbow
trout in British Columbia lakes (Johannes and Larkin 1961). The introduction
failed because the behavior of the shiners resulted in ecological separation from
trout large enough to be effective predators while the shiners competed directly
for food with small trout.
Fish that are considered undesirable in some locations may serve as acceptable
forage in others. For example, Tui chubs provide the primary forage for a rainbow
trout subspecies in Eagle Lake, California (Burns 1966). In Pyramid Lake,
Nevada, Lahontan cutthroat trout prey upon Tui chub and the chub is not a
problem there. However, in other waters of the intermountain and western states,
minnows such as the Tui chub and Utah chub compete with stocked fingerling
rainbow trout. Consequently, they are controlled by stocking strains of trout that
are piscivorous, stocking warm or cool water predators, or through chemical
rehabilitation.
Some prey species are used more by predator species than others. For example,
rainbow smelt are considered to be better forage organisms for landlocked
Atlantic salmon in New England than alewife because of being more spatially
available. In some cases, the introduction of a prey species to serve as forage for
one game fish may result in competition with another. For example, cisco stocked
as prey for lake trout in Lake Opeongo, Ontario, competed with young small-
mouth bass (Emery 1975). Therefore, the biology of the species to be introduced
should be carefully reviewed. An ideal forage organism should be prolific, stable
in abundance, trophically efficient, vulnerable to predators, nonemigrating, and
innocuous to other species (Ney 1981).

14.5.4 Underexploited Fishes

Some conservation agencies have initiated programs to encourage the use of
less desirable fishes for food and sport. The common carp is one of the most
important problem fish species in North America because it is very prolific and
sought by few anglers. Miller (1972) offered suggestions on how to fish for