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

345

Box 14.4 Important Factors that Must be Considered in Choosing a
Suitable Predator or Prey Species

I. Numbers of undesirable or unexploited fishes.
2. Size of the prey fish species.
3. Potential for use of forage organisms by sport fish predators.
4. Size of the water body.
5. Species and strains of predators available.
6. Size of predators at stocking and estimated survival based on size.
7. Stocking rates as well as timing and frequency of stocking.
8. Habitat suitability for the predator.
9. The desirability of the predator as a sport species.
10. Angler harvest of stocked game fish.
II. Control of the predator in the stocked water.
12. Native fish species (especially threatened and endangered fishes) that
may be impacted by the predator (e.g., hybridization, competition and
predation).
13. Potential for transmission of disease or parasites.
14. Fisheries management plan for the basin where introduction is to take
place.
15. Public preference.

such as sterile triploid grass carp has been very effective. However, many
biologists have opposed the use of grass carp because of the perceived potential
for adverse environmental impacts (see Chapter 12).

14.5.1 Predatory Fish

Biologists control fast-growing populations of forage fish or stunted sport fish
by stocking sport-fish predators. Various predator-prey combinations are used in
farm ponds to manipulate the carrying capacity for desired fishes. Variations in
predator and prey growth by latitude requires different approaches to pond
fisheries management as suggested for largemouth bass-bluegill (see Chapter 20).
In special situations, stocking of predators may improve sport fishing in waters
that contain overabundant and stunted fish populations. To be effective as a
management tool, predator stocking should (I) be cost-effective with respect to
culture cost, stocking rates, and survival; (2) result in survival to sufficient
numbers so anglers have a reasonable chance to catch them; (3) grow large enough
to be of interest to anglers; and (4) produce consistent fisheries so biologists can
reasonably predict the outcome of such stockings.
Almost all states and Canadian provinces use predators for biological control of
abundant forage fish. Some of the encountered problems include: (I) the predator
is not stocked at adequate density, (2) the predator reduces the desirable forage
fish resulting in reduced growth of the predator, (3) the predator becomes
overpopulated and stunted, (4) the predator causes declines of other sport species,
(5) the predator species is so exploited as a sport fish that it never becomes
abundant enough or large enough to control the targeted forage fish, and (6) the
predator is ineffective as a control agent.