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Understanding Fish Management |
Fisheries management is the science of manipulating fish
populations within a body of water in order to achieve maximum desirable production.
Maintaining these populations requires that the species present must survive, grow
and reproduce. The typical objectives for managing fish are for food and/or
recreational resources.
Of primary concern is providing a suitable environment to meet the needs of the fish
species' habitat and food requirements. Acceptable water quality is extremely important.
Most of these parameters and requirements are discussed in the sections covered under
"Understanding Water Quality".
| Warm Water | Cool Water | Cold Water |
Largemouth bass
Striped bass
Sunfish (bream)
Crappie
Catfish |
Walleye
Smallmouth bass
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Yellow perch
Trout
Salmon |
Most warm water species will do well within a wide range of water temperatures from ice-covered waters
to beyond 800F, although growth will be slower in cooler water. Cool water fish prefer temperatures ranging
into the upper 60's (F0). Cold water varieties are best suited for temperatures below 650F. Within ponds or
lakes, which thermally stratify, species from several of these groups may do well.
Other important considerations include providing hiding places for young fish and suitable substrate for
spawning. These requirements vary widely with species, therefore, knowing the life history of each is important.
Controlling aquatic plants to acceptable levels, as discussed in the first part of this book, is of primary concern
in limiting cover. Too much vegetation will lead to an overabundance of small, stunted fish. Proper bottom materials
(sand, gravel, etc.) or plant stems may be required for depositing eggs. In some bodies of water, cover or bottom
materials may have to be provided. Structures, called "cribs", consisting of rock piles, fallen trees, or bundles
of branches are sunk into the water for this purpose. Artificially constructed reefs and gravel bars may also be
installed.
Decisions to stock fish must be based upon the conditions of the existing habitat and particularly take into
account what fish are already present. Any given body of water will have a certain carrying capacity or
maximum production. Simply adding fish to an existing population is rarely successful, unless there is an
excess of food and unoccupied habitats. Suitable numbers of forage (food) fish must be present if larger
predator fish are to survive. Choice of species and stocking ratios will vary geographically and by environmental
conditions. Therefore, contacting the biologists at local fisheries or hatchery operators is recommended.
Some may be able to provide a fisheries management survey to determine the existing balance and condition of the
population.
Avoid the mistake of expecting to control a stunted panfish population by simply adding a number of large predators.
(Hybrid or non-reproducing sunfish have become a popular alternative to avoid problems with overpopulation of stunted
panfish). Similarly, do not assume that a gamefish population can be established within a body of water overrun with
carp or rough fish. Either of these situations should be remedied with an eradication program of existing fish stocks.
This can be done through draining or use of a fish toxicant such as Rotenone. If fish are stocked, obtain them from a
reputable hatchery. Make certain that they are free of disease and healthy upon their arrival. Handle them carefully
and as little as possible. The temperature difference between the holding water and the lake or pond should not exceed
100F. If it is, fish must be gradually acclimated.
The amount of fishing pressure required to sustain a balanced population will vary. Panfish can usually be caught when
they reach desired size. Intensive removal of panfish may be required to avoid stunting problems. Similarly, size and
catch limits might be imposed upon larger fish to ensure their numbers. However, it is best not to remove predator gamefish
until after they spawn (approximately 3 years after stocking).
Except under exceptionally sterile conditions or where extremely high productivity is desired (such as aquaculture ponds),
fertilization and feeding programs are not recommended. Properly managed waters contain enough fertility to support good
fish growth. Addition of more nutrients may only lead to undesirable and uncontrolled weed and algae growth.
Keep records of fish stocking and a creel census of what has been caught. Examine fish periodically for signs of stress
or disease. Check water quality regularly for signs of trouble. Consult an expert if problems are suspected.
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