Term
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Definition
•In the mid-1800s fishes reared and stocked into public waterways by fisheries conservation agencies.
•Stocking programs successful in establishing and supporting many fisheries, but failed to enhance the quality of others:
–They caused declines in the condition of wild fish and in the fisheries that they support.
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Term
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Definition
•Early 20th c., stocking was emphasized over all other activities: 70% of fisheries agencies budget.
•Agencies emphasized stocking in part because fisheries managers knew how to raise fish better than they understood how to regulate harvest and other human interactions with fish populations.
•Regulation of harvest by scientifically analyzing the condition of fish stocks and the impact of harvest on them did not develop until well into the 20th century.
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Term
| •Early hatchery programs focused on |
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Definition
•on introducing species into water outside of their natural geographical ranges and replenishing fish stocks depleted by harvest or habitat destruction.
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Term
•Early stocking programs were conducted with little consideration given to:
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Definition
–Conditions of the watershed
–The impact upon native fauna
-Likelihood of hatchery fish being successfully established |
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Term
| Exotic species were established in US waters before the first fish agencies were created: late 1600s, mostly : |
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Definition
•goldfish and common carp:
–Common carp occurs in all continental waters except Alaska.
–Goldfish occurs in 42 states
–Brown trout in 40 states.
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Term
| The fauna of many US waterways have been altered by introduction of exotic or North American species not native to the waterway: |
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Definition
67 species of fish have been introduced into the Colorado River
•87 species of fish have been introduced into the Great Lakes
•21 species of fish have been introduced into Florida
•19 species of fish have been introduced into California
Half the fish species in Massachusetts are introduced
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Term
–Habitat modification caused by introduced fish: Common Carp
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Definition
•uproot aquatic vegetation
•Increase turbidity
•Reduce growth rates of other fish due to turbidity.
•In late 19th c. common carp regarded as new exciting game and food fish. Today considered a major nuisance in US and of very limited value as a food source in US.
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Term
| non-native species introduction:genetic problems |
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Definition
•Introgressive hybridization
–Mating of individuals of two species closely related.
–Offspring, if fertile, reproduce with individuals of the same species of any of the two parent populations, and among themselves.
–The native gene pool is lost and this mating can disrupt the gene sequences that allow the native species to be well adapted to their environmental niche.
–Example: rainbow trout
•the introgressive hybridization of this species with other fish is so extensive that cutthroat populations are threatened.
•In golden an apache trouts the introgressive hybridization is so extensive that the hybrids are more abundant than the parent population.
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Term
•Quality of fisheries often declines quickly after they are established in reservoirs:
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Definition
–At the beginning there are good growing conditions.
–Angler catch predators such as bass
–Forage species such as sunfishes increase in population.
–Populations become stunted and produce few individuals of interest for anglers.
–The stocks of desirable species are usually maintained by annual stocking.
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Term
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Definition
•Between 1934-1965, the number of ponds increases from 20,000 to more than 2 million (overhead F.2).
•In these ponds they only stock one or a few species of fish: a combination of largemouth bass with a forage species such as bluegill.
•The buegills provide food for the bass and can sustain a panfish fisheries. They can be caught in large numbers and are considered flavorful.
After 2 or more years, predation by bass may not keep up with reproduction of sunfishes and they may reach high densities and disrupt bass reproduction |
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Term
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Definition
•Restoration involves establishing stable fish populations in waters where wild populations of the same species have been extirpated or they are endangered.
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•Restoration programs require expansive hatchery production as part of the management effort.
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Term
•situations for restoration:
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Definition
–When the population still exists, there is a gene pool still available for stocking adapted to local conditions.
–When the population has been extirpated, fisheries agencies must stock strains of fishes that are not native to the area.
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Term
| strategies for restoration |
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Definition
1.Use strains whose native environment matches the watershed to be restored.
2.Use as many strains as possible for stocking to maximize the genetic diversity introduced into the watershed.
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Term
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Definition
•Offspring do not carry the diversity of alleles characteristic of the populations being restored.
•50 – 100 fishes divided into both sexes needed to avoid inbreeding.
•Inbreeding has been exacerbated by the old practice to use the sperm from a few males to fertilize many females’ eggs.
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Term
•decisions influencing restoration include:
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Definition
what is the best size and age of of stock to introduce
when is the best time to stock
where is the best place to stock?
how many should be stocked? |
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Term
| restoration of lake trout in the great lake |
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Definition
•Control of sea lamprey: for successful reestablishment of lake trout in the GL.
•Efforts to restore lake trout in the 1950’s:
–All GL had active fisheries based on hatchery fish but almost no reproduction.
–Reasons:
•Few strains of hatchery fishes
•Inadequate number of spawners due to overexploitation and the sea lamprey.
•Reduction in egg viability due to pollutants, diseases and plant toxins
•Predation on eggs and fry
•Siltation of spawning habitats
•Stocking fish of the wrong age or at the wrong place
•Harvest level of pre-adult fishes too high.
―Minimal reproduction of lake trout in the 1990s.
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Term
| two approaches of non-reproductive stock |
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Definition
1.Fish are stocked at a “catchable” size “put-and-take” fishery ready to harvest.
2.Fish are stocked as fingerlings or fry “put-grow-and-take” fishery.
•These fisheries are often established in waters:
•unsuited for fish reproduction or
•in waters where natural reproduction cannot support the level of fishing pressure applied to the wild population.
These stocking programs focus more on meeting the recreational interests of humans than on the conservation of any natural resources.
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Term
| Pacific Salmon Fisheries in the Great Lakes |
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Definition
•Put-grow-and-take successful program
•Decades of unsuccessful attempts to introduce chinook and coho salmon into the GL.
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Term
•Fisheries on Pacific salmon established in the 1960’s due to:
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Definition
–Native lake trout populations (predator niche) severely depleted in 1960s from overfishing and invasion of sea lamprey.
–The forage base was robust due, in part, to the invasion of exotic species such as the alewife.
–Pacific salmon basically filled the void.
–Some reproduction but mostly put-grow-and-take.
–In 1990’s concern about Pacific salmon programs in the GL: decrease in survival of Pacific salmon caused in part by declining food base and possible conflict with continuing stocking Pacific salmon and restoration of lake trout.
–Questions about continuation of the put-grow-and-take fisheries.
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