Download Fishery Biology

Fishery Biology
Fisheries Management
Provide people with a sustained, high, and
ever-increasing benefit from their use of
aquatic resources
 Problems - late-1800s - industrial revolution
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Improved access to fish
Improved effectiveness of fishing equipment
Improved processing and distribution of fish
Problems resulted in:

Overexploitation (overfishing) in many
areas
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Catch exceeded maximum sustainable yield
Environmental degradation
 Populations exhibit decline
 Some commercial species driven to or near
extinction
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Dealing with the problem
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Fish culture
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Fish rescue
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Fishing regulations
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A progressive movement
Fish populations served:
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Primary purpose - provide food
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Secondary purpose - provide economic value
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“crops” to be planted, managed, harvested
Maximum sustainable yield (MSY)
- efficiency
Fish population abundance
changes:
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Additions
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Growth
Recruitment
immigration
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Losses
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Natural mortality
Fishing mortality
emigration
Population Dynamics
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Led to conclusion that greatest long-term
yield of fish achieved by allowing small fish
to grow before harvesting them
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But no scientific proof!
Ecology and Fisheries

Ecology as a science provided hypotheses,
principles, and fisheries provided natural
laboratories for testing them
Early Focus of Fisheries Science
Describe, survey fish, etc., in important
waters
 Determine physicochemical characteristics
 Gather fish life history, ecology information
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New Data
Confirmed that habitat destruction,
overfishing had negative impacts on fish
populations
 Led to growth of fisheries management,
development of most techniques still used
today
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Recreational Fishing Growth
Demands for regulations on competing
commercial harvests
 Eliminate markets for commercially caught
freshwater predatory fish
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Regulation of Recreational
Fishing
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First highly restrictive, uniformly
implemented
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Closed seasons, minimum size, equipment
restrictions, creel limits (daily catch)
Next changed to uniformly liberal
regulations
 Now back to stricter regulations
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Primary Funding for Inland
Fishery Management in U.S.

Federal Aid in Sport Fish Restoration Act
(1950)
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Dingell-Johnson (D-J) Act
10% excise tax on specified fishing equipment
Primary Funding for Inland
Fishery Management in U.S.
Wallop-Breaux Act (1985)
 Expanded range of items taxed (e.g., boat
fuel)
 Extended funding to marine recreational
fisheries
 Doubled previous level of funding ($332
million in 1992)
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Different Fish Problems in
Different U.S. Regions

Pacific NW - Pacific salmon - reduced runs
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Reduced future generations
Different Fish Problems in
Different U.S. Regions

SE - raising fish in farm ponds
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Predator, prey balance for best fishing
Different Fish Problems in
Different U.S. Regions

Midwest, Mideast - techniques for removal,
control of unwanted fishes
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Commercial netting
Chemical fish poisons
Fish Stocking Changes
Initially widespread, promiscuous
introductions of fish eggs, larvae
 Now more selective stocking, where growth
and survival are probable
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Raised in hatcheries to larger size for better
survival
“put-and-take” stocking of catchable-size fish
Habitat Modifications
Habitat-related limits to fish size,
abundance
 Improve habitat to remove limits
 Add artificial structures to lakes, streams
 Build artificial lakes
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Farm ponds
Reservoirs
MSY focus changing during last
half-century
More than simply maximizing physical
yield
 Additional concerns
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Economic - e.g., aesthetic values
Sociological - e.g., limited access to fishery
Ecological - e.g., multi-species management
Optimum Sustainable Yield
Includes broad range of concerns
 Unique management goal for each fishery
 More realistic
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Recognizes existence of ecosystem, human
need diversities
Greatly complicates management
Important additional roles of
fisheries management
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Habitat management
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Instream flow studies
Watershed land use - mitigation
Habitat rehabilitation - streams, wetlands
Important additional roles of
fisheries management
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Organism management
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Single-species vs. multi-species management
Endangered, rare species management
Management of non-harvested species
 Prey
 Competitors
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Aquaculture
Important additional roles of
fisheries management
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People management
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Methods for assessing user demands, values