Fishery Biology. Fisheries Management n Provide people with a sustained, high, and ever-increasing...
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Transcript of Fishery Biology. Fisheries Management n Provide people with a sustained, high, and ever-increasing...
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– Improved access to fish– Improved effectiveness of fishing equipment– Improved processing and distribution of fish
Problems resulted in:
Overexploitation (overfishing) in many areas– Catch exceeded maximum sustainable yield
Environmental degradation Populations exhibit decline Some commercial species driven to or near
extinction
Dealing with the problem
Fish culture
Fish rescue
Fishing regulations
A progressive movement
Fish populations served:
Primary purpose - provide food
Secondary purpose - provide economic value– “crops” to be planted, managed, harvested
Maximum sustainable yield (MSY)
- efficiency
Fish population abundance changes: Additions
– Growth– Recruitment– immigration
Losses– Natural mortality– Fishing mortality– emigration
Population Dynamics
Led to conclusion that greatest long-term yield of fish achieved by allowing small fish to grow before harvesting them
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
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
Recreational Fishing Growth
Demands for regulations on competing commercial harvests
Eliminate markets for commercially caught freshwater predatory fish
Regulation of Recreational Fishing First highly restrictive, uniformly
implemented– Closed seasons, minimum size, equipment
restrictions, creel limits (daily catch) Next changed to uniformly liberal
regulations Now back to stricter regulations
Primary Funding for Inland Fishery Management in U.S. Federal Aid in Sport Fish Restoration Act
(1950)– 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)
Different Fish Problems in Different U.S. Regions Pacific NW - Pacific salmon - reduced runs
– Reduced future generations
Different Fish Problems in Different U.S. Regions SE - raising fish in farm ponds
– Predator, prey balance for best fishing
Different Fish Problems in Different U.S. Regions Midwest, Mideast - techniques for removal,
control of unwanted fishes– 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– 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
– Farm ponds– Reservoirs
MSY focus changing during last half-century More than simply maximizing physical
yield Additional concerns
– 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
– Recognizes existence of ecosystem, human need diversities
Greatly complicates management
Important additional roles of fisheries management Habitat management
– Instream flow studies– Watershed land use - mitigation– Habitat rehabilitation - streams, wetlands
Important additional roles of fisheries management Organism management
– Single-species vs. multi-species management– Endangered, rare species management– Management of non-harvested species
Prey Competitors
– Aquaculture
Important additional roles of fisheries management People management
– Methods for assessing user demands, values