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