Lecture 2'6 Stocking and Removing Fish and Wildlife

1
Lecture 2.6Stocking and RemovingFish and
Wildlife

• Natural Resources 250
• Michael J. Hansen
• Professor of Fisheries

2
Outline

• Introduction
• Population removals.
• Partial population removals.
• Complete population removals.
• Stocking.
• New introductions.
• Maintenance stocking.
• Enhancement stocking.

3
(No Transcript)
4
Population Removals

• Intended to remove undesirable species.
• Integrated pest management.
• Chemical control methods.
• Biological control methods.
• Mechanical control methods.

5
Population RemovalsChemical Control Methods

• Fish toxicants.
• Should be specific for target species.
• Should be biodegradable.
• Should be safe for humans.
• Should be lethal over wide range of conditions.

6
Population RemovalsChemical Control Methods

• Rotenone and antimycin are for general use.
• Toxicity is related to water conditions.
• Temperature.
• Alkalinity.
• Sunlight.
• Fish species vary in their susceptibility.
• Use high concentration to achieve total kill.

7
Population RemovalsChemical Control Methods

• TFM and Bayer-73 are for sea lampreys.
• Toxicity is related to water conditions.
• Temperature (freezing reduces toxicity).
• pH (toxicity drops above pH above 8.0).
• Toxic to all lampreys, insects, and some fish.
• Optimize concentration to kill only lampreys.

8
Population RemovalsChemical Control Methods

• Benefits should exceed costs.
• Benefits are rarely quantified (too difficult).
• Costs are often very high.
• Effectiveness is related to longevity.

9
Population Removals Biological Control Methods

• Stocking may seek biological control.
• Stock predators to control prey species.
• Stock prey species to increase predator growth.

10
Population Removals Biological Control Methods

• Parasites and pathogens.
• Risky because effects are unpredictable.
• Native species may be affected.

11
Population Removals Biological Control Methods

• Sterile-male releases.
• Sterilization method has high RD costs.
• Sterilization facility has high construction
  cost.
• Sterilized individuals are released.
• Mating produces nonviable eggs.
• Several generations eliminate target species.

12
Population Removals Mechanical Control Methods

• Water level manipulation.
• Barriers to migration.
• Traps and nets for fish.
• Guns or traps for birds or mammals.

13
StockingOldest Fishery Management Practice

• Fishing often depleted local fish stocks.
• Depleted stocks were often re-stocked.
• Natural stocks were often supplemented.
• Widespread stocking was later questioned.
• Stocking is still widely practiced.
• Stocking is still viewed as panacea.

14
StockingNew Introductions

• Risk is related to distance of transfer.
• Intercontinental transfer.
• Intra-continental transfer.
• Intra-regional transfer.

15
StockingNew Introductions

• Risk is related to degree of system closure.
• Degree to which systems are connected.
• Degree of public access.
• Birds and mammals may still transfer species.

16
StockingNew Introductions

• Risk is related to system perturbation.
• Native species assemblages.
• Non-native species assemblages.
• New reservoirs.

17
StockingNew Introductions

• Risk is related to parasites and pathogens.
• Parasites and pathogens co-evolve with species.
• Presences is often overlooked (not obvious).
• Species must be quarantined.

18
StockingNew Introductions

• Risk is related to likelihood of spreading.
• Introduced species may reproduce and spread.
• Introduced species should be sterilized.
• Sterilization may not be 100 effective.

19
StockingRe-Introductions

• System reclamation.
• Removal of all desirable species possible.
• Eradication of all remaining species.
• Re-introduction of desirable species.

20
StockingRe-Introductions

• Native species restoration (not endangered).
• Habitat degradation may eliminate species.
• Overexploitation may eliminate species.

21
StockingRe-Introductions

• Endangered species restoration.
• Identify causes of endangerment.
• Habitat destruction.
• Interactions with non-native species.
• Overexploitation by humans.
• Recovery plan identifies remedies to problems.
• Acquire or protect critical habitat.
• Eliminate deleterious non-native species.
• Reduce human exploitation.

22
StockingMaintenance Stocking

• Put-and-take stocking.
• Conditions unsuitable for year-round survival.
• Annual stocking needed to maintain species.

23
StockingMaintenance Stocking

• Put-grow-and-take stocking.
• Conditions suitable for survival.
• Conditions unsuitable for reproduction.
• Spawning gravel for trout (coldwater streams).
• Spawning streams for striped bass (reservoirs).
• Spawning shoals for walleye (natural lakes).

24
StockingEnhancement Stocking

• Supplement self-sustaining populations.
• Abundance may be naturally low.
• Manager wishes to supplement stock.
• Supplemented population may provide more benefits
  to humans than original population.

25
StockingEnhancement Stocking

• Inadequate spawning habitat.
• Spawning may limit number of individuals.
• Exploitation must be limited.
• Stocking may provide more harvest.

26
StockingEnhancement Stocking

• Growth over-fishing.
• Loss of large, fast-growing individuals.
• Small, slow-growing individuals survive.
• Stocking introduces more individuals.
• Growth may improve, if below carrying capacity.
• However, supplementation rarely works.

27
StockingEnhancement Stocking

• Recruitment over-fishing.
• Loss of adults, so recruitment declines.
• Stock declines to commercial extinction.
• Stocking introduces more individuals.
• Recruitment may improve, if stocked fish
  reproduce.
• However, supplementation rarely works.

28
StockingEnhancement Stocking

• Mixed stock over-fishing.
• Stocked fish often outnumber wild fish.
• If true, wild fish are driven to extinction.
• Must limit exploitation to level that is
  sustainable for wild component of mixed stock.

29
StockingFactors Influencing Success

• Size and condition of stocked individuals.
• Number released.
• Conditions at time of stocking.
• Suitability of environmental conditions.
• Availability of food.
• Availability of cover from predators.
• Difficult to ensure success!