Management of Introduced Fishes Chapter 13. Reasons for Fish Introductions Increase local food supplies Enhance sport & commercial fishing Manipulate

Management of Management of Introduced FishesIntroduced Fishes

Chapter 13

Reasons for Fish Reasons for Fish IntroductionsIntroductions

Increase local food suppliesIncrease local food supplies Enhance sport & commercial fishingEnhance sport & commercial fishing Manipulate aquatic systemsManipulate aquatic systems Accidents Accidents

Increase Local Food Increase Local Food SuppliesSupplies

Aquaculture Aquaculture Problems: carps, tilapiaProblems: carps, tilapia Native fishes already adapted to local Native fishes already adapted to local

conditions usually are ignoredconditions usually are ignored Nonnative fishes escape into local waterwaysNonnative fishes escape into local waterways

Enhance Sport & Enhance Sport & Commercial FishingCommercial Fishing

““Introduced fish are superior to native forms”Introduced fish are superior to native forms” Major approach to “solving” management Major approach to “solving” management

problems in North America in late-1800sproblems in North America in late-1800s Local fishes often considered unsuitable prey Local fishes often considered unsuitable prey

for the “sophisticated” anglerfor the “sophisticated” angler


Led to worldwide distribution of common carp, Led to worldwide distribution of common carp, rainbow and brown trouts, largemouth bassrainbow and brown trouts, largemouth bass

Introductions now may be “admission of defeat Introductions now may be “admission of defeat in managing native species to meet existing in managing native species to meet existing needs”needs”

Great Lakes problems (e.g., alewife)Great Lakes problems (e.g., alewife)


Alewife invades in 1880s, overabundant by 1960sAlewife invades in 1880s, overabundant by 1960s Chinook salmon stocked to control alewifeChinook salmon stocked to control alewife $4.5 billion sport fishery, plus alewife control!!!$4.5 billion sport fishery, plus alewife control!!! Chinook start reproducing, too few alewife, now Chinook start reproducing, too few alewife, now

what to do?what to do?


Introducing commercial species generally Introducing commercial species generally unsuccessful unless species is also a sport unsuccessful unless species is also a sport fish (lake trout)fish (lake trout)

Conflicts arise between user groups when Conflicts arise between user groups when demand becomes highdemand becomes high


Introducing prey species like shads, golden Introducing prey species like shads, golden shiner, smeltshiner, smelt

Accelerate growth rates of adult predatorsAccelerate growth rates of adult predators May compete directly with young predators May compete directly with young predators

for food, slowing their growth ratefor food, slowing their growth rate

Manipulate Aquatic Manipulate Aquatic SystemsSystems

Biological control of aquatic pestsBiological control of aquatic pests Mosquitoes, weeds, overabundant or stunted Mosquitoes, weeds, overabundant or stunted

preyprey Mosquitofish, grass carp, tiger muskie - Mosquitofish, grass carp, tiger muskie -

problemsproblems

Accidental IntroductionsAccidental Introductions

Bait-bucket transfersBait-bucket transfers Ballast water introductionsBallast water introductions

Ecology ofEcology ofSpecies IntroductionsSpecies Introductions

CompetitionCompetition - niche dimensions, niche - niche dimensions, niche compression, species packing, & island compression, species packing, & island biogeographybiogeography


If niches are all filled and cannot be further If niches are all filled and cannot be further compressed, introduction will fail unless compressed, introduction will fail unless introduced species is superior competitorintroduced species is superior competitor

Brown trout vs. brook troutBrown trout vs. brook trout


Disease introductionsDisease introductions - accompany introduced - accompany introduced species, and may have severe impact on native species, and may have severe impact on native speciesspecies

Whirling disease carried by exotic trout from Whirling disease carried by exotic trout from Europe have destroyed rainbow, cutthroat trout Europe have destroyed rainbow, cutthroat trout populations in Rocky Mountain riverspopulations in Rocky Mountain rivers


Disease carried by U.S. crayfish Disease carried by U.S. crayfish eliminated European crayfish from eliminated European crayfish from much of northern Europemuch of northern Europe


Predator-prey interactionsPredator-prey interactions - introduction of - introduction of predator can have dramatic, unexpected predator can have dramatic, unexpected consequences on prey communityconsequences on prey community

Introduction of Nile perch to Lake Victoria Introduction of Nile perch to Lake Victoria virtually eliminated 300 species of cichlids and virtually eliminated 300 species of cichlids and 40 species of non-cichlids40 species of non-cichlids


Indirect effectsIndirect effects - trophic cascade and habitat - trophic cascade and habitat modificationmodification

Introductions can cause complex, often Introductions can cause complex, often unpredictable effects on organisms throughout unpredictable effects on organisms throughout food web (e.g., opossum shrimp introduction led food web (e.g., opossum shrimp introduction led to increased bald eagle mortality)to increased bald eagle mortality)


Opossum shrimp intended for kokanee salmon Opossum shrimp intended for kokanee salmon and cutthroat trout in Flathead Lake, MTand cutthroat trout in Flathead Lake, MT

Competed with salmon for zooplankton --- fewer Competed with salmon for zooplankton --- fewer salmon --- fewer post-spawn salmon for bears & salmon --- fewer post-spawn salmon for bears & eagles --- eagles scavenging road-kills --- cars kill eagles --- eagles scavenging road-kills --- cars kill eagleseagles


HybridizationHybridization - introduced species - introduced species crossbreed with closely related native speciescrossbreed with closely related native species

Elimination of native cutthroat trout by Elimination of native cutthroat trout by rainbow trout in Great Basin of western U.S.rainbow trout in Great Basin of western U.S.

Alternatives to Alternatives to IntroductionsIntroductions

Use of native speciesUse of native species Better water managementBetter water management Habitat protectionHabitat protection Use of sterile fishes - triploid, single-sex Use of sterile fishes - triploid, single-sex

introductions into highly disturbed or artificial introductions into highly disturbed or artificial habitatshabitats

Evaluating Potential Evaluating Potential IntroductionsIntroductions

Guidelines (pp. 367-368) to insure Guidelines (pp. 367-368) to insure that the system and all potential that the system and all potential impacts of the introduction are impacts of the introduction are understood before the introduction understood before the introduction occursoccurs

Documents

Management of Introduced Fishes Chapter 13. Reasons for Fish Introductions Increase local food supplies Enhance sport & commercial fishing Manipulate