great lakes fisheries chapter 23. overfishing problems sport and commercial fishing concerns...
Post on 14-Dec-2015
214 Views
Preview:
TRANSCRIPT
Great Lakes FisheriesGreat Lakes FisheriesChapter 23Chapter 23
Overfishing ProblemsOverfishing Problems
Sport and Sport and commercial fishing commercial fishing concernsconcerns
Oligotrophic lakes Oligotrophic lakes - low productivity - - low productivity - low standing crop low standing crop biomass of top biomass of top carnivorescarnivores
OverfishingOverfishing
Habitat Habitat Loss/Degradation Loss/Degradation
ProblemsProblems Spawning stream Spawning stream
degradationdegradation SedimentationSedimentation WarmingWarming DamsDams
Industrial/domestic Industrial/domestic pollutionpollution
Nutrient runoffNutrient runoff Wetlands Wetlands
destructiondestruction
Exotic Species ProblemsExotic Species Problems
Sea lamprey - Sea lamprey - predationpredation
Alewife, rainbow Alewife, rainbow smelt - competition smelt - competition for zooplankton, for zooplankton, predation on eggs, predation on eggs, larvaelarvae
Great Lakes SystemGreat Lakes System
Exotic Species ProblemsExotic Species Problems
Oligotrophy - Response Oligotrophy - Response to Stressto Stress
Pelagic organisms Pelagic organisms dominatedominate
Prey species Prey species increaseincrease
Top predators Top predators decreasedecrease
Food webs simplifyFood webs simplify Reproduction may Reproduction may
ceasecease Production declinesProduction declines
Lake Superior ChangesLake Superior Changes Lake trout and lake Lake trout and lake
whitefish overfishedwhitefish overfished Sea lamprey made Sea lamprey made
things worsethings worse Lake sturgeon and Lake sturgeon and
ciscoes overfishedciscoes overfished Lake herring declined Lake herring declined
from overfishing, from overfishing, competition with non-competition with non-native rainbow smeltnative rainbow smelt
Lake Superior ChangesLake Superior Changes Commercial fishing Commercial fishing
restrictions: banned gill restrictions: banned gill nets, quotas established, nets, quotas established, sportfishing-only zonessportfishing-only zones
Sea lamprey controls: Sea lamprey controls: TFM, electric weirsTFM, electric weirs
Stocking of lake trout, Stocking of lake trout, salmonsalmon
Smelt declined, Smelt declined, whitefish rebounded, whitefish rebounded, herring returned to herring returned to dominancedominance
Lake Michigan ChangesLake Michigan Changes Overfishing greatly Overfishing greatly
reduced lake trout, reduced lake trout, lake whitefish, lake lake whitefish, lake sturgeon, bigger sturgeon, bigger ciscoesciscoes
Sea lamprey killed off Sea lamprey killed off the lake trout, further the lake trout, further reduced lake whitefishreduced lake whitefish
Alewife and smelt Alewife and smelt caused collapse of lake caused collapse of lake herring (competition herring (competition and predation)and predation)
Lake Michigan ChangesLake Michigan Changes Alewife exploded with Alewife exploded with
elimination of lake troutelimination of lake trout Chinook and coho Chinook and coho
stocked to control stocked to control alewife, once lamprey alewife, once lamprey were controlledwere controlled
Lake trout stocked, but Lake trout stocked, but little natural little natural reproductionreproduction
Whitefish and bloater Whitefish and bloater recovered after lamprey recovered after lamprey and alewife declinedand alewife declined
Lake Michigan ChangesLake Michigan Changes Non-native salmon Non-native salmon
fishery worth $200 fishery worth $200 million annuallymillion annually
Commercial fishery Commercial fishery for alewife (pet food) for alewife (pet food) competes with salmon competes with salmon for prey - value?for prey - value?
Natural reproduction Natural reproduction of chinook now of chinook now established - interfere established - interfere with lake trout with lake trout recovery?recovery?
Lake Erie ChangesLake Erie Changes Shallower and warmer Shallower and warmer
than other Great Lakesthan other Great Lakes Same problems from Same problems from
overharvest, introduced overharvest, introduced species, plus pollutionspecies, plus pollution
Blue pike eliminatedBlue pike eliminated Warmwater commercial Warmwater commercial
species doing well species doing well (channel catfish, carp, (channel catfish, carp, shad), and walleye are shad), and walleye are increasingincreasing
Alewife ManagementAlewife Management
Non-native species - pelagic feeder competes Non-native species - pelagic feeder competes with planktivores, eats eggs of pelagic specieswith planktivores, eats eggs of pelagic species
Out of control with lake trout collapseOut of control with lake trout collapse Littered beaches, clogged water intakesLittered beaches, clogged water intakes
Alewife ManagementAlewife Management
Stocking of non-native salmon to control them Stocking of non-native salmon to control them (30 million annually)(30 million annually)
Alewife decline in Lake Huron so great, not Alewife decline in Lake Huron so great, not enough to support salmonenough to support salmon
Same might happen in Lake MichiganSame might happen in Lake Michigan
Sea Lamprey Sea Lamprey ManagementManagement
50 years of controls50 years of controls TFM - $8 million per year to protect multi-billion TFM - $8 million per year to protect multi-billion
dollar sport and commercial fisheriesdollar sport and commercial fisheries Estimates of up to 90% controlEstimates of up to 90% control But…But…
Sea Lamprey Sea Lamprey ManagementManagement
Average lamprey now twice as large as in 1970sAverage lamprey now twice as large as in 1970s Ammocoete larvae may live off river mouths where Ammocoete larvae may live off river mouths where
treatment is not possibletreatment is not possible TFM may lose potency, or lamprey may develop TFM may lose potency, or lamprey may develop
resistance to itresistance to it Controls using sterilized males, ammocoete pheromonesControls using sterilized males, ammocoete pheromones
Continuing InvasionsContinuing Invasions RuffeRuffe in St. Louis in St. Louis
harbor of Lake harbor of Lake Superior - Superior - competing with competing with yellow perchyellow perch
Round gobyRound goby in all in all lakes - compete lakes - compete with small, benthic with small, benthic fishes, but preyed fishes, but preyed on by smallmouth on by smallmouth bass, walleyebass, walleye
top related