1 / 19

Great Lakes Fisheries Chapter 23

Great Lakes Fisheries Chapter 23. Overfishing Problems. Sport and commercial fishing concerns Oligotrophic lakes - low productivity - low standing crop biomass of top carnivores. Overfishing. Habitat Loss/Degradation Problems. Spawning stream degradation Sedimentation Warming Dams

marrim
Download Presentation

Great Lakes Fisheries Chapter 23

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Great Lakes FisheriesChapter 23

  2. Overfishing Problems • Sport and commercial fishing concerns • Oligotrophic lakes - low productivity - low standing crop biomass of top carnivores

  3. Overfishing

  4. Habitat Loss/Degradation Problems • Spawning stream degradation • Sedimentation • Warming • Dams • Industrial/domestic pollution • Nutrient runoff • Wetlands destruction

  5. Exotic Species Problems • Sea lamprey - predation • Alewife, rainbow smelt - competition for zooplankton, predation on eggs, larvae

  6. Great Lakes System

  7. Exotic Species Problems

  8. Oligotrophy - Response to Stress • Pelagic organisms dominate • Prey species increase • Top predators decrease • Food webs simplify • Reproduction may cease • Production declines

  9. Lake Superior Changes • Lake trout and lake whitefish overfished • Sea lamprey made things worse • Lake sturgeon and ciscoes overfished • Lake herring declined from overfishing, competition with non-native rainbow smelt

  10. Lake Superior Changes • Commercial fishing restrictions: banned gill nets, quotas established, sportfishing-only zones • Sea lamprey controls: TFM, electric weirs • Stocking of lake trout, salmon • Smelt declined, whitefish rebounded, herring returned to dominance

  11. Lake Michigan Changes • Overfishing greatly reduced lake trout, lake whitefish, lake sturgeon, bigger ciscoes • Sea lamprey killed off the lake trout, further reduced lake whitefish • Alewife and smelt caused collapse of lake herring (competition and predation)

  12. Lake Michigan Changes • Alewife exploded with elimination of lake trout • Chinook and coho stocked to control alewife, once lamprey were controlled • Lake trout stocked, but little natural reproduction • Whitefish and bloater recovered after lamprey and alewife declined

  13. Lake Michigan Changes • Non-native salmon fishery worth $200 million annually • Commercial fishery for alewife (pet food) competes with salmon for prey - value? • Natural reproduction of chinook now established - interfere with lake trout recovery?

  14. Lake Erie Changes • Shallower and warmer than other Great Lakes • Same problems from overharvest, introduced species, plus pollution • Blue pike eliminated • Warmwater commercial species doing well (channel catfish, carp, shad), and walleye are increasing

  15. Alewife Management • Non-native species - pelagic feeder competes with planktivores, eats eggs of pelagic species • Out of control with lake trout collapse • Littered beaches, clogged water intakes

  16. Alewife Management • Stocking of non-native salmon to control them (30 million annually) • Alewife decline in Lake Huron so great, not enough to support salmon • Same might happen in Lake Michigan

  17. Sea Lamprey Management • 50 years of controls • TFM - $8 million per year to protect multi-billion dollar sport and commercial fisheries • Estimates of up to 90% control • But…

  18. Sea Lamprey Management • Average lamprey now twice as large as in 1970s • Ammocoete larvae may live off river mouths where treatment is not possible • TFM may lose potency, or lamprey may develop resistance to it • Controls using sterilized males, ammocoete pheromones

  19. Continuing Invasions • Ruffe in St. Louis harbor of Lake Superior - competing with yellow perch • Round goby in all lakes - compete with small, benthic fishes, but preyed on by smallmouth bass, walleye

More Related