Sea Lampreys in the Great Lakes

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Sea Lampreys in the Great Lakes

• Or,
• Lampreys Suck!

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Signs of a Fishery in Trouble

• Sharp decline in L. Michigan trout catches
• Wounds and scars appearing on larger fishes
• Live lampreys attached to their prey

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Sharp Decline in Trout Catches
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Fresh wounds on whitefish
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Healed scars on larger fish
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Live lampreys and wounds on lake trout
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Multiple wounds on larger fish
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Evidence that Sea Lampreys were the Problem

• Increase in numbers of lampreys caught in the
  fisheries
• Only the larger fishes were affected

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Progressive collapse of fisheries in order of
proximity to Niagara Falls
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Possible Migration Routes to Upper Great Lakes

• Earliest access above Niagara Falls was via the
  New York State Barge Canal (Erie Canal)
• In 1935 the Welland Canal was expanded to
  increase the capacity of Great Lakes shipping

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Access to Upper Lakes
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Immediate Management Actions

• Formed the GLFC by treaty between the U.S. and
  Canada
• Began studying the life history of sea lamprey
• Started to control adult lampreys by physical and
  mechanical barriers on spawning tributaries to
  the Great Lakes
• Established research laboratories on Great Lakes
  fisheries in the U. S. and Canada

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Hammond Bay Laboratory
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Key Features of Life History

• Adults migrate upstream to spawn on gravel
  substrate, then die after spawning
• Juveniles hatch and live in streams as ammocoetes
  (larval lampreys) filter-feeding until they are
  approximately 120mm in length
• Ammocoetes transform into predatory (or,
  parasitic) forms and migrate downstream into the
  lakes
• Feeding takes place on fish for period of 12-18
  months
• Maturing adults migrate back up tributary streams
  for spawning

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Sea Lampreys Ready to Spawn
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Massive stream surveys were undertaken to
identify lamprey habitat

• Every tributary to the upper Great Lakes was
  searched for presence of juvenile sea lampreys
• Electrofishing was the favored sampling method

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Earliest control methods were mechanical and
electrical weirs and traps
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Trap-caught sea lampreys
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Chemical Larvicide Discovered in 1958

• TFM (3-trifluoromethyl-4-nitrophenol) a chemical
  used in the carpet dyeing industry, was found to
  be selectively toxic to juvenile lampreys

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Chemical metered into ammocoete streams to kill
larvae

• TFM is effective in killing lamprey larvae (all
  species) at concentrations of about 2 ppm. It
  also kills certain mayfly and stonefly larvae at
  these concentrations. It is lethal to most other
  fishes at levels above 4 ppm, and administration
  of the chemical is a highly demanding procedure,
  fraught with uncertainties such as poor mixing
  and dilution due to thunderstorms and spring
  seepage.

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Cumulative Impact of Treatment Catches Several
Year-classes at Once
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Chemical Control Must be Maintained
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Larger and most economically valuable fishes
remain vulnerable to sea lamprey predation
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Limitations on TFM control

• Some streams are virtually untreatable, e.g. the
  St. Marys River between L. Superior and Lake
  Huron
• Environmental costs (especially to invertebrates)
• Single supplier for the compound (until recently)
• Expensive to administer

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Alternative Control Measures

• Barrier dams
• Combinations with other chemicals (Bayer 73)
• Electrical weirs and traps
• Sterile male controls

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Hope for Future Control

• After 16 years of research, Dr. P. Sorensen at U
  of Minnesota discovers pheromone effective in
  attracting mature lampreys
• The compound is related to bile acids excreted by
  ammocoetes in streams suitable for lamprey
  production
• The new approach promises to provide a method for
  luring wild lampreys to sites suitable for
  trapping