Integrated Management of Sea Lampreys in the Great Lakes
1996 Annual Report to the Great Lakes Fishery Commission


ASSESSMENT

Larval

Tributaries of the Great Lakes systematically are assessed for abundance of sea lamprey larvae (quantitative surveys) and distribution (qualitative surveys) to determine when and where lampricide treatments are required and effectiveness of past treatments. Surveys primarily are conducted with backpack electrofishers in waters <1 m deep. Waters of >1 m depth are surveyed with deepwater electrofishers or the granular formulation of Bayluscide. Data collected from these surveys are used to estimate the numbers of transforming larvae that will leave individual tributaries the following year and to recommend where lampricides should be applied.

Streams considered candidates for lampricide treatment in 1997 were surveyed in 1996 to provide statistically reliable estimates (+/- 50 percent of the mean) of larval densities and amounts of habitable substrates. Survey plots randomly were selected in each stream, catches of larvae corrected for gear efficiency, and lengths of larvae standardized to the end of the growing season. Populations of larvae were estimated by multiplying the mean density of larvae in the plots by the estimated total habitat suitable to larvae in the tributary. A curve for probability of transformation derived from historical data was used to estimate the number of larvae that would transform and leave the stream in 1997. The streams scheduled for treatment in 1997 were ranked on an estimated cost per kill of transformers.

The Assessment Task Force was established in 1996 to develop an optimal assessment program through the review of established protocols and the development of new techniques for assessment in the Sea Lamprey Control Program. The report on progress is presented on pages 70 and 71.

Lake Superior


Table 9. Status of Lake Superior tributaries that have been treated for sea lamprey larvae, 1987-1996.


Lake Michigan


Table 10. Status of tributaries of Lake Michigan that have been treated for sea lamprey larvae, 1987-1996.


Lake Huron


Table 11. Status of tributaries of Lake Huron that currently support larval sea lamprey populations and/or have been treated for sea lamprey larvae, 1987-1996.


Lake Erie


Table 12. Status of tributaries of Lake Erie that have been treated for sea lamprey larvae, 1987-96.


Lake Ontario


Table 13 . Status of tributaries of Lake Ontario that have been treated for sea lamprey larvae, 1987-96.


Spawning-Phase

Mechanical traps are used to monitor spawning migrations of sea lampreys in spring and early summer. Traps are either portable (rectangular steel mesh, hoop, or fyke nets) or permanent (generally concrete) and usually are associated with a physical or electrical barrier. Trap catch of sea lampreys is a measure of relative abundance.

Stratified multiple mark/recapture studies are conducted in most streams to estimate the spawning population for the year. Lake estimates are computed based on a regression relation (y=ax) where a is the slope of the regression, x is the average stream discharge, and y is the estimated number of adult lampreys that enter tributaries. Biological characteristics (sex, length, weight) are recorded from lampreys removed from each river.

Lake Superior


Table 14. Stream, number, estimate population, trap efficiency and biological characteristics of adult sea lampreys captured in assessment traps in tributaries of Lake Superior, 1996. (Number in parentheses corresponds to location of stream in figure 9.)


Fig. 9. Location of streams where assessment traps were operated in 1996.
Table 15. Spring mean discharge for U.S. streams east and west of Keweenaw Peninsula (Lake Superior) from April 1 to June 30, 1996, ranked as primary1 and secondary2 producers of sea lampreys, and the estimated number of spawning-phase sea lampreys.

Lake Michigan


Table 16. Stream, number, estimated population, trap efficiency and biological characteristics of adult sea lampreys captured in assessment traps in tributaries of Lake Michigan, 1996. (Number in parentheses corresponds to location of stream in Fig. 9.)


Table 17. Spring mean discharge for U.S. streams in Lake Michigan, from April 1 to June 30, 1996, ranked as primary1 and secondary2 producers of sea lampreys, and the estimated number of spawning-phase sea lampreys. Streams are grouped west of a line between the Manistique and Betsie rivers, and east (inclusive).


Lake Huron

Lake Erie

Lake Ontario


Table 18. Stream, number, estimated population, trap efficiency, and biological characteristics of adult sea lampreys captured in assessment traps in tributaries of Lake Huron, 1996. (Number in parentheses corresponds to location of stream in Fig. 9).


Table 19. Annual mean discharge for U.S. and Canadian streams north and south of a line from Alpena, Michigan to Espanola, Ontario in Lake Huron, ranked as primary1 and secondary2 producers of sea lampreys, and the estimated number of spawning-phase sea lampreys in 1996.


Table 20. Stream, number, estimated population, trap efficiency, and biological characteristics of adult sea lampreys captured in assessment traps in tributaries of Lake Erie, 1996. (Number in parentheses corresponds to location of stream in Fig. 9).


Table 21. Stream, number, estimated population, trap efficiency, and biological characteristics of adult sea lampreys captured in assessment traps in tributaries of Lake Ontario, 1996. (Number in parentheses corresponds to location of stream in Fig. 9)


Table 22. Annual mean discharge for streams in Lake Ontario and the estimated number of spawning-phase sea lampreys in 1996.


Parasitic-Phase

Lake Superior

The Michigan Department of Natural Resources provided data on the frequency of parasitic-phase sea lampreys attached to fish caught by sport charterboats.

Lake Michigan

The Michigan and Wisconsin Departments of Natural Resources provided data on the frequency of parasitic-phase sea lampreys attached to fish caught by sport charterboats.

Lake Huron

The Michigan Department of Natural Resources provided data on the frequency of parasitic-phase sea lampreys attached to fish caught by sport charterboats. Personnel from the Lake Huron Biological Station and Sea Lamprey Control Centre collected parasitic-phase sea lampreys from eight commercial fisheries.



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