Minutes of the
Lake Superior Technical Committee Meeting
Ojibwa Motel
Baraga, MI
August 6-8, 1996
Part II
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Agenda Item 7 - Isle Royale Lake Trout Assessment
Mike Donofrio requested that the LSTC discuss the information available on lake trout stocks in MI-1, and committee evaluate the need for a spring gill net survey in the area. Chuck Bronte indicated Gary Curtis of the NBS has had a manuscript accepted by the Transactions of the American Fisheries Society that focuses on lean lake trout populations at Isle Royale. The manuscript describes catches of lake trout made by commercial assessment fisheries around the island during 1958-1990. Gary has not submitted a revised draft of the manuscript to the TAFS. Chuck Bronte reported that the Curtis manuscript has figures illustrating that harvest and CPUE were stable from 1929 to the 1950s, declined from the 1950's through the late 1960s, then increased again to levels greater than during the 1929-50 time period.
The MDNR currently issues two permits for fishing lake trout with gill nets in the Isle Royale Park during June through September. One permit belong to Sivertson and allows a harvest of 600 lake trout. Siverton provides length, weights, fin clips, lamprey wounding, and scale samples from the harvested fish. The other permit is given to the Park Service and has a quota of 400 fish. The Park Service uses the permit as a demonstration of what commercial fisheries used to be like on the island. The demonstratin fisher collects the basic fishery data along with otoliths. The MiDNR began collectiong data from the permit fisheries in 1990 and the data covers June to September. For the demonstration fishery, CPUE averaged 15-16 wild fish/1000 ft. of net in one night sets, with 97% of the fish being wild. Fish of ò25 inches long made up 50-57% of the catch during 1990-95. Sea lamprey wounding rates are low averaging less than 5 marks/100 fish.
The Ashland NBS office has also collected data on lake trout from around Isle Royale. In 1990, NBS set 4 1/2 inch gill nets all around the island to target lean lake trout in June. Nothing has been done with the data since it was collected in 1990. NBS collected over 900 fish during the survey by setting and lifting 4 short gangs every day during a eight day period.
Mike Donofrio submitted a proposal to the Park Service to conduct a spring survey of lean lake trout at MI-1 in 1996, but the proposal was denied by the Park Service. Mike proposed to harvest only 400 fish at two sites. The LSTC agreed that there is a need for collection of biological data from lake trout around Isle Royale, but that the survey may not need to be conducted every year. The LSTC will stress to the Park Service that the data will be collected only for scientific purposes. MiDNR will continue to collect the data from the permit fishery. Jim Peck indicated that Michigan may also be willing to include in the permit that Sivertson collect otoliths, with assistance from John Johnson of the Grand Portage Band.
Action Item - Chuck Bronte will work up the NBS data collected in 1990 from around Isle Royale, and compare it to data collected from other areas of Lake Suprior in the same year. Mark Ebener will talk to Gary Curtis about finishing the Isle Royale manuscript, and Ebener will relay to the Park Service that the LSTC has identified a need for a spring survey of lean trout in the Isle Royale area. Jim Peck will provide the LSTC with a summary of data collected from the permit fishery around Isle Royle from 1990-95.
Agenda Item 8 - Minnesota Size at Stocking Experiment
Don Schreiner distributed a handout summarizing the experiment MnDNR is currently conducting to evaluate survival of lake trout initially stocked at different sizes. For fish caught 1 1/2 months after stocking with a trawl, survival of lake trout of 12-13 fish/lb was nearly twice that for fish of 32/lb. The larger-sized fish at stocking seemed to move greater distances than smaller fish. It also appeared that the larger the fish the better the survival, and that fish stocked from the Iron River National Fish Hatchery survived better than fish transported from the MnDNR Crystal Spring Hatchery even when the lake trout were the same size. Lake trout given three fin-clips before stocking appeared to experience lower survival than other fish stocked as part of the experiment.
Agenda Item 9 - Net Saturation
Mike Hansen provided a handout to the LSTC that described his progress at examining the increase in lake trout CPUE that results from increased numbers of days that gill nets were set. In 1995, The MiDNR set and lifted different gangs of gill nets set for one to five nights at six different sites in MI-3 and MI-4. Mike's analysis up to this point suggested that a nonlinear model that assumes one slope in all areas and different asymptotes showed the best fit to the data. Mike has tentatively agreed to present the results of his work at the winter meeting of the LSTC.
Agenda Item 10 - Lake Trout Stocking
a. Stocking and brood stocks - The USFWS stocked just over 500,000 fish into Lake Superior in 1996. These fish ranged in size from 8-13/lb. The USFWS plans to gather more gametes from wild stocks at Gull Island and Traverse Island as backups for broodstock. These fish will be housed at the new isolation facility in Genoa, WI. Dale Bast indicated that the USFWS will be reducing the size of the present brood stock in order to pare down the size of the brood stock to match egg needs. The reduction in number of brood stock will result in 4 million less eggs being collected 1996. The reduction in brood stock will likely not reduce total egg production because new brookstocks that are now just maturing will produce more eggs in the future.
b. Fin clips - The LSTC has shown an interest in modifying the current fin clip schedule for Lake Superior. We would like to reserve the adipose fin for coded-wire tag studies, not use double clips, and replace the adipose clip with the dorsal clip in the fin clip rotation. No final decision was made on this proposal.
c. Isolation facility update - The lots of humpers, Gull Island and Traverse Island lean trout, and coaster brook trout being held at the Keweenaw Bay isolation facility had been certified as disease free thus far. Mike Donofrio indicated that he will be stocking excess Traverse Island and Gull Island fish from his isolation facility into lower Keweenaw Bay this fall to thin down the number of fish he will carry through the winter.
Agenda Item 11 - Orienta Dam Passage
Stephen Schram and Dale Bast outlined the issues and presented the current status of the Orienta Dam on the Iron River in Wisconsin. The Orienta dam on the Iron River washed out due to flooding in 1985 or 1986. WDNR has been working with the power company to decide the final fate of the dam. Right now they are draining the flowage and the dam will be removed in 1997, but part of the dam will remain in place to serve as a sea lamprey barrier that will not allow passage of anadromous fish. The USFWS and WDNR are currently negotiating an agreement to place another dam upstream on the Iron River near the federal hatchery. In the year 2001, the WNDR is tentatively planning on placing a fish ladder at the Orienta dam sea lamprey barrier to pass anadromous stocks from Lake Superior into the Iron River. Construction of the fish ladder and placement of a barrier further upstream are continguent upon funding, that at the current time is not forthcoming.
The LSTC is concerned about two issues related to the Orienta Dam. First, removal of the dam should not allow passage of sea lamprey into the river system. Second, passage of anadromous fish upstream of the dam should not expose the Iron River lake trout to disease, particularly BKD. Fish resident to the tributaries of the Iron River have been tested for disease, but only one fish tested positive for BKD. In comparison, all fish collected from the Brule River tested positive for BKD and some other diseases. The MiDNR Marquette hatchery and the USFWS Pendills Creek hatchery both have barriers to prevent andromous fishes from entering each hatchery complex, and these barriers are located in close proximity to the hatchery.
Agenda Item 12 - Lake Trout Model Update
Chris Weeks of MSU provided a summary to the LSTC of the work Dr. Jim Bence and he are conducting to model lake trout stocks in Lake Superior. The LSTC recognized the need to have Dr. Bence and Chris Weeks attend the winter meeting to summarize their work.
Agenda Item 13 - Acoustics Schedule
Tim Johnson and Doran Mason provided the LSTC with a cruise schedule for the acoustics assessment of prey stocks in the western basin of Lake Superior that is to be conducted in August 1996. The survey will target smelt, chubs, and herring, and nothing else. This project is just a preliminary program to begin applying acoustics work to Lake Superior, therefore, the survey is not scheduled to be repeated in 1997.
Agenda Item 14 - Catch and Mortality of Loons in Trap Nets
Jim Peck provided the LSTC with a brief summary of a study MiDNR and Northern Michigan University are conducting to reduce the mortality of common loons caught in commercial trap nets. Initital results of the study indicate that placing larger mesh sizes in the hearts can substantially reduced mortality of the loons that swim into the nets. Jim Peck will provide a summary of the study at the winter meeting of the LSTC.
Agenda Item 15 - Time and Place of Winter Meeting
The place is Ashland and the date is January 28-30, 1997. Chuck Bronte will take care of the meeting arrangements.
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