This report summarizes activities in the integrated management of sea lampreys conducted by the U.S. Fish and Wildlife Service and the Department of Fisheries and Oceans Canada in the Great Lakes in 1996. Lampricide treatments were conducted on 57 tributaries (Table 1). Larval assessment crews surveyed 223 Great Lakes tributaries, inland lakes, and lentic areas to assess TFM treatment or barrier effectiveness, plan future TFM treatments, and establish production capacity of streams. Assessment traps were operated in 63 tributaries to estimate the spawning-phase population in each lake (Table 2).
The fish community objective for the sea lamprey population in Lake Ontario, set by the Lake Committee, is being met. The uncontrolled population of sea lamprey larvae in the St. Marys River continues to produce an unacceptably high population of parasitic lampreys in Lake Huron that are compromising lake trout rehabilitation in that lake. In addition, parasitic sea lampreys are more abundant in the northern part of Lake Michigan than in the south and likely are a threat to lake trout survival in the rehabilitation refuges and zones. Wounding rates on lake trout in Lake Erie have edged slightly above the target level of five percent.
Further progress was achieved in development of an effective strategy to control sea lampreys in the St. Marys River. Mapping of the distribution and density of sea lamprey larvae was completed. The new granular Bayluscide formulation was tested and found effective in large-scale aerial applications. A full-river rhodamine dye study successfully was conducted and the TFM transport model was recalibrated and refined.
Implementation of the sterile male release technique continued in Lake Superior and the St. Marys River. The sterilization facility continued to meet the needs of the program; 16,380 male lampreys were sterilized and released into streams in 1996. A four-year evaluation of the technique was initiated with experimental manipulation of populations of sea lampreys in eight streams.
The Barrier Task Force worked on expanding the development and use of sea lamprey barriers. To date, 54 barrier dams have been constructed or modified on Great Lakes tributaries to stop sea lamprey migration. In 1996, 1 barrier dam was constructed and 6 existing dams were modified to prevent passage of spawning sea lampreys.
The Assessment Task Force was established by the Great Lakes Fishery Commission in April and met in June and September. The Task Force proposed and implemented significant changes to the larval (Quantitative Assessment Protocol) and spawning-phase sampling programs. Stream and lake-wide population estimates are reported for each of the lakes.
The Lampricide Control Task Force was established in December 1995 and met in March and September. Options for saving TFM during treatments were established and prioritized. Treatment of the Rifle River in 1 ten-day series of applications (estimated 4 percent savings) and increased use of Bayluscide in 6 streams (estimated 5 percent savings) were authorized for 1997.
Studies to monitor the long-term effect of lampricide treatments on macroinvertebrate communities showed little significant impact. Adult and juvenile mussels of two species, Elliptio complanata and Anodonta cataracta were significantly less sensitive to TFM than sea lamprey larvae in flow-through toxicity tests. A total of 265 migrating lake sturgeon fry were captured and released between May 29 and June 14 in a drift net study designed to monitor the downstream movement of the fry in the Sturgeon River.
The sea lamprey management program conducted 463 outreach activities that required 298 staff days.
Table 1. Summary of lampricide treatments in streams of the Great Lakes
|Lake||Number of Streams||flow (M3/s)||TFM (1)(2) kg||Bayluscide (1) kg||Distance (km)|
(1) Lampricides are in kg of active ingredient.
(2) Includes 426 TFM bars (82 kg active ingredient) applied in 20 streams.
Table 2. Number and biological characteristics of adult sea lampreys
captured in assessment traps in tributariesof the Great Lakes in 1996.
|Lake||Number of Streams||Total captured||Number sampled||Percent males||Mean Length (mm)
|Females||Mean Weight (g)
Sea lamprey control is a critical fishery management action delivered to support the fish community objectives developed by the Lake Committees as part of the Strategic Plan for Great Lakes Fishery Management. Objectives for acceptable levels of mortality that allow the establishment and maintenance of self-sustaining stocks of lake trout and other salmonids have been established on all of the lakes. The Lake Committees have established specific targets for sea lamprey populations in the Fish Community Objectives for lake trout rehabilitation plans. The current control program reflects actions by the U.S. Fish and Wildlife Service (Service) and Department of Fisheries and Oceans Canada (Department) as contract agents of the Great Lakes Fishery Commission (Commission) to meet these targets.
The Commission is working in partnership with the Lake Committees through their Lake Technical Committees to refine the current target statements and to develop common target formats for each of the lakes. The Commission and cooperators will consider the costs of control along with the benefits to define a control program. The program must support the Fish Community Objectives, be ecologically and economically sound, and be socially acceptable. The target for each lake will define the abundance of sea lampreys that can be tolerated and the economically viable level of control required to reach the desired suppression.
This report presents the actions of the Service and Department in the integrated management of sea lampreys in the Great Lakes during 1996. Also, recent trends in lampricide use are related to the Commission vision and trends in sea lamprey abundance to Fish Community Objectives.
The Commission identified milestones in relation to the "Integrated Management of Sea Lamprey Vision Statement" that included:
Development and use of alternative control techniques to reduce reliance on lampricides to 50 percent of current levels.
Since the beginning of the use of lampricide in the management program, the Service and Department continually have increased their efficiency in the use of TFM. The combination of improved analytical, application, and assessment techniques, and construction of barriers has reduced the use of TFM for the period of 1990-96 (annual avg. of 40,000 kg) when compared to 1980-89 (annual avg. of 52,000 kg) (Fig. 1). This decrease has occurred despite the addition of streams to the treatment program with high TFM requirements due to high pH and total alkalinity.
FISH COMMUNITY OBJECTIVES
The Lake Superior Committee in 1990 established the following specific targets for sea lamprey populations in their Fish Community Objectives:
Achieve a 50% reduction in parasitic-phase sea lamprey abundance by 2000, and a 90% reduction in parasitic-phase sea lamprey abundance by 2010.
This sea lamprey target was developed to support the following objective for the community of lake trout and other salmonids.
Achieve a sustained annual yield of 4 million pounds of lake trout from naturally reproducing stocks, and an unspecified yield of other salmonid predators, while maintaining a predator/prey balance which allows normal growth of lake trout.
Naturally reproducing stocks of lake trout can only be maintained when total annual mortality is less than 45 percent. Reaching this objective for total mortality requires a combination of regulation of fishery exploitation and control of sea lamprey abundance.
The Service maintains an extensive trapping network for spawning-phase sea lampreys in index streams of the south shore of Lake Superior and annually estimates populations east and west of the Keweenaw Peninsula (Fig. 2). Populations east of the Peninsula generally remained stable during 1987-93, declined substantially in 1994, but increased again in 1995 and 1996. Populations to the west generally declined during 1989-95 and increased in 1996. The program achieved the sea lamprey target for Lake Superior (50 percent decline by 2000) in 1994 when compared to the 1986-90 average of 42,500 (13,700 in 1994). In 1996, the estimated population increased to 35,700 which is a decline of 16 percent of the 1986-90 average.
The Lake Michigan Committee established the following specific objective for sea lamprey populations in their Fish Community Objectives in 1995:
Suppress the sea lamprey to allow the achievement of other fish-community objectives.
In general, treatment of Lake Michigan tributaries over the past 25 years has provided sufficient control of sea lampreys, yet recent increases in lamprey wounding rates on lake trout in northern waters of the lake is a concern.
The sea lamprey objective was developed to support the other fish community objectives for Lake Michigan, for example the objective for lake trout and other salmonines:
Establish a diverse salmonine community capable of sustaining an annual harvest of 2.7 to 6.8 million kilograms (6 to 15 million pounds), of which 20-25 percent is lake trout. Establish self-sustaining lake trout populations.
Control of sea lamprey populations and fishery exploitation will be necessary to meet these fish-community objectives. The lake-wide management plan specifies four focus areas (refuges, primary, secondary, and deferred rehabilitation zones) in which lake trout rehabilitation has the best chance of success. The primary zones and refuges in which priority will be given to reducing mortality caused by sea lampreys include the mid-northern region of the lake, the mid-lake reef zone, and an offshore reef area in the southwest portion of the lake.
The Lake Huron Committee (1993) has established a specific objective for sea lamprey abundance as part of its Fish Community Objectives:
Reduce sea lamprey abundance to allow the achievement of other fish community objectives; obtain a 75% reduction in parasitic sea lamprey by the year 2000 and a 90% reduction by the year 2010 from present levels.
The progress toward this objective is measured by the abundance of spawning sea lampreys in four index streams in northern Lake Huron: Thessalon, St. Marys, Cheboygan and Ocqueoc rivers. Progress in reducing sea lamprey abundance aids in achieving objectives for the other species groups in the fish community including, for example, the salmonine community objective:
Establish a diverse salmonine community which can sustain an annual harvest of 5.3 million pounds, with lake trout the dominant species and anadromous species also having a prominent place.
To attain and maintain a self-sustaining lake trout population capable of supporting 3-4 million pounds of this overall yield objective the total annual mortality should not exceed 45 percent. The plan calls for management of exploitation of the fishery and control of lampreys to reach this objective. The lake-wide management plan identifies refuges and special rehabilitation zones in which rehabilitation is most likely to succeed. These priority zones, which are distributed throughout the lake, include the northern section and the North Channel. The plan specifies that these will be priority areas for the suppression of lampreys and control of fishery exploitation.
The Service and Department annually have trapped an average of 12 streams during 1986-96 to monitor abundance of sea lampreys in northern Lake Huron. During this period, abundance of lampreys generally increased but declined in 1994-96 (Fig. 4). These trap catches indicate an excessive number of sea lampreys in Lake Huron and the data are substantiated by similar patterns in indices of parasitic sea lamprey abundance and fish wounding. We suggest that without continued substantive action to manage the presently uncontrolled population of larvae in the St. Marys River we will fail to make progress in achieving sea lamprey objectives for lake trout rehabilitation in Lake Huron.
The Lake Erie Committee is currently developing Fish Community Goals and Objectives for the lake. The Committee is considering the previous management plans and will define objectives for the eastern basin salmonine community. The current draft in development recognizes the need for continuing control but does not set specific objectives for the sea lamprey.
The lake trout management plan for rehabilitation of self-sustaining stocks in the eastern basin of Lake Erie prescribed a maximum annual mortality rate of less than 40 percent be achieved to permit the establishment and maintenance of suitable stocks of spawning adults. Mortality would be controlled through management of fishery exploitation and continued suppression of sea lampreys.
The Service and Department annually have trapped spawning-phase sea lampreys in an average of seven tributaries since 1986 and estimated the number of spawning lampreys in Cattaraugus Creek during 1991-96 (Fig. 5). Current catches are significantly less than those prior to the start of lampricide management (started in 1986 and showed effect in spawner population in 1989) but are greater than 10 percent of pretreatment catches. The population remained stable from 1991-95 and increased in 1996. Wounding of lake trout measured in the fall of 1995 was 5.2 percent (wounding by lampreys spawning in 1996).
The Lake Ontario Committee (1988) in the Lake Ontario Fish Community Objectives supported continuing sea lamprey control and defined a specific objective for lampreys in terms of mortality to lake trout:
Limit the size of the sea lamprey population to a level that will not cause mortality in excess of 90,000 lake trout annually.
This specific objective was developed to support the productive salmonine community including a lake trout population that shows significant reproduction in the near term.
The Lake Ontario Committee has revised its Lake Ontario Lake Trout Rehabilitation Plan from the original plan developed in 1983. The goal of the plan is to rehabilitate the population of lake trout to a self-sustaining level as defined in the Fish Community Objectives. The plan includes the fundamental premise that continued control of sea lamprey induced mortality is necessary for lake trout rehabilitation. The plan includes a specific objective for sea lampreys:
Controlling sea lamprey so that fresh wounding rates (A1) of lake trout larger than 431 mm is less than 2 marks/100 fish.
This specific objective is meant to maintain the annual survival rate of 60 percent or greater in order to maintain a target adult spawning stock of 0.5 to 1.0 million adults of multiple year classes. Along with sea lamprey mortality, angler and commercial exploitation also will be controlled so that annual harvest does not exceed 120,000 fish in the near term.
The Service and Department annually have operated traps for spawning-phase sea lampreys in an average of 14 tributaries of Lake Ontario since 1986. In addition, the population of spawning lampreys was estimated for the Black and Humber rivers, and Duffins, Port Britain, and Shelter Valley creeks for 1992-96 (Fig. 6). During that period, catches have remained stable and have ranged from 4,000 to 8,000 annually.
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