A Case History of Sea Lamprey Control in Lake Huron: 1979 to 1999

J. Great Lakes Res. 29 (Supplement 1):599–614 Internat. Assoc. Great Lakes Res., 2003

A Case History of Sea Lamprey Control in Lake Huron: 1979 to 1999 Terry J. Morse1,*, Mark P. Ebener2, Ellie M. Koon3, Sidney B. Morkert3, David A. Johnson1, Douglas W. Cuddy4, John W. Weisser1, Katherine M. Mullett1, and Joseph H. Genovese1 1U.S.

Fish and Wildlife Service Marquette Biological Station 1924 Industrial Parkway Marquette, Michigan 49855

2Chippewa-Ottawa

Resource Authority 179 W. Three Mile Rd Sault Ste. Marie, Michigan 49783 3U.S.

Fish and Wildlife Service Ludington Biological Station 229 S. Jebavy Drive Ludington, Michigan 49431

4Department

of Fisheries and Oceans Sea Lamprey Control Centre 1 Canal Drive Sault Ste. Marie, Ontario P6A6W4

ABSTRACT. Sea lamprey (Petromyzon marinus) control on a lake-wide basis was initiated in 1970 and eventually reduced the original population of sea lampreys in Lake Huron by nearly 85%. Although some fish populations started to rebound after the first round of lampricide treatments, the recovery was shortlived and the population of parasitic-phase sea lampreys in the lake again began to increase largely because of the uncontrolled population in the St. Marys River. By 1994, the population of parasitic-phase sea lampreys in Lake Huron exceeded the combined populations in the four other Great Lakes. Lampreyinduced mortality rates on lake trout were greater than that recommended for recovering populations of lake trout. In response to the high lamprey-induced mortality rates, lake trout (Salvelinus naymaycush) were not stocked in the northern part of the lake from 1994 until 1997, when an integrated plan for sea lamprey control was implemented in the St. Marys River. Fish community objectives for sea lampreys in Lake Huron call for a 75% reduction in parasitic sea lampreys by the year 2000 and a 90% reduction by the year 2010. The integrated approach to the control of sea lampreys in the St. Marys River is projected to reduce the number of sea lampreys in Lake Huron by 85%. This exceeds the objective for 2000 and nears the objective for 2010. INDEX WORDS:

Lake Huron, sea lamprey, Great Lakes, lake trout, St. Marys River.

INTRODUCTION Lake Huron is one of five large freshwater lakes, known as the Laurentian Great Lakes located centrally along the 45th parallel in the North American continent. Three-quarters of the Lake Huron shoreline and two-thirds of the drainage area are in Canada. Manitoulin Island, the largest freshwater *Corresponding

island in the world, and the Bruce Peninsula divide the lake into three discrete basins; the North Channel, Georgian Bay, and the main basin of Lake Huron. The St. Marys River is the largest tributary with an average annual discharge of about 2,100 m3/sec. Sea lampreys, Petromyzon marinus, were first observed in a tributary of Lake Huron in 1937, when spawning adults were reported in the Oc-

author. E-mail: [email protected]

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queoc River, Presque Isle Country, Michigan (Applegate 1950). Lampricide control of larval populations in Lake Huron tributaries was first implemented in 1960 (Smith and Tibbles 1980). A total of 1,761 tributaries, 427 in the U.S. and 1,334 in Canada, discharge into Lake Huron and 116 of these, 62 in the U.S. and 54 in Canada, have historical records of sea lamprey production. This paper describes, in detail, changes in Lake Huron sea lamprey control and fish management practices since the Sea Lamprey International Symposium (SLIS) of 1979. HISTORIC FISH COMMUNITY Composition and abundance of the Lake Huron fish community changed dramatically during the twentieth century because of the introduction of non-indigenous species, habitat destruction, and overfishing (Berst and Spangler 1972). The annual commercial harvest from Lake Huron was constant from the early 1900s through 1930 and averaged about 9 million kg. Lake trout, Salvelinus namaycush, lake whitefish, Coregonus clupeaformis, lake herring, C. artedii, lake sturgeon, Acipenser fulvescens, deepwater ciscoes, Coregonus spp., and walleye, Stizostedion vitreum, were the primary targets of the fishery during the early 1900s. From 1930 to 1966, total commercial harvests declined continually from 11 million kg to 3.6 million kg (Berst and Spangler 1972). Lake trout were eradicated from Lake Huron by 1966, except for two small populations in Canadian waters of the North Channel and Georgian Bay. Four species of deepwater ciscoes had become extinct in the lake, and populations of lake whitefish, lake herring, and walleye were all severely depressed by the 1960s (Berst and Spangler 1973). The introduction of exotic species, especially sea lampreys, was catastrophic to a troubled Lake Huron fish community. Predation by sea lampreys was considered the leading cause of the collapse of populations of most fish species in Lake Huron (Berst and Spangler 1973, Coble et al. [1990). The collapse of lake trout and burbot, Lota lota, populations due to lamprey predation drastically reduced predation pressure on two other exotic species, alewives, Alosa pseudoharengus, and rainbow smelt, Osmerus mordax, and both species flourished (Berst and Spangler 1973). The Great Lakes Fishery Commission (GLFC) was established by the Convention on Great Lakes Fisheries between Canada and the United States,

which was ratified on 11 October 1955. The GLFC has two major responsibilities: 1) develop coordinated programs of research in the Great Lakes, and, on the basis of the findings, recommend measures which will permit the maximum sustained productivity of stocks of fish of common concern; and 2) formulate and implement a program to eradicate or minimize sea lamprey populations in the Great Lakes. The GLFC contracted the U.S. Fish and Wildlife Service (USFWS) and the Department of Fisheries and Oceans, Canada (DFO) as agents to conduct the operational element of the sea lamprey control program. A massive fishery management program was initiated in the late 1960s and early 1970s in response to the deterioration of the fish community of Lake Huron, and sea lamprey control was initiated in 1960 (Smith and Tibbles 1980). Commercial fisheries were severely restricted both in number of licenses and areas of operation by the State of Michigan (Brege and Kevern 1978) and the Province of Ontario. Large numbers of coho, Oncorhynchus kisutch, and chinook, Oncorhynchus tshawytscha, salmon were stocked to control expanding populations of smelt and alewife, and to provide a sport fishery (Ebener 1995). The process of rehabilitating lake trout populations began with stocking of hatchery-reared fish in 1974. SEA LAMPREY INTERNATIONAL SYMPOSIUM OF 1979 The first Sea Lamprey International Symposium (SLIS) was sponsored by the GLFC and had three objectives: 1) to organize, consolidate, and publish information on sea lamprey control and associated research; 2) to assemble experts in specialty areas related to sea lampreys to exchange knowledge and ideas and to bring everyone to a common level of understanding; and, 3) to provide a forum for the participating scientists to develop new imaginative initiatives and stimulate new vigor in dealing with the effort to control sea lamprey predation and understand fish-lamprey interactions (Smith 1980). During the 1979 SLIS, Walters et al. (1980) made nine recommendations to improve sea lamprey control and relate this control to other fisheries management activities: 1) improve the chemical treatment program; 2) require statistically sound designs and intensive monitoring schemes for pilot experiments that involve alternative control techniques; 3) study streams colonized by sea lampreys after pollution abatement; 4) search for natural con-

Sea Lamprey Control in Lake Huron trol for sea lampreys; 5) conduct large-scale experiments on the effects of reduced sea lamprey control and overfishing; 6) review and revise salmonid stocking programs; 7) restrict exploitation rates on lake trout; 8) develop a comprehensive fishing policy for species impacted by sea lamprey predation; and 9) develop a rehabilitation program for native forage species. Since the 1979 SLIS, all of the recommendations concerning sea lampreys were implemented in Lake Huron. The use of TFM has been reduced through various means since 1980 (Brege et al. 2003). The frequency of lampricide treatments has been reduced through the use of more accurate estimates of sea lamprey production in stream treatment selection (Christie et al. 2003). Studies relating to three promising alternative control techniques, sterile-male-release, barriers, and attractants, have been completed or are in progress. In addition, extent and density of infestations of larval sea lampreys have been estimated for Lake Huron tributaries. Most of the fisheries-related actions recommended by Walters et al. were also implemented on Lake Huron. A refuge was created in northern Lake Huron, where the effects of an uncontrolled sea lamprey population could be evaluated on an unfished lake trout population (Eshenroder et al. 1995, Ebener 1998). Two other refuges, one in Georgian Bay and the other in the main basin, were established to protect lake trout in areas of moderate sea lamprey abundance and low fishing mortality, and low sea lamprey abundance and moderate fishing mortality. Eight strains of lake trout have now been integrated into the lake-wide stocking program (Ebener 1998), and experiments in progress are evaluating success of each strain. Stocking rates of most other salmonines have been reduced or stabilized since 1990 because of concerns about the effects of over-stocking on forage species or because of fish health concerns with chinook salmon. Lake trout stocking has increased from 0.8 million fish in 1990 to 4.1 million fish in 1998 (Ebener et al. 1995, Ebener 1998), although these stocking rates were less than recommended levels (Ebener 1998). Restrictions on the recreational and commercial harvest of lake trout in Lake Huron were implemented, although total mortality rates exceeded recommended levels in some parts of the lake. COORDINATED FISHERY MANAGEMENT The GLFC provides the forum for the various Great Lakes management agencies to work together

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in an ecosystem approach to manage fish species of mutual concern in Lake Huron. Two Lake Huron committees operate within the GLFC structure, the Lake Huron Committee (LHC) and the Lake Huron Technical Committee (LHTC). The LHC developed Fish Community Objectives (FCOs) for Lake Huron in 1995 with the overall objective to “over the next two decades restore an ecologically balanced fish community dominated by top predators and consisting largely of self-sustaining, indigenous, and naturalized species capable of sustaining an annual harvest of 8.9 million kg” (DesJardine et al. 1995). The FCO for sea lamprey is to “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 90% reduction by the year 2010 from present levels” (DesJardine et al. 1995). The LHTC serves the LHC by monitoring the status of the Lake Huron fish community, developing plans for rehabilitation of lake trout (Ebener 1998), and making recommendations for management of the fish community to the LHC. The LHTC also was charged with developing a plan for management of sea lampreys in Lake Huron. Since sea lamprey control is a critical fishery management action delivered in support of the FCOs, the control agents were given representation on the LHTC in the early 1990s. The status of the Lake Huron fish community in relation to FCOs was published in 1995 (Ebener 1995) and provided a base for measurement of progress toward achieving the objectives, including the sea lamprey objective. LAMPRICIDE CONTROL IN LAKE HURON Between 1960 and 1999, 620 lampricide applications were conducted on 92 Lake Huron tributaries (Table 1). The average number of tributaries treated annually decreased from 22 per year during 1970 to 1979 to 15 per year during 1980 to 1999, a reduction of 32%. The average number of km of tributary treated annually also decreased 40% during the same period, from 615 km during 1970 to 1979 to 365 km during 1980 to 1999. Reductions in the number and length of tributaries treated was due to 1) failure of sea lampreys to reestablish in some tributaries after initial treatments; 2) reductions in treatment effort applied to Lake Huron tributaries to accommodate additional new efforts to treat tributaries in Lake Erie after 1986; and 3) success of new barriers in reducing infested areas of streams.

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TABLE 1. Streams tributary to Lake Huron that received lampricide applications during 1966 to 1999, llisted by category for production of sea lamprey larvae. Also listed are the estimated amount (m2) of types 1 and 2 habitats for sea lamprey larvae. [Category refers to relative lampricide treatment frequency and relative productivity for sea lamprey larvae and transformers. Category 1 streams were treated on a cycle that ranges from about ≥ 1.4 to ≤ 5 years, have been treated at least once during 1990 to 1999 and have been productive for sea lampreys. Category 2 streams were treated at least once during 1990 to 1999 but the cycles were less frequent than category 1 streams, and generally are less productive than category 1 streams. Category 3 streams have not been treated during 1990 to 1999 and are relatively unproductive yet have produced some sea lamprey larvae.]

Country Stream Category 1 Streams Can./U.S. St Marys River Canada

U.S.

Pine River Sturgeon River Magnetewan R. Blue Jay Creek Manitou River Timber Bay Cr. Mindemoya R. Wanapitel R. Silver Creek Serpent River Spragge Creek Mississagi R. Thessalon River (Lower) Koshkawong R. Browns Creek Gordon Creek Watson Creek Sucker Creek Echo River (Upper) Garden River Root River Albany Creek Trout Creek Beavertail Cr. McKay Creek Pine River Carp River L. Munuscong R. Munuscong. R. Taylor Cr. Cheboygan River Maple River Pigeon River Sturgeon River Elliot Creek

Total 1958 to 1999

TFM Treatments Year last treated

Estimated Habitat(m2)1 Mean frequency2

Type 1

Type 2

13

1999

4 9 9 8 8 3 8 6 6 9 2 9

1998 1999 1999 1999 1999 1998 1998 1994 1994 1999 1995 1995

2.3 4.9 4.9 4.3 4.3 4.5 4.1 5.0 4.4 4.8 5.0 4.2

45,134 4,630 9,252 35,359 468 7,114 12,720

231,779 9,248 10,036 57,675 2,910 17,578 4,560

7,602 682 98,381

69,077 2,330 2,669,385

8 9 10 9 9 10

1996 1997 1998 1996 1998 1995

4.1 3.9 4.1 4.4 4.0 3.8

25,650 4,195 3,545 1,565 1,520 2,544

339,610 6,257 6,177 4,094 5,451 1,063

10 11 11

1999 1997 1999

3.4 3.1 3.8

3,496 1,698

928,792 44,017

14 9 8 9 9 11 10

1994 1994 1996 1995 1998 1996 1999

2.2 3.5 4.3 3.6 4.0 3.0 4.2

30,354 4,620 20,275 3,783 229,115 109,146 6,396

15,325 2,664 17,586 13,940 371,878 325,536 39,980

9

1999

4.6

8,599

43,645

8 9 8 8

1998 1997 1999 1996

4.6 3.9 4.7 4.3

3,205

8,577 (Continued)

Sea Lamprey Control in Lake Huron TABLE 1.

Continued.

Country Stream Category 1 Streams (Continued) U.S. Greene Creek Mulligan Creek Black Mallard Ocqueoc River Lower Upper Schmidt Creek Trout River Devils River Au Sable River Tawas River Silver Creek East Au Gres R. Au Gres River Hope Creek Rifle River Saginaw River Chippewa R. Category 2 Streams Canada Chikanishing R. Sand Creek Spanish River No Name (H-114) Lauzon Creek Pickerel Cr. Livingstone Cr. Thessalon River Upper Rock to Gordon Wood Cr. Carpenter to Rock Richardson Cr. Two Tree River Echo River Lower Nottawasaga R. Musquash R. Boyne River Naiscoot River Still River Sable River U.S.

603

Ceville Creek Hessel Creek Nuns Creek Martineau Creek Cheboygan River Meyers Creek

Total 1958 to 1999

TFM Treatments Year last treated

Estimated Habitat(m2)1 Mean frequency2

Type 1

Type 2

8 7 7

1996 1994 1992

4.1 4.7 4.2

3,490

3,429

1,819

30,017

15 9 8 9 7 9

1997 1998 1998 1997 1995 1998

2.1 3.8 4.4 3.8 4.5 3.5

16,435 57,739 4,266 13,228 26,800 145,666

70,062 234,652 18,947 38,470 45,967 817,484

7 10 9 8 10

1997 1997 1997 1996 1997

4.7 3.1 3.6 4.0 3.1

12,757 12,713 91,816 18,049 241,332

47,717 119,691 292,097 34,088 1,946,418

6

1999

4.0

292,182

2,349,666

7 4 5 3 7 1 3

1995 1994 1998 1997 1997 1998 1994

5.8 7.0 7.8 18.0 6.0

6,812 2,120

2,511 3,549

1,287 299

2,897 3,202

16.5

1,209

8,150

3 1 1 1 6 5

1998 1990 1990 1991 1996 1990

15.5 23,228 4,174 6,174

113,909 6,194 5,514

5 4 3 7 8 7 5

1994 1997 1996 1999 1999 1996 1996

6.8 12.0 13.0 6.5 5.6 6.0 6.5

122,660 170,942 26,722

452,738 71,272 5,312

24,897 63,855

53,934 71,115

3 5 5 4

1994 1991 1996 1993

8.0 5.3 6.5 7.7

3,747

2,012

4

1999

9.3

958

7.0 7.2

4,299 (Continued)

604 TABLE 1.

Morse et al. Continued.

Country Stream Category 2 Streams (Continued) U.S. Little Pigeon Swan River Black River Au Sable River Pine River Tawas River Cold Creek Sims Creek Saginaw River Shiawassee R. Prentiss Creek

Total 1958 to 1999

Category 3 Streams Canada Bayfield River Saugeen River Sydenham River Bothwells Creek Big Head River Beaver Creek Pretty River Nottawasaga River Mad River Lafontaine Creek Hog Creek Shebeshekong R. Key River (Nisbet Creek) French River Western Channel Kaboni Creek Kagawong River Serpent River Grassy Creek Blind River McBeth Creek Unnamed (H-68) Unnamed (H-65) Bar River U.S.

Mission Creek Frenchette Creek Ermatinger Creek Charlotte River Munuscong River Canoe Lake Outlet Carlton Creek Bear Lake Outlet Carr Creek Joe Straw Creek Saddle Creek

TFM Treatments Year last treated

Estimated Habitat(m2)1 Mean frequency2

Type 1

Type 2

4 6 3

1998 1996 1998

6.7 5.8 15.0

4,146 6,099 20,592

18,225 28,494 58,071

5 2 5 2

1987 1996 1996 1998

5.3 29.0 7.3 31.0

3,261 1,696

11,587 5,096

3 6

1997 1993

6.5 5.4

6,430

1,091,923

1 1 2 3 0 0 1

1970 1971 1972 1979

4.0 3.5 30,582

142,997

4 2 1 1 1

1976 1968 1978 1999 1972

5.0 7.0 15,714

17,681

2 3 1

1992 1978 1967

16.0 4.5 4,195

6,257

2 3 2 3 2 1

1996 1984 1967 1975 1975 1966

26.0 6.5 6.0 4.0 8.0

632 0

3,094 6,212

1,081

1,519

65

454

0 0 0 1 6 1 4 2 3 2 0

1972

1981 1982 1970 1986 1977 1978 1975

4.0 8.0 4.0 6.0 9.0

(Continued)

Sea Lamprey Control in Lake Huron TABLE 1.

605

Continued. TFM Treatments Year last treated

Estimated Habitat(m2)1

Total 1958 Mean Country Stream to 1999 frequency2 Type 1 Type 2 Category 3 Streams (Continued) U.S. Huron Pointe Cr. 0 Flowers Creek 1 1983 Steels Creek 5 1984 4.5 McCloud Creek 1 1972 266-20 Creek 1 1976 Beaugrand Creek 1 1976 Little Black R. 1 1967 Cheboygan River 2 1983 5.0 Laperell Creek 3 1989 11.5 Grass Creek 3 1978 4.0 Grace Creek 4 1977 3.3 Seventeen Creek 1 1967 Johnny Creek 1 1970 Grand Lake Outlet 0 Middle Lake Out 1 1967 Squaw Creek 1 1967 Saginaw River Flint River 0 Cass River 1 1984 Juniata Creek 1 1998 10,328 22,313 Pine River 1 1988 Big Salt River 2 1993 8.0 8,422 148,080 Big Salt Creek 2 1996 8.0 Carroll Creek 1 1988 3,822 24,360 Rock Falls Creek 0 Sucker Creek 0 Cherry Creek 0 Mill Creek 2 1985 4.0 1Calculated by defining the habitat into Type 1 (preferred) or Type 2 (acceptable) across a number of transects throughout the stream. Where no numbers are provided, no estimates were made. 2Calculated by subtracting the first treatment year from the last treatment year and dividing by the number of treatments minus one. 3Spot-treatment was conducted with Bayluscide granules in 1999.

The St. Marys River is the largest tributary to Lake Huron. Larval sea lampreys were first discovered in the St. Marys River in 1962. In 1991, the Sea Lamprey Integration Committee (SLIC) charged the agents to form a St. Marys River Control Task Force (task force) to develop a unified strategy for control of sea lampreys in the river. The task force developed a two-pronged control strategy that focussed on: 1) removal of sea lamprey larvae from the river with lampricide, and 2) reducing recruitment of sea lampreys to the river through alternative control efforts, which included trapping and removal of spawning-phase sea lampreys and introduction of the Sterile-Male-Release Technique (SMRT).

The St. Marys River harbored an estimated 5.2 million sea lamprey larvae in 1996 (Fodale et al. 2003) but had a discharge rate too great to treat with TFM. After an extensive survey in 1993 to 1996, areas of high larval density were treated in 1998 (80 ha) and in 1999 (780 ha) with granular Bayluscide. As a result the population of sea lamprey larvae in the river was reduced by an estimated 45% (Schleen et al. 2003). Changes in Treatment Techniques The general procedures used to prepare for a stream treatment and apply TFM (Smith et al. 1974,

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Morse et al.

Smith and Tibbles 1980) have changed little since 1979, but improvements in instrumentation and techniques have refined the ability to predict TFM toxicity and to maintain effective concentrations of lampricide. Regressions relating the toxicity of TFM to pH and total alkalinity of stream water (Bills et al. 2003), flow-through toxicity testing systems (Bills and Johnson 1992), and other procedural improvements (Brege et al. 2003) have helped to reduce the amount of TFM needed during treatments. The mean weights of TFM active ingredient applied per unit of discharge (m 3 /sec) for the decades of the 1960s through the 1990s were 211, 169, 158, and 131 kg, respectively. This is a 38% reduction in the rate of application between the 1960s and 1990s (Brege et al. 2003). The Rifle River is one of the larger watersheds on the U.S. side of Lake Huron and a major producer of sea lampreys. The watershed is not only large, but also dendritic. Because of personnel limitations, treatment of the Rifle River and its 19 tributaries were normally conducted in segments and required about 30 days to complete. USFWS and DFO treatment crews were combined to treat the river in one continuous treatment in 1997. This combined effort was successful and resulted in a reduction of lampricide used of nearly $100,000. Treatment time was also reduced from 30 days to 8. Stream Selection Process for Lampricide Control One of the recommendations of SLIS was to implement a program of integrated pest management for sea lampreys in the Great Lakes. A strategic plan for the integrated management of sea lamprey (IMSL) was presented to the GLFC in 1982 (Davis and Manion 1982). The goal of IMSL was to provide an integrated sea lamprey management plan that supports the FCOs for each of the Great Lakes that is ecologically and economically sound and socially acceptable (GLFC 1992). A system for selecting streams for treatment (Empiric Stream Ranking System) evolved out of IMSL. The process in this cost-effective system compares the cost of treating a stream with the estimated number of parasitic sea lampreys that the tributary would contribute to the lake if no control was implemented. The cost effectiveness of lampricide treatments of each lamprey-infested tributary to Lake Huron is compared to the cost effectiveness of treatments of all other infested tributaries in the Great Lakes to produce a basin-wide hierarchical

list of candidate streams for lampricide treatments each year. ALTERNATIVE CONTROL METHODS IN LAKE HURON Barriers The GLFC continues to seek additional methods of sea lamprey control to reduce alliance on chemical lampricides and increase the efficiency of the program. Barriers to migrating sea lampreys in tributaries can significantly reduce the spawning potential of sea lampreys in the Great Lakes (Lavis et al. 2003). Barriers, whether natural or man-made, help restrict the access of sea lampreys to many Great Lakes streams. Denny’s Dam, constructed on the Saugeen River in 1970, was the first low-head barrier built specifically to block sea lampreys in a Lake Huron tributary. By 1999 17 structures (Fig. 1) on Lake Huron tributaries had been either constructed as dedicated sea lampreys barriers or were modified to function as such. These barriers block spawning-phase sea lampreys from more than 450 km of stream. Barriers have been effective for 227 of 246 barrier-years of operation, a success rate of 92%. Sterile-Male-Release Technique The technique consists of capturing adult sea lampreys during the spring spawning migration in Great Lake tributaries, destroying the females, sterilizing the males, and placing the sterilized males into a designated stream to spawn with remaining females (Twohey et al. 2003). The St. Marys River is the only stream basin-wide where the sterile male release technique is currently being implemented. Sterilized males were first placed in the river in 1991. Beginning in 1997 all available sterilized males were placed in the St. Marys River as part of an integrated sea lamprey control strategy for the river. The technique was integrated with an enhanced trapping program and the treatment of select locations with a granular, bottom-release formulation of Bayluscide (Schleen et al. 2003). Long-term evaluation of the integrated control strategy is based on estimates of larval abundance from a stratified random sampling methodology using a deepwater electrofisher, spawning populations in the river and other Lake Huron tributaries from mark recapture studies in the trapping program, and annual wounding rates on salmonids in Lake Huron. (Adams et al. 2003).

Sea Lamprey Control in Lake Huron

Stream A. Albany Creek B. Nuns Creek C. Ocqueoc River D. Trout River E. East Br. Au Gres River F. West Br. Rifle River G. Shiawassee River H. Saugeen River I. Sturgeon River J. Harris Creek K. Still River L. French River M. Manitou River N. Blind River O. Browns Creek P. Koshkawong River Q. Echo River

FIG. 1.

Year of construction 1985 1997 1999 1997 1983 1997 1998 1970 1979 1958 1986 1979 1983 1971 1998 1980 1986

Kilometers upstream of barrier 8.7 4.8 36.0 14.1 38.9 11.0 63.2 80.0 20.4 7.3 13.2 57.9 11.9 23.8 2.9 15.0 42.2

607

Years of operation 14 2 — 2 16 2 1 29 20 41 13 29 16 28 1 19 13

Sea lamprey barriers on Lake Huron tributaries, 1970 to 1999.

MANAGING RISK TO NONTARGET ORGANISMS During the 1979 SLIS, Gilderhaus and Johnson (1980) reported that some mortality of nontarget organisms occurred during lampricide treatments in

the Great Lakes. Advancements in the control program after 1980 included additional effort for monitoring and reporting treatment effects on nontarget organisms. The pace of investigations of effects of lampricide control on nontarget organisms acceler-

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Morse et al.

ated, and six studies have been conducted on Lake Huron tributaries since 1985 (Schuldt and Sullivan 1985, Sorgenfrei 1990, Kaye 1995, Noakes et al. 1999, Boogaard et al. 2003, Weisser et al. 2003). The findings from these studies are consistent with studies conducted by the USFWS and independent investigators throughout the Great Lakes basin, and show that most nontarget organisms are more tolerant to lampricides than sea lampreys. A few sensitive nontarget organisms die during treatments, but the long-term health of the aquatic communities remains diverse and abundant in the treated areas. Lampricide applications are managed to protect federal and state-listed endangered and threatened species, and to minimize the risk to other sensitive nontarget organisms. SEA LAMPREY LARVAE IN LAKE HURON TRIBUTARIES Sea lamprey larvae had been detected in 102 of 1,761 tributaries to Lake Huron before 1979 (Smith and Tibbles 1980). Since 1979, 14 more lampreyproducing tributaries have been found. Of the 116 tributaries, 11 have never been treated and 23 streams were treated only once due to very small populations of larvae (Table 1). Most tributaries that were never infested have limiting factors, such as cold ambient water temperature, steep gradient, limited spawning grounds, limited larval habitat, and physical barriers to upstream migration (Smith et al. 1974). The Saginaw River, located in the east central lower peninsula of Michigan (Fig. 2), is the second largest U.S. tributary to Lake Huron. Enacted water

FIG. 2. Estimated numbers of spawning-phase sea lampreys in Lake Huron, 1979 to 1999.

quality legislation was expected to enhance sea lamprey production and survival in Great Lakes tributaries (Walters et al. 1980). Morman et al. (1980) reported that pollution abatement allowed establishment of a sea lamprey population in the Peshtigo River on Lake Michigan. This has also occurred on the Saginaw River system, where only one tributary was treated before 1979, but 20 lampricide treatments have been needed on nine tributaries since 1979. Continued pollution abatement will probably allow greater spawning success, larval survival, and range expansion of sea lampreys throughout the Saginaw River system and other Great Lakes tributaries. HISTORICAL ABUNDANCE OF SPAWNING-PHASE AND PARASITIC-PHASE SEA LAMPREYS Initial efforts to control adult sea lampreys in Lake Huron were targeted at limiting spawning migrations by constructing mechanical weirs in streams used for spawning. The State of Michigan installed the first mechanical sea lamprey weir on the Ocqueoc River in 1945 to study the biology of the sea lamprey (Smith and Tibbles 1980). A permanent mechanical weir and trap were installed on the Ocqueoc in 1949 and converted to an electromechanical weir in 1952. The GLFC approved the installation of 12 electrical weirs on 11 tributaries along the Canadian side of the lake in 1964, but only 8 of the devices were operated continuously from 1967 to 1975. The electrical weirs proved to be ineffective for control purposes and were operated to assess spawning-phase populations of sea lampreys before the weirs were removed from operation. Portable traps were used in Lake Huron tributaries after 1977 to capture spawning-phase sea lampreys during spring migrations and estimate their abundance (Schaefer 1951, Mullett et al. 2003). From 1979 to 1999, the population of spawning-phase sea lampreys produced in Lake Huron was estimated by summing population estimates from individual sea lamprey producing tributaries. The estimated population in those tributaries where traps were absent was predicted on the basis of tributary drainage area, geographic region of the lake, primary or secondary classification, year, and the number of years since the last treatment (Mullett et al. 2003). The estimated abundance of spawning-phase sea lampreys for Lake Huron (Fig. 2) varied without

Sea Lamprey Control in Lake Huron trend from 1979 to 1999 (t = 1.91, p = 0.07, R2 = 0.16), and ranged from 80,000 in 1980 to 420,000 in 1993. The significant element of this population trend was that abundance was consistently high and in most years exceeded all of the other Great Lakes combined. There were five estimates of the population of parasitic-phase sea lampreys in Lake Huron during 1979 to1999. Heinrich et al. (1985) estimated about 250,000 during 1981, and Bergstedt et al. (2003) estimated 515,000 in 1993, 629,000 in 1994, 1,361,000 in 1998, and 1,759,000 in 1999. Population estimates during the parasitic-phase would be expected to be higher than the spawning-phase because of mortality experienced during migration to the lake and the first several months of parasitic feeding. The large estimates of 1998 and 1999 were discounted because Bergstedt et al. (2003) attributed those to a change in handling of animals between capture and release (resulting in lower survival) and/or a change in Lake Huron or its fish community that reduced the probability of a released animal successfully resuming parasitic feeding. Given the relatively wide 95% confidence intervals of the parasitic-phase estimates (Bergstedt et al. 2003), the estimates of parasitic-phase sea lampreys for 1981, 1993, and 1994 compared well to the spawning-phase estimates for 1982, 1994, and 1995 of 180,000 to 210,000. SOURCES OF PARASITIC SEA LAMPREYS The parasitic-phase sea lampreys in Lake Huron came from two major sources; sea lampreys from untreated sources, and sea lampreys that survived lampricide treatments (residuals). Before 1998, the St. Marys River supported the largest untreated population (> 5 million) of sea lamprey larvae and annually produced the majority of the parasitic sea lampreys in Lake Huron (Schleen et al. 2003). Young et al. (1996) found that increases in the abundance of prey fish during the 1970s and early 1980s had strong correlation with the pattern of increased abundance of sea lampreys, and concluded that improved survival of metamorphosing sea lamprey larvae produced in the St. Marys River contributed to the observed increase in parasitic-phase sea lampreys in Lake Huron. Increased survival of metamorphosing larvae from the St. Marys River would explain the increase in the parasitic-phase population in Lake Huron while the spawningphase population remained static over the same period.

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Another possible source of untreated populations of sea lampreys is lentic populations offshore of sea lamprey producing tributaries. However, no tributaries to Lake Huron have been identified by larval assessments as having lentic populations large enough to require annual treatments. There are several reasons why a population of sea lamprey larvae may not be treated. First, a population might remain undetected. However, larval assessment in Lake Huron tributaries has been aggressive in identifying streams that contain populations of sea lamprey larvae. On the basis of larval assessments, the contribution of parasitic-phase sea lampreys from undetected sources is believed to be minimal. Second, a stream may not be treated because of cost-effectiveness or feasibility. Concerns of cost-effectiveness most often cause deferral of stream treatments, and this, in turn, results in the greatest contribution of lampreys from untreated tributaries. There is no doubt that TFM treatments are less than 100% effective, and outside of the contribution by the St. Marys River, many parasitic sea lampreys in Lake Huron come from residual populations. The largest streams have the largest areas of favorable habitat and produce the majority of metamorphosing sea lamprey larvae that enter the Great Lakes (Christie et al. 2003). Most sea lamprey larvae reside in about 45 large Lake Huron tributaries and are treated regularly (Table 1). Lampricide treatments in these tributaries are generally 80 to 95% effective (Smith and Tibbles 1980). Sea lamprey larvae escape lampricide treatment in oxbows, backwaters, and areas of groundwater influx where minimum lethal concentrations of lampricide are difficult to maintain. As many as 100,000 larvae may survive a 90% effective treatment of a tributary with a larval population of one million. The production of juvenile sea lampreys from populations of residual larvae can result in a significant impact to the Lake Huron fish community. The criteria used for selecting tributaries for treatment changed in 1995. Since 1995, streams have been selected for treatment from rank-ordered lists, with staff time the limiting resource (Christie et.al. 2003). Before 1995 most major sea lamprey producing tributaries were treated on a 3 to 4 year cycle based on relative abundance of larval populations and the time required for sea lamprey larvae to metamorphose into parasitic-phase juveniles. Many other tributaries were treated every 5 to 6 years and a few at intervals greater than 6 years. Since 1995, quantitative estimates of the escape-

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ment of metamorphosing sea lampreys were used in cost-benefit analysis to select tributaries. More tributaries required lampricide treatments than there were resources available. EFFECTS OF SEA LAMPREYS ON HOST FISH Before Sea Lamprey Control Evidence of the effects of sea lamprey predation on lake trout prior to sea lamprey control in Lake Huron came primarily from Canadian records. Fry (1953) reported that in South Bay, Manitoulin Island, sea lamprey marking rates on lake trout increased on all lengths of fish during 1947 to 1950. He attributed the decrease in numbers of lake trout harvested (21,000 in 1948 to only 600 in 1951) to excessive mortality caused by sea lampreys. Tomkins (1951) reported that in Georgian Bay 30% of lake trout 178 to 864 mm and 43% of lake trout longer than 430 mm bore sea lamprey marks. Budd and Fry (1960) concluded that because sea lamprey marking rates of lake trout increased with age (4% at age 3, 38% at age 4, and 66% at age 5), there would be no difficulty in re-establishing a population of lake trout in South Bay if sea lampreys were controlled. Reid et al. (2001) reported 33 to 39 A1A3 sea lamprey marks per 100 fish on lake trout caught in Parry Sound in 1958. Other fish species were also attacked in Lake Huron prior to sea lamprey control. Hall and Elliott (1954) reported increased marking rates on white suckers, Catostomus commersoni, caught in Hammond Bay northern Lake Huron, in 1951. In Michigan tributaries the percentage of returning, mature cohos that bore sea lamprey marks was 73% in 1969 and 58% in 1970 (Johnson et al. 1995). Spangler et al. (1980) estimated that 75% of the sea lamprey attacks on lake whitefish were fatal during mid-June to mid-November, and that sea lamprey induced mortality was 29% on age 3 to 5 lake whitefish in northern Lake Huron in the mid to late 1960s. Although commercial fishing also contributed to the decline of fish stocks in Lake Huron, there is little doubt that sea lampreys had a more pervasive effect on the fish community. A model of the dynamics of sea lamprey predation on lake trout (Jensen 1994) indicated that near extinction of lake trout in Lake Huron would have resulted with or without a commercial fishery. Coble et al. (1990) re-examined the role of commercial fishing in the demise of lake trout in the Great Lakes and found

no convincing evidence of overfishing in Lake Huron and Lake Michigan, however, this conclusion was questioned by Eshenroder et al. (1995). Berst and Spangler (1972) considered the sea lamprey the critical factor in the final demise of the lake trout in Lake Huron. After Sea Lamprey Control Sea lamprey control has been successful at reducing the number of sea lampreys in Lake Huron. Lake whitefish populations recovered quickly in the main basin (Reckahn 1995) and in South Bay after initiation of chemical control in 1970. Numbers of stocked lake trout increased at many locations in the lake (Eshenroder et al. 1995). Reproduction was documented at several locations, but the amount of reproduction was not sufficient to sustain the population ( Anderson and Collins 1995, Johnson and VanAmberg 1995, Reid et al. 2001). A standardized format for tabulation of sea lamprey marking data was adopted in 1984 to increase the utility of the marking data for studying the effects of sea lampreys on the fish community of Lake Huron (Eshenroder and Koonce 1984). The reporting format followed the mark classification system developed by King (1980) and required the reporting of the total number of A1, A2, and A3 sea lamprey marks per 100 fish examined. The A1 mark indicates a fresh and very recent attack in which the sea lamprey penetrated both the skin and musculature of the fish, whereas the A2 and A3 marks represent varying degrees of healing. Marking statistics for lake trout are reported for each of four standard size categories; 432 to 532 mm, 533 to 634 mm, 635 to 736, and > 736 mm total length. Sea lampreys continue to have a pervasive effect on the Lake Huron fish community even after 30 years of chemical control. In St. Martin Bay in northwestern Lake Huron, 11 of 18 fish species captured in trap nets in April and May 1991 to 1995 bore sea lamprey marks. No marks were observed on yellow perch, smallmouth bass, small lake whitefish, splake, and round whitefish, whereas marking rates ranged from 2 to 146 marks per 100 fish among the other species. The highest rates were observed on channel catfish (Fig. 3). Sea lamprey marking rates were greater on lake trout than chinook salmon or lake whitefish of comparable size in northern Lake Huron during 1982 to 1999 (Fig. 4). This suggests that either lake trout are the primary target of sea lampreys in northern Lake Huron or they survive the attacks better.

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FIG. 3. Mean A1-A3 sea lamprey marking rates observed on 16 species of fish caught in trapnets in St Martin Bay, Lake Huron, during April to May, 1991 to 1995. Marking rates on lake trout are greatest in northern Lake Huron and decrease from north to south (Fig. 5). During 1986 to 1999 marking rates of 400 to 500 mm lake trout averaged nine marks per 100 fish in the north, five marks per 100 fish in the central basin, and four marks per 100 fish in the south (Johnson et al. 2000). The same pattern of marking takes place on lake trout 500 to 600 mm with annual marking rates ranging from a high of 40 marks per 100 fish in the north to less than 20 marks per 100 fish in the southern basin. Sea lampreys were believed to be the primary source of lake trout mortality in most areas of Lake Huron. Johnson et al. (1995) estimated that sea lamprey induced mortality among the four standard size classes of lake trout ranged from 16 to 56% in the north, 8 to 34% in the central, and 6 to 32% in the southern basin during 1991 to 1992. Sitar (1996) and Sitar et al. (1999) reported that sea lamprey-induced mortality accounted for most of the lake trout deaths in central and southern Lake Huron during 1984 to 1993. Lamprey-induced mortality rates on lake trout are greater than the maximum total mortality rates recommended for recovering populations of lake

FIG. 4. A1-A3 sea lamprey marking rates observed on lake trout, chinook salmon, and lake whitefish caught in the Chippewa-Otttawa Research Authority commercial fishery of northern Lake Huron from 1980 to 1999, by 100 mm intervals of total length.

trout (Ebener 1998). In response to the high mortality rates on lake trout inflicted by sea lampreys, the LHTC recommended cessation of stocking of lake trout in the northern part of the lake until the GLFC submitted a plan and time frame for controlling the population of larvae in the St. Marys River. Stocking was discontinued from 1994 to1997, then resumed when an integrated plan for sea lamprey control in the river was implemented. OPTIMAL FUTURE CONTROL, AND FISH COMMUNITY OBJECTIVES (FCOs) FOR SALMONINES The FCOs for Lake Huron call for a 75% reduction in parasitic sea lampreys by the year 2000 and

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Morse et al. 8 and older lake trout would increase 232% by 2010 in northern Lake Huron if the maximum mortality rate was no more than 45% on these adult fish. However, if sea lamprey-induced mortality rates were reduced to 25% of the 1993 rate of 77%, projected numbers of mature female lake trout would increase 2,039%. The ability to achieve the overall FCO for Lake Huron salmonines is directly related to the level of sea lamprey control in the St. Marys River and other tributaries. With no significant increase in fishing mortality, and achievement of the targeted 85% reduction in sea lamprey numbers in the St. Marys River, the prediction is that the FCOs for salmonines and sea lamprey will be achieved. ACKNOWLEDGMENTS We thank Dr. Gerald Matisoff, Editor; Mike Jones, Guest Editor; and John Heinrich, Guest Associate Editor for their assistance and comments, and Jean Adams for her assistance with statistics. We also thank the Great Lakes Fishery Commission for hosting the Sea Lamprey International Symposium. REFERENCES

FIG. 5. A1-A3 sea lamprey marking rates on four length classes of lake trout caught in gill net surveys during May through June 1986 to 1999. Rates reported by statistical district in Michigan waters of Lake Huron. a 90% reduction by the year 2010 (DesJardine et al. 1995). The integrated approach to the control of sea lampreys in the St. Marys River, implemented in 1997, is projected to reduce the number of sea lampreys in Lake Huron by 85% (Schleen et al. 2003). This exceeds the objective for 2000 and nears the objective for 2010. With this projected decrease in sea lamprey numbers in Lake Huron, the spawning potential of lake trout and other salmonines is projected to increase rapidly to levels necessary to sustain objectives for annual production. Sitar (1996) reported that during 1984 to 1993, estimated total mortality for lake trout ages 3 to 10 in northern Lake Huron was very high and exceeded the target maximum total annual mortality rate of 45%. Sitar et al. (1999) stated that sea lampreys were the dominant source of mortality in the central and southern main basins of Lake Huron. Sitar (1996) projected that numbers of age-

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