J. Res. 29 (Supplement 1):655–676 Internat. Assoc. Great Lakes Res., 2003

Sea Control in

J. Ellen Marsden1,*, Brian D. Chipman2, Lawrence J. Nashett3, Jon K. Anderson2, Wayne Bouffard4, Lance Durfey3, John E. Gersmehl4,5, William F. Schoch3, Nicholas R. Staats4, and Adam Zerrenner1,6 1School of Natural Resources Aiken Center, University of Vermont Burlington, Vermont 05401 2Vermont Department of and Wildlife 111 West Street Essex Junction, Vermont 05452 3New York State Department of Environmental Conservation Bureau of Fisheries Route 86, P.O. Box 296 Ray Brook, 12977-0296 4U.S. Fish and Wildlife Service Lake Champlain Fish and Wildlife Resources Office 11 Lincoln Street Essex Junction, Vermont 05452

ABSTRACT. In 1990, the United States Fish and Wildlife Service (USFWS) and state agencies initi- ated an 8-year experimental sea lamprey (Petromyzon marinus) control program on Lake Champlain to reduce parasitic phase sea lamprey and increase sport fish survival and growth. Twenty-four 3-tri- fluoromethyl-4-nitrophenol (TFM) treatments were conducted on 13 tributary systems, and nine Bay- luscide treatments were conducted on five deltas. Most tributaries received two rounds of treatment, 4 years apart. Trap catches of spawning-phase sea lamprey in three monitored tributaries declined by 80–90% from 1989 to 1997, but nest counts were reduced by only 57% during the same period. Sixteen of 24 TFM treatments reduced ammocoetes to less than 10% of pre-treatment levels. Eight of nine Bay- luscide treatments resulted in mean ammocoete mortality rates over 85% in caged test . Non- target effects were noted among amphibians, mollusks, macroinvertebrates, native lamprey, and other , and were higher for Bayluscide treatments than TFM. Recovery of delta taxa occurred within 4 years after treatment. Wounding rates on and Atlantic salmon were reduced in the Main Lake basin. Catches-per-unit-effort (CPUE) and estimated angler catch of lake trout increased. A mod- erate (25%), statistically significant increase in survival of 3–4 yr lake trout was noted. Returns of Atlantic salmon (Salmo salar) to tributaries increased significantly after treatment, and there was an estimated 3-fold increase in returns to the Main Lake sport fishery. Angler catches of brown (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) were higher in 1997 than in 1990. Economic analysis of the program indicated a 3.5:1 economic benefit: cost ratio. Results indicate that the experimental control program was successful, and provide justification for continuing sea lamprey control on Lake Champlain. INDEX WORDS: Sea lamprey, control, TFM, Bayluscide, economic analysis, Lake Champlain.

*Corresponding author. E-mail: [email protected] 5Current address: 267 Belair Dr., Colchester, Vermont 05446 6Current address: Sacramento Fish and Wildlife Office, U.S. Fish and Wildlife Service, 2800 Cottage Way, Suite W-2605, Sacramento, Cali- fornia 95825

655 656 Marsden et al.

INTRODUCTION Sea lamprey (Petromyzon marinus) control in the Laurentian lakes was most recently initiated in Lake Champlain. In common with most of the Great Lakes, native salmonid populations (lake trout Salvelinus namaycush and landlocked Atlantic salmon Salmo salar) in Lake Champlain have been extirpated. These species are now supported by stocking, though limited natural reproduction by both species has been documented. A fishery for two exotic salmonids, rainbow trout (Oncorhynchus mykiss) and (Salmo trutta), was estab- lished in the mid 1970s and is also supported by stocking. Lamprey control was judged to be neces- sary to achieve fisheries management objectives and improve the economic benefits from sport fish- ing. An experimental sea lamprey control program (ESLCP) was initiated in 1990 to reduce parasitic phase sea lamprey abundance, assess effects of the reduction on the sport fishery and economics of the region, and to facilitate formulation of long-range policies and management strategies. This paper documents the results of the control program, the current status of sea lamprey in Lake Champlain, and discusses options for future control.

LAKE CHAMPLAIN Lake Champlain is a long, narrow lake, approxi- mately 200 km long and 21 km wide with an area of 1,130 km2, that lies between New York and Ver- mont and extends northward into Quebec (Fig. 1). The fish fauna is similar to that of the Great Lakes: coregonid species are limited to (Coregonus clupeaformis) and lake herring (C. artedi), and major forage for piscivores are native rainbow smelt (Osmerus mordax) and yellow perch (Perca flavescens). The predator population is dom- inated by the four salmonids and walleye (Stizoste- dion vitreum). Historic commercial fishing for lake trout was limited, and there is currently no tradi- tional commercial fishery on the lake. The origin of sea lamprey in Lake Champlain has FIG. 1. The Lake Champlain drainage basin, long been a topic of debate. A number of re- showing lake basins, lake management zones, and searchers, most recently Lawrie (1970) and Daniels tributaries mentioned in the text. Tributaries that (2001), suggest that sea lamprey are native to Lake were treated with TFM are underlined; deltas Ontario, the , and Lake Champlain, treated with Bayluscide are indicated by small tri- based largely on the absence of effective barriers to angles. block their migration into these lakes. Sea lamprey could have gained access to the lake from the St. Lawrence River via the Richelieu River, or may have entered more recently from the Hudson River via the Champlain Canal, opened in 1823, or from Sea Lamprey Control in Lake Champlain 657 the Richelieu River via the Chambly Canal, opened in 1843 (Lawrie 1970, Smith 1972). The first records of lamprey in the lake date from 1841 (Hal- non 1963), but the species identity is uncertain; a later survey of fish species in Lake Champlain in 1894 did not include sea lamprey, but by 1929 they were reported to be moderately common (Ever- mann and Kendal 1902, Greeley 1930).

SALMONIDS IN LAKE CHAMPLAIN It is uncertain whether sea lamprey were a factor in the decline of lake trout and Atlantic salmon populations in Lake Champlain. Both species were over-harvested during the 1800s, and Atlantic FIG. 2. Numbers of yearling-equivalent lake salmon reproduction was adversely affected by con- trout stocked into Lake Champlain by year class struction of dams (Plosila and Anderson 1985). and strain, 1972–1997. “Finger Lakes” represents Lake trout populations were considered to be ex- Seneca Lake strain, and also includes composite tinct by the late 1800s. No lake trout were found in strains of progeny from feral lake trout in lakes lakewide surveys in 1928 and 1953–4 (Anderson Ontario and Champlain, which were assumed to 1978). Early stocking attempts were made in be largely of Seneca Lake origin. “Other strains” 1894–1896, and again in 1958 and for several years include Jenny Lake, , Lake Supe- thereafter, but these efforts failed to produce a pop- rior (Marquette), Manitoba (Clearwater), Adiron- ulation of lake trout in the lake (Halnon 1963). A dack (Raquette Lake, Lake George), and Maine coordinated stocking program began in 1973. Strain (Allagash Lake). composition and ages of stocked lake trout were standardized with the 1988 year class and focused on yearlings, primarily from Seneca Lake strain and egg take from feral Lake Champlain lake trout. Experimental Sea Lamprey Control Program Lake trout are stocked annually in the Main Lake Joint efforts to restore fisheries in Lake Cham- only; limited stocking occurred in 1972 and plain began in 1973 with the formation of the Lake 1975–1977 in Malletts Bay and the Inland Sea, but Champlain Fish and Wildlife Management Cooper- was discontinued due to poor catches of adults. Be- ative (“Cooperative” herein), composed of the U. S. tween 39,000 and 341,000 lake trout have been Fish and Wildlife Service (USFWS), Vermont De- stocked annually since 1973 (Fig. 2). partment of Fish and Wildlife (VTDFW), and the Sporadic Atlantic stocking began in 1962 (unpubl. New York State Department of Environmental Con- data). Stocking of rainbow trout began in 1972, and servation (NYSDEC). The Cooperative developed of brown trout in 1977 (Fisheries Technical Commit- A Strategic Plan for the Development of Salmonid tee 1999). With the implementation of sea lamprey Fisheries in Lake Champlain in 1977 (Fisheries control, total annual stocking of all species combined Technical Committee 1977), with specific, measur- was limited initially to 690,000 yearling equivalents able objectives to re-establish a lake trout and At- lakewide. Managers were concerned that increased lantic salmon fishery, establish a rainbow trout survival and growth of lake trout as a result of sea fishery, and maintain the existing harvest of rain- lamprey control would lead to increased predation on bow smelt. It became apparent that sea lamprey rainbow smelt, potentially causing a decline in the control would be needed in order to achieve these primary salmonid forage base (LaBar 1993). Accord- objectives (Gersmehl and Baren 1985, Plosila and ingly, the total number of all salmonids stocked each Anderson 1985). For example, summer gillnetting year was reduced by up to 24% beginning with the data revealed a wounding rate (type AI–AIII 1994 year-class. This reduction did not affect evalua- wounds) for lake trout > 635 mm in the Main Lake tion of the ESLCP because fish stocked at reduced (zones 3A-3C) that varied from 87 to 100%, with a numbers (primarily lake trout) were not recruited mean number of up to 11 attack marks per lake into the sport fishery or sampling gear prior to the trout > 635 mm prior to control. end of the evaluation period. The Cooperative initiated an eight-year experi- 658 Marsden et al. mental program of sea lamprey control in 1990. The was not treated because water quality at the time program was based heavily on the use of two chem- may have resulted in an unacceptably high non-tar- ical lampricides, 3-trifluoromethyl-4-nitrophenol get fish kill, and uncertainty regarding apparent (TFM) and Bayluscide 5% granular (Bayluscide). contribution of these streams to the parasitic phase Evaluation of the program’s success was based on population did not warrant pursuit of international 30 criteria relating to sea lamprey reduction, sport permitting for the purposes of the ESLCP. Seven- fishery response, and forage fish assessment (En- teen additional tributaries were surveyed using gstrom-Heg et al. 1990, Fisheries Technical Com- electrofishing or Bayluscide and did not contain sea mittee 1999). lamprey; additional tributaries in the Lake Cham- Use of federal funding for the ESLCP required plain basin were classified as unsuitable for sea the preparation of an Environmental Impact State- lamprey and were not surveyed. ment (EIS) and the appropriate public processes as- sociated with the National Environmental Policy Control Methods Act (NEPA). Permits for sea lamprey control were obtained from both states. State-listed endangered TFM and threatened species addressed by these permits Two rounds of treatments were scheduled for included species which could potentially be threat- each of the 13 tributary systems with a 4-year inter- ened by lampricide treatments in certain streams, val between treatments (Table 1). Second treat- such as northern ( fos- ments of Stone Bridge Brook and Beaver Brook sor—endangered in Vermont), American brook were not needed due to absence of sea lamprey or lamprey ( appendix—threatened in low sea lamprey recolonization. The first (1991) Vermont), lake sturgeon (Acipenser fulvescens— treatment of Trout Brook was canceled because per- endangered in Vermont), eastern sand darter mit conditions regarding the capture and holding of (Ammocrypta pellucida—threatened in New York American brook lamprey outside of the treated and Vermont), channel darter (Percina copelandi)– reach could not be met. A decision not to treat the proposed for listing as endangered in Vermont), and Saranac River in 1996 was made due to flood-re- six unionid mussel species listed as threatened or lated scouring that reduced ammocoete habitat, and endangered, or proposed for listing in Vermont. The to the low estimated kill that occurred during the species proposed for listing in Vermont during the first treatment and high costs associated with treat- ESLCP are now officially listed. ing the river. Generally, TFM dosages used in New York were based upon a minimum lethal concentra- Pre-control Assessment of Sea Lamprey tion (MLC) established by on-site toxicity test, multiplied by a factor of 1.5 or lower. In Vermont, Prior to initiation of the ESLCP on Lake Cham- dosage was based on the lower of the MLC values plain, an assessment of sea lamprey distribution determined by toxicity test, or using prediction was conducted to locate and prioritize streams for charts, based on pH and alkalinity and multiplied treatment and to provide data for evaluating success by similar factors (Bills et al. 2003). The duration of the control program (Gersmehl and Baren 1985). of primary applications was usually 12 hours in Thirteen sea lamprey producing tributary systems streams in both states. and five deltas were given priority for treatment based on ammocoete catch-per-unit-effort (CPUE) in streams sampled with electrofishing gear and Bayluscide ammocoete density on deltas sampled with Baylus- Bayluscide (5% granular) formulation, applied at cide (Fig. 1). The Poultney River and its tributary, a rate of 100 pounds per acre, was utilized for lim- the Hubbardton River, were treated and assessed as ited larval surveys in estuarine and lentic environ- separate streams, so results from the two rivers will ments and for the treatment of deltas on the New be reported separately here. Five additional stream York side of the lake (Table 1). Similar surveys in- systems which contained sea lamprey were not des- dicated that sea lamprey were not present in delta ignated for treatment due either to low ammocoete areas of Vermont tributaries. Five deltas were densities (Youngman Brook, Winooski River/ Sun- treated in 1991, and four of these were treated again derland Brook, Missisquoi River), or presence of in 1995. The Little Ausable River delta did not re- (Malletts Brook/Indian ceive a second treatment in 1995 due to a lack of re- Brook). The Pike River/Morpion Stream system colonization. Sea Lamprey Control in Lake Champlain 659

TABLE 1. Schedule of TFM and Bayluscide treatments of tributary streams and deltas in the Lake Champlain basin, with stream discharge data (m3/sec), length (km) or surface area (ha) of treatment, and amount of active ingredient of each chemical used. Stream discharge data were measured during TFM treatments. TFM and Bayluscide are reported as kg of active ingredient. Years Discharge Km/area (ha) TFM Bayluscide treated (m3/sec) treated (kg) (kg) TFM Boquet R., NY 1990 4.81 4.2 380 0 1994 1.98 4.2 255 0 Little Ausable R., NY 1990 0.48 9.8 100 0 1994 0.42 9.8 125 0 Ausable R., NY 1990 7.50 10.5a 560 0 1994 9.20 10.5a 578 0 Salmon R., NY 1990 0.71 6.4 120 0 1994 0.42 6.4 70 0 Beaver Br., NY 1990 0.03 1.6 6 0 Putnam Cr., NY 1990 0.42 7.7 98 0 1994 0.17 7.7 99 0 Lewis Cr., VT 1990 0.96 15.1 345 0 1994 0.59 8.4 150 0 Stone Bridge Br., VT 1991 0.04 4.7 28 0 Mount Hope Br., NY 1991 0.20 2.1 30 0 1995 0.07 2.1 17 0 Trout Br., VT 1995 0.02 0.6 5 0 Poultney R., VT/NY 1992 4.81 16.9 360 0 1996 4.25 16.9 542 0 Hubbarton R., VT* 1992 0.54 3.2 70 0 1996 0.57 0.6 75 0 Saranac R., NY 1992 9.62 5.3 811 0 Great Chazy R., NY 1992 1.13 33.1 386 0 1996 3.28 33.1 768 0 Bayluscide Boquet R. delta, NY 1991 — 85.0 0 477 1995 85.0 0 477 Little Ausable R. delta, NY 1991 — 21.9 0 123 Ausable R. delta, NY 1991 — 66.8 0 375 1995 73.7 0 414 Salmon R. delta, NY 1991 — 21.9 0 123 1995 21.9 0 123 Saranac R. delta, NY 1991 — 62.4 0 350 1995 55.5 0 311 aincludes 0.8 km of tributary Dry Mill Brook. *tributary to Poultney River

Barriers ered to be a complete control alternative, as exten- Prior to the ESLCP, preliminary studies to exam- sive sea lamprey spawning habitat existed below ine the feasibility of lamprey barriers were con- both barriers. ducted on 15 rivers (Anderson et al. 1985). The authors concluded that it may be feasible to design Assessment of the and construct effective barriers on 11 of the 15 trib- Sea Lamprey Control Program utaries. Two pre-existing low-head dams, on the Great Chazy River, NY, and Lewis Creek, VT, were Spawning Phase Sea Lamprey Assessments reconstructed during the ESLCP to block spawning Spawning phase sea lamprey were monitored by runs. However, neither of these dams was consid- trapping with portable assessment traps (PATs); all 660 Marsden et al.

TABLE 2. Numbers of sea lamprey collected with portable assessment traps (PATs) from three Lake Champlain tributaries from 1982 to 1997. Sea lamprey were collected from Great Chazy River using a permanent trap beginning in 1995, with higher capture effectiveness than PATs; totals do not include sea lamprey from Great Chazy River. Stone Bridge Indian Lewis Great Year Brook Brook Creek Chazy River Total 1982 NA NA 149 NA 1983 NA NA 517 NA 1984 NA NA 670 NA 1985 NA NA 848 NA 1986 NA NA 600 NA 1987 NA NA 268 NA 1988 NA NA 224 NA 1989 108 61 596 NA 765 1990 350 410 489 NA 1,249 1991 91 184 219 NA 494 1992 16 93 231 NA 340 1993 12 59 234 234 305 1994 10 83 421 NA 514 1995 13 125 109 1,023 247 1996 8 80 59 1,236 147 1997 2 8 58 223 68 sea lampreys collected in the traps were removed for the majority of the overall reduction in nesting from the stream. Three streams were monitored lakewide. throughout the experimental program; Lewis Creek, starting in 1982, and Indian Brook and Stone Larval Phase Assessments Bridge Brook starting in 1989. In each stream, catch dropped below 10% of pre-control levels by Pre-control larval sea lamprey assessments using the end of the control program (Table 2). Indirect electrofishing CPUE were used to identify and se- indices of population size, weight, and sex ratio lect streams for treatment (Gersmehl and Baren were also monitored during the spawning season. 1985). Production estimates of larval phase sea The sex ratio of spawning sea lamprey captured lamprey were not determined for Lake Champlain with PATs shifted toward a higher proportion of fe- tributary streams during the ESLCP. The Great males, but the difference was not statistically sig- Lakes Fishery Commission (GLFC) Quantitative nificant (t-test, p > 0.05). Average weight of spawning sea lamprey did show a significant in- crease (t-test, p < 0.001) in Lewis Creek (Fisheries Technical Committee 1999). Nest counts were conducted annually on ten trib- utaries in index sections to monitor spawning activ- ity throughout the basin. There was an overall reduction in nests to 42.6% of the pre-control (1983-1991) average (Fig. 3). The evaluation crite- rion for successful treatment called for a reduction in the numbers of sea lamprey nests tallied at index sites to 20% of pre-control values. This criterion was not met on either a lakewide basis or in indi- vidual streams except in the Great Chazy River, where a dam was reestablished as a sea lamprey barrier below the index section. This reduction in FIG. 3. Total sea lamprey nests counted in 10 spawning in the Great Chazy River also accounted tributaries of Lake Champlain, 1983 to 1997. Sea Lamprey Control in Lake Champlain 661

TABLE 3. Summary of sea lamprey mortality and number of transformers estimated post-treatment on Lake Champlain tributaries. Percent sea lamprey < 100 reflects the presence of native lamprey species in tributaries. The numbers of sea lamprey transformers were derived by multiplying the proportion of trans- formers in samples collected by mortality survey crews by the number of all lamprey mortalities observed. Mortality counts are conservative indicators, and likely underestimate mortality in all streams. Sea lamprey Treatment mortality Percent sea Number of Percent River Year count lamprey transformers transformers 1990 64,828 99.96 12,976 20.0 1994 63,648 99.94 71 0.1 Little Ausable River 1990 122,456 99.94 31,411 25.7 1994 38,274 99.52 631 1.7 Ausable River 1990 24,506 66.78 2,310 9.4 1994 69,243 71.03 1,081 1.6 Boquet River 1990 6,325 99.40 1,197 18.9 1994 6,564 97.97 72 1.1 Beaver Brook 1990 1,005 98.14 131 13.0 Putnam Creek 1990 30,230 96.18 3,121 10.3 1994 20,659 98.05 1,114 5.4 Lewis Creek 1990 25,942 97.95 4,297 16.6 1994 41,408 92.81 871 2.1 Mount Hope Brook 1991 26,970 99.36 4,252 15.8 1995 11,308 99.87 1,433 12.7 Stone Bridge Brook 1991 545 70.9 277 50.8 Trout Brook 1995 157 63.3 75 47.8 Great Chazy River 1992 132,796 99.85 41,706 31.4 1996 22,712 99.95 395 1.7 Saranac River 1992 394 100 3 0.8 Poultney River 1992 197 66.11 0 0 1996 6,759 72.61 989 14.6 Hubbardton River 1992 182 100 8 4.4 1996 20 100 0 0

Assessment Survey (QAS) protocol (Slade et al. substrate characteristics, and consumption by scav- 2003) was used to evaluate larval populations in engers (Fisheries Technical Committee 1999). two Lake Champlain tributary systems in 1999 The effectiveness of TFM treatments was evalu- (Dean and Zerrenner 2000), and an additional two ated using ammocoete abundance (CPUE) data col- tributaries were evaluated in 2000. In the future, it lected at index stations before and after treatment. is anticipated that more stream surveys will be done The majority of electrofishing was done with a 250- using the QAS protocol. volt DC generator mounted in a canoe. AbP-2 back- pack electrofishing units (Slade et al. 2003) were used in instances where access was difficult and in Assessment of TFM Treatment Effectiveness streams too small to accommodate the canoe unit. Mortality resulting from TFM treatments was as- Electrofishing stations were selected throughout sessed following all treatments. Assessment crews stream reaches infested with sea lamprey in optimal waded or canoed in nearly all treated stream sec- habitat, and were used to monitor the sea lamprey tions and counted all visible dead ammocoetes, gen- population throughout the ESLCP. Stations were erally beginning 24 hr behind the leading edge of moved slightly in some instances to accommodate the TFM block (Table 3). Samples of dead ammo- changes in stream conditions such as water level coetes were also collected for later identification to and substrate changes. species. Counts were minimal estimates of mortal- A treatment was considered to be successful if ity, as accuracy was affected by field conditions post-treatment population densities at index sta- such as light, water clarity, vegetation, water depth, tions, as indicated by relative abundance estimates, 662 Marsden et al.

TABLE 4. Comparison of sea lamprey ammocoete catch rates before and after treatment of tributary streams between 1990 and 1996. CPUE refers to catch per unit effort equivalent to 30 min of electrofish- ing per standard-sized plot sampled.

Pre-treatment Post-treatment Percent survey results survey results overall Number of Total Total reduction in stations River year catch CPUE catch CPUE catch rates sampled Salmon River 1990 208 52.0 18 4.5 91.3 4 1994 1,050 87.5 21 1.75 98.0 12 Little Ausable River 1990 598 66.4 8 0.9 98.7 9 1994 684 85.5 16 1.5 95.7 11 Ausable River 1990 31 7.8 18 4.5 41.9 4 1994 469 67.0 2 0.3 99.5 7 Boquet River 1990 —a —a 99 12.4 —a 8 1994 170 24.3 25 3.6 81.0 7 Beaver Brook 1990 —a —a 20 20.0 —a 1 Putnam Creek 1990 198 66.0 14 4.6 92.9 3 1994 922 84.0 285 25.9 69.1 11 Lewis Creek 1990 169 56.3 15 5.0 91.1 3 1994 544 49.5 20 1.8 96.3 11 Mount Hope Brook 1991 101 101.0 34 34.0 66.3 1 1995 216 31.0 8 1.1 96.3 7 Stone Bridge Brook 1991 232 116.0 0 0 100 2 Trout Brook 1995 80 10.0 00100 8 Great Chazy River 1992 562 80.3 7 1.0 98.8 7 1996 561 80.1 0 0 100 7 Saranac River 1992 456 57.0 102 12.8 76.4 8 Poultney River 1992 248 13.0 286 15.0 –15.3 19 1996 459 23.0 20 1.0 95.6 20 Hubbardton River 1992 72 7.2 2 0.2 97.2 10 1996 18 1.0 1 0.125 94.4 8 aDue to flow conditions, pre-treatment surveys were not conducted in Beaver Brook and the Boquet River prior to the 1990 treatment.

did not exceed 10% of pre-treatment levels. This in 1992, the Poultney River was required to be evaluation criterion was met or exceeded in seven treated with a dose at 0.8 times the lower of the of the 11 streams evaluated after the first round of minimum lethal concentrations as determined from treatment, and nine of 11 streams treated in the sec- both a toxicity test and the predictive pH and alka- ond round (Table 4). The effectiveness of two treat- linity chart. This lowered target concentration was ments in 1990, on Beaver Brook and the Boquet due to concern over nontarget species presumed to River, could not be evaluated because high flow be sensitive to TFM, including the state-listed east- conditions prevented pre-treatment surveys (Fish- ern sand darter as well as several mussel species. eries Technical Committee 1999). Surviving ammo- Only 200 dead ammocoetes were counted after coetes tended to be larger on average than the mean treatment, and the post-treatment CPUE (15.1 am- length of ammocoetes in streams prior to control mocoetes/hr) was higher than pre-treatment and most residual ammocoetes sampled the year (13.1/hr). Modified permit conditions allowed for after treatment were transformers. Low treatment the second treatment in 1996 to be conducted at 1.0 effectiveness was generally attributable to field times MLC as determined by bioassay, resulting in conditions unique to portions of the rivers, e.g., low approximately 7,000 mortalities and a drop in TFM movement in areas of low water flow or back- CPUE from 23.0/30 min to 1.0/30 min (Table 4). waters, or presence of ground-water infusion that Reestablishment of ammocoetes was documented was inferred based on local reduction of TFM con- within one to two years following treatment in all centration. Due to restrictive permitting conditions treated streams except Stone Bridge Brook and Sea Lamprey Control in Lake Champlain 663

Trout Brook. During the first scheduled TFM treat- quet River delta was 73%, and 2–6% of lamprey re- ment of Stone Bridge Brook in 1991, the stream re- covered from control cages were dead. Several ceived simultaneous treatments at two locations, cages were lost during assessment of the 1995 treat- resulting in increased exposure time in the lower ment; 100% mortality of the remaining ammocoetes reaches of the stream. The number of spawning occurred in the Boquet and Saranac river deltas, phase sea lamprey captured in Stone Bridge Brook 96% mortality occurred in the Ausable River delta, dropped from a high of 350 in 1990 to 16 in 1992 and 87% in the Salmon River delta. and continued to decline to a low of 2 animals in 1997. This decline in the number of spawning Assessment of Effects on Nontarget Species adults and the lack of recolonization may be attrib- uted to a very effective treatment in 1991 and sub- The Cooperative collected routine nontarget sequent effective spawning-phase assessment mortality data from each stream and delta after trapping operations. Trout Brook was treated in treatment. Nontarget mortality was assessed simul- 1995 and no recolonization has been detected since taneously with sea lamprey mortality as described then. Very low levels of ammocoetes were detected above. Eleven additional studies were conducted in Beaver Brook and the Saranac River by the third that focused on species or areas of special concern year after treatment. (Fisheries Technical Committee 1999). Streams in which no sea lamprey were initially Estimates of the number of native lamprey killed found, but which have suitable sea lamprey habitat, by TFM treatments were obtained by counting each were periodically monitored during the ESLCP. species in larval subsamples and extrapolating to an Two streams which initially harbored no sea lam- entire stream. One stream segment on the Ausable prey populations were found to be infested during River was inaccessible for this survey, and one seg- the ESLCP. The LaPlatte River was first surveyed ment on the Great Chazy River was subsampled in 1992; in 1993 sea lamprey were found for the due to time constraints. Crews counted affected first time, and in 1997 sea lamprey and silver lam- fish, amphibians, and large invertebrates (crayfish prey (Ichthyomyzon unicuspis) were found. Sea and mussels) in the field, or preserved samples of lamprey were found in Mullen Brook in late 1991; unidentified species for later laboratory identifica- only American brook lamprey had been recorded in tion. Permit conditions required collection of all an earlier survey. dead amphibians in most New York streams. Growth rates of re-established ammocoetes were Mortality of American brook, silver and northern determined for eight rivers using length-frequency brook lamprey occurred after TFM treatments analysis in order to predict the age at which ammo- (Table 6). American brook lamprey had the highest coetes would begin metamorphosis. These data mortality of native lamprey for all streams; an esti- were important for predicting future treatment in- mated 40,851 individuals were killed in the Little tervals to ensure that no ammocoetes metamor- Ausable, Ausable, and Salmon rivers and Trout phosed prior to treatment. Growth rates ranged Brook during the two rounds of treatment. An esti- from a low of 15 mm/yr to a high of 45 mm/yr mated 8,619 were killed in seven (Table 5). Predicted age for metamorphosis was 4+ streams, and an estimated 209 northern brook lam- to 5+ in most streams. Estimated growth rates in the prey were killed in the Great Chazy River. Mortal- Poultney River and Lewis Creek indicated that ity of native lamprey was greater after the second metamorphosis could occur after 3 years of stream round of stream treatments than the first, except for growth. silver lamprey in Mt. Hope Brook and northern brook lamprey in the Great Chazy River, suggesting that individuals survived in or recolonized the treat- Assessment of Bayluscide Treatment Effectiveness ment areas. Effectiveness of delta treatments was evaluated Mortality of nontarget lamprey after Bayluscide using ammocoetes in live cages in each of the five application was qualitatively estimated by walking treated deltas. Up to four cages with 20 ammo- along the shoreline and counting dead lamprey. coetes each were placed in the treatment zones and American brook lamprey were the only nontarget control cages were placed outside the treatment lamprey observed to be affected by Bayluscide; zone. Treatments in 1991 on four of the deltas re- 1,267 dead individuals were collected on the Aus- sulted in 100% mortality of caged ammocoetes and able and Salmon river deltas. Mortality on both no mortality in control cages; mortality in the Bo- deltas was higher after the second treatment than 664 Marsden et al.

TABLE 5. Year-class, age, mean length (mm), and growth rates (during preceding year) at the end of the November growing season of re-established sea lamprey ammocoetes following TFM treatments (*indi- cates a treatment). The first length listed for each river is the minimum length of transformers measured pre-treatment. 1990* 1991 1992 1993 1994* 1995 1996 1997 Age 0+ 1+ 2+ 3+ 0+ 1+ 2+ Salmon River N 171 144 1148 481 4 131 269 Mean size 120 33 64 90 115 33 65 93 Growth rates (mm/yr) 31 26 25 32 28 Ausable River N 52 125 389 166 25 9 40 Mean size 127 40 64 101 117 35 80 105 Growth rates (mm/yr) 24 37 16 45 25 Little Ausable River N 11616821,27310NA12 Mean size 127 27 62 89 111 37 62 84 Growth rates (mm/yr) 35 27 22 25 22 Lewis Creek N 103 149 382 3,329 Mean size 126 42 80 102 122 Growth rates (mm/yr) 38 22 20 Putnam Creek N 24 75 450 46 50 28 165 Mean size 130 27 59 83 112 30 66 92 Growth rates (mm/yr) 32 24 29 36 26 Boquet River N 3348497429 Mean size 133 30 55 84 112 Growth rates (mm/yr) 25 29 28

1992* 1993 1994 1995 1996* Age 0+ 1+ 2+ 3+ Poultney River N 10 85 145 361 Mean size 120 38 78 104 135 Growth rates (mm/yr) 41 26 31 Great Chazy R. N 14 43 314 523 Mean size 135 33 58 93 108 Growth rates (mm/yr) 25 35 15 the first, indicating either an incomplete kill or re- species in any single treatment event, and an aver- colonization after the first treatment. Mortality of age of 2.8 or fewer mortalities per species per treat- this species was unexpected, as pre-control surveys ment. For nine fish species there were one or more had not detected American brook lamprey in deltas, treatments with more than 50 mortalities per and this species is generally assumed to live en- species. Mortality was observed among eleven tirely within stream habitats. groups of invertebrates and amphibians after TFM Excluding native lamprey, TFM mortality was treatments. Tadpoles (Rana spp.), salamanders (not associated with 47 identifiable fish species. For 38 identified to species), red spotted newts (Notoph- species there were fewer than 50 mortalities per thalmus viridescens), and mudpuppies (Necturus Sea Lamprey Control in Lake Champlain 665

TABLE 6. Mortality counts for nontarget species associated with 24 TFM treatments of Lake Cham- plain tributaries. Observed mortalities in the two years of treatment are listed sequentially for any species and river in which at least one treatment mortality count was greater than 50. Numbers of native lamprey are estimates derived from sub-samples. Total # treatments with Taxa Species, rivers with mortality > 50 mortality > 50 mortalities Lampreys American brook lamprey (Lampetra appendix) 40,851 5 Ausable R. (12,193, 28,245), Little Ausable R. (74,184) Trout Br. (92) silver lamprey (Ichthyomyzon unicuspis) 8,619 9 Stone Bridge Br. (224), Mt. Hope Br. (175, 15), Poultney R. (101, 2,549), Boquet R. (38, 136) Putnam Cr. (1,202, 410) Lewis Cr. (543, 3,207) northern brook lamprey (Ichthyomyzon fossor) 209 1 Great Chazy R. (197, 12)

Teleost Fishes stonecat (Noturus flavus) 6,730 6 Little Ausable R. (21, 196), Salmon R. (141,185), Saranac R. (331), Great Chazy R. (5,768, 88) log perch (Percina caprodes) 1,057 3 Ausable R. (9, 82), Lewis Cr. (248, 26), Great Chazy R. (561, 28) bluntnose minnow (Pimephales notatus) 755 1 Stone Bridge Br. (725) blacknose dace (Rhinichthes atratulus) 517 2 Putnam Cr. (8, 424), Lewis Cr. (66, 0) white sucker (Catostomus commersoni) 340 2 Stone Bridge Br. (170), Mt. Hope Br. (2, 75) tessellated darter (Etheostoma olmstedi) 318 2 Lewis Cr. (114, 4), Stone Bridge Br. (64) brown bullhead (Ameiurus nebulosus) 277 1 Lewis Cr. (18, 121) chain pickerel (Esox niger) 130 1 Mount Hope Br. (78, 19) longnose dace (Rhinichthyes cataractae) 66 1 Lewis Cr. (53, 2) other species combined (38) 451 0

Amphibians, invertebrates Frog tadpole (Rana spp.) 5,461 3 Stone Bridge Br. (364), Great Chazy R. (1,460, 3,614) Mudpuppy (Necturus maculosus) and unidentified salamander 1,923 3 Putnam Cr. (3, 90), Great Chazy (1,209, 442) Red-spotted newt (Notophthalmus viridescens) 362 2 Mt. Hope Br. (295, 67) Crayfish (Orconectes spp.) 36 0 Frog adult (Rana spp.) 33 0 Two-lined salamander (Eurycea bislineata) 41 0 Unidentified mussel 25 0 Leopard frog (Rana pipiens)10 Leech (Hirudinea) 10 Unid. worm 1 0 666 Marsden et al.

maculosus) had the highest levels of mortality Bayluscide treatment of the Little Ausable River (Table 6). Most species for which mortality oc- delta in four of eight macroinvertebrate orders: curred in the first treatment were detected again in Gastropoda, Pelecypoda, Diptera (chironomids), similar numbers after the second round of treat- and Hirundinea (Gruendling and Bogucki 1993b). ment, which suggests survival or recolonization One year later, Hirudinea, Gastropoda, and Pelecy- after the first treatment. poda remained significantly below pre-treatment Bayluscide treatments caused mortality of 29 densities (Wilcoxon Rank Sum Test, p < 0.05). identifiable fish species. Mortality was minimal for Gastropoda, Pelecypoda, Oligochaeta, Hirudinea, most species except for banded killifish (Fundulus and Diptera declined in density (Wilcoxon Rank diaphanus), mimic shiner (Notropis volucellus), Sum Test, p < 0.005) in the Ausable River delta spottail shiner (N. hudsonius), yellow perch, emer- after Bayluscide treatment, but no significant ald shiner (N. atherinoides), and white sucker change was seen in Amphipoda, Isopoda, or (Catostomus commersoni); of the nine treatments, Ephemeroptera. A year later, Diptera, Gastropoda, six treatments resulted in observed mortality of > and Pelecypoda remained below pre-treatment den- 50 of one or more of these species. In addition, sities (Wilcoxon Rank Sum Test, p < 0.001; Gru- mortality of 32 mussels, 2 crayfish, 2 snails, and 1 endling and Bogucki 1993b). However, 4 years frog tadpole was observed (Fisheries Technical after the 1991 Bayluscide treatment of the Little Committee 1999). Ausable and Ausable deltas, mussel and gastropod The effect of TFM treatment on eastern sand densities had recovered to pre-treatment levels darters was assessed in situ using 91 individuals (Lyttle 1996). Hirudinea and Diptera were not re- held in cages in stream sections exposed to TFM assessed. and upstream in a control site during the 1990 and Native mussels were monitored in the Poultney 1994 Lewis Creek treatments. No mortalities oc- River and Little Ausable and Ausable River deltas. curred during the 1990 treatment, and two mortali- No stress (gaping, loss of orientation or filtering ac- ties, possibly unrelated to treatments, were tivity) was noted among 10 mussel species in beds documented among 24 darters held within the TFM during the 1992 Poultney River treatment (Fichtel block in 1994 (MacKenzie 1991, 1995). Caged east- 1992). Gravid mussels held within the Poultney ern sand darters were also held in situ during the River treatment area did not prematurely release 1992 and 1996 TFM treatments of the Poultney River; no mortalities occurred. glochidia during and for at least five days after the Short-term and long-term effects of TFM on fish 1996 treatment, and no glochidia were found in and invertebrates were monitored in Lewis Creek, drift net samples below the TFM application point Trout Brook, and the Little Ausable and Ausable (Lyttle and Pitts 1997). No statistically significant River deltas. Community level analysis of Lewis mortality occurred in mussels held in cages on the Creek showed no adverse effects on macroinverte- Little Ausable and Ausable River deltas during brates, including pollution-sensitive and TFM-sen- TFM treatment of their respective rivers; four of sitive species, after TFM treatments (Langdon and 180 caged unionids died (Gruendling and Bogucki Fiske 1991, VTDEC 1994). Density, species rich- 1993a). High mortality of eastern elliptio (Elliptio ness, and EPT (Ephemeroptera, Plecoptera, and Tri- complanata; 9.1–70%) and eastern lampmussel choptera) Index were slightly greater post-treatment (Lampsilis radiata; 52.5–94%) occurred in cages in Trout Brook, though the difference was not sta- during Bayluscide treatment of Little Ausable and tistically significant (Mann-Whitney U Rank Sum Ausable River deltas, whereas no mortality oc- test, p > 0.05; VTDEC 1996). A modified Index of curred in controls located outside the treatment area Biotic Integrity applied to fish species showed iden- (Gruendling and Bogucki 1993b; Table 7). Density tical scores before and after treatment, though of Lampsilis radiata and Elliptio complanata after abundance of individual species did change after treatment on both deltas was less than pre-treatment treatment (VTDEC 1996). Community sampling of (Wilcoxon Rank Sum Test, p < 0.001); neither invertebrates in the Little Ausable and Ausable species reached pre-treatment density after 1 year. River deltas showed no significant differences be- Laboratory studies estimated a 24 hr LC50 of 998 tween pre-and post-treatment using TFM (Gru- ng/L of Bayluscide for E. complanata, and 178 endling and Bogucki 1993a). ng/L for L. radiata (Gruendling and Bogucki Statistically significant (Wilcoxon Rank Sum 1993b). The highest mean concentration achieved test, p < 0.001) declines in density occurred after within a 24 hr period after treatment was 298.2 Sea Lamprey Control in Lake Champlain 667

TABLE 7. Mean percent mortality of unionid mussels in cage experiments and ambient conditions in two deltas treated with Bayluscide. Ten replicates of cages and field plots were measured in the Little Ausable River, and 11 each in the Ausable River. ND = no data. Caged Field Plots NMeanSD N MeanSD Little Ausable River Elliptio complanata 100 70.0 34.3 202 42.0 25.2 control 10 0 0 ND

Lampsilis radiata 100 94.0 8.4 56 80.9 26.2 control 10 0 0 ND

Ausable River Elliptio complanata 110 32.7 32.0 33 10.8 18.2 control 10 0 ND

Lampsilis radiata 110 73.6 33.2 387 62.8 26.1 control 10 0 ND ng/L on the Little Ausable River and 167.7 ng/L on the primary lake trout range (Fig. 4). CPUE outside the Ausable River. zones 3A and 3B also increased, from a mean of 1.77 (± 0.295, 90% confidence interval) lake trout Salmonid Wounding and Survival per net lift pre-treatment (1982–1990) to a mean of 3.96 (± 0.375, 90% confidence interval) post-treat- Lake Trout ment (1991–1997). This difference was statistically Intensive gill-netting of lake trout was conducted significant using a nonparametric Mann-Whitney from 1982 to 1997 to collect CPUE data as an index test (p ≤ 0.000). In open water creel surveys, total of abundance. Assessment gillnets were 1.8 m deep, catch increased 76% from an estimated 23,345 122 m long, with eight 15-m panels of multifila- (± 3,270, 90% confidence interval) in 1990 to ment nylon ranging (in sequence) from 6.4 to 15.3 41,162 (± 4,999, 90% confidence interval) in 1997, cm stretch mesh in 1.3 cm increments. Use of accompanied by no significant change in fishing ef- spreader bars, float lines versus floats, old versus fort. Average weight of lake trout increased by 7% new nets, and types of leads varied between states over the same period. The proportion of lake trout and among years, leading to possible variation in > 635 mm in the harvest increased by 42%. catch rates. Nets were set between June and August, Survival estimates were calculated based on primarily in the Main Lake (zones 3A and 3B; Fig. CPUE data that had been corrected for gill net se- 1), though sampling also occurred in zones 2B, 2C, lectivity, swimming speed, and probability of cap- 3C, 4A, 4B, 5A, 5B, and 5C. Lake trout were mea- ture by means other than gilling (Fisheries sured (TL) and weighed on board, and lamprey Technical Committee 1999). Selectivity curves wounds and scars were recorded using standard cri- were developed for each pair of mesh sizes, assum- teria (King and Edsall 1979). Lake trout in Lake ing that probabilities of capture for a given mesh Champlain were marked with one of five fin clips are normally distributed around an optimum fish in a five year-rotation, so that ages of captured fish length for that mesh (Holt 1963, Fisheries Technical could be determined using a combination of length- Committee 1999). The selectivity curves were ad- frequency analysis and fin clip information; scales justed to account for the tendency for larger fish to were read when these data were in doubt. Length- have high probabilities of encountering gill nets be- frequency and clip data were deemed to be reliable cause of their faster swimming speed and greater methods for aging up to at least age 6. foraging range (Rudstam et al. 1985). The resulting CPUE of lake trout in assessment gillnets in- selectivity curves were used to correct data from all creased over the study period in zones 3A and 3B, years and both states’ gill netting. Extraordinarily 668 Marsden et al.

FIG. 4. Catch-per-unit-effort (net lifts) of lake trout in zones 3A and 3B in Lake Champlain from 1982 to 1997. Bars represent a 95% confidence interval. N refers to the number of net lifts. high catches in 1984 and 1996 were considered to set. The small number of year classes in the post- be anomalies, and the CPUE data for these years control data set limits these survival estimates, so were derived by running two linear regressions, the data were re-analyzed by netting year. After using pre-control CPUE data (1982 to 1990) for weighting age 3 fish to a uniform number to reduce 1984, and using post-control CPUE data (1991– the effect of highly variable survival from stocking 1997) for 1996. to age 3, netting year survival estimates yielded The truncated Chapman-Robson method was similar results to year-class survival estimates, ex- used to estimate survival rates of individual year cept that age 5–9 survival increased significantly in classes for age 3–6 and 4–9, and the Heincke esti- netting-year analysis (Table 8). Number of year mate was used for age 3–4 (Fisheries Technical classes of lake trout present in the lake increased Committee 1999). Lake trout younger than age 3 from eight in 1982 to 12 in 1997. There was a sig- were eliminated from the survival estimates be- nificant decrease in length-at-age from the pre- cause these fish were not fully vulnerable to the gill treatment to the post-treatment period (1982–90 vs. nets. Non-Seneca Lake strain lake trout were also 1991–97) for seven of the eight year classes ana- excluded where possible to eliminate the potential lyzed (t-test, p < 0.05); there was also a significant bias from a greater preponderance of non-Seneca decrease in length-at-age during the pre-treatment Lake strain lake trout stocked in earlier years. Sur- period (1982–85 vs. 1986–90) for ages 5 through 10 vival estimates by year class of lake trout from age (t-test, p < 0.05). 3 to age 4 increased from 0.35 pre-control to 0.44 Fishing mortality rates were estimated using post-control (p < 0.015); survival of age 3–6 lake tagged fish and creel surveys. Lake trout have been trout increased from 0.47 pre-control to 0.52 post- tagged annually since 1988 with anchor tags. Creel control (p < 0.069). Survival of age 5–9 lake trout surveys conducted in 1990, 1991, and 1997 gener- (0.57 pre-control) also did not change significantly ated sufficient data to estimate fishing mortality. (p < 0.301; Table 8); however, this comparison was Lake trout angler catch is limited to fish greater had only three year classes in the post-control data than 38 cm, up to three fish per day, year round. Sea Lamprey Control in Lake Champlain 669

TABLE 8. Survival estimates for lake trout before and after sea lamprey control in Lake Champlain. Data were compared using a one-tailed t-test. by year-class by netting year Age Period Interval Survival SD p-value Interval Survival SD p-value 3–4 pre-control 1979–87 0.35 0.07 1983–90 0.35 0.08 post-control 1988–93 0.44 0.06 0.015 1991–97 0.43 0.06 0.021

3–6 pre-control 1979–87 0.47 0.05 1985–90 0.47 0.05 post-control 1988–91 0.52 0.03 0.069 1991–97 0.51 0.03 0.037

5–9 pre-control 1979–85 0.57 0.03 1986–90 0.51 0.06 post-control 1986–88 0.58 0.01 0.301 1991–97 0.59 0.03 0.005

The estimated total number of fish harvested with significant post-control reduction in wounding and tags in the year following tagging was divided by scarring occurred in the three smallest size classes the number of fish tagged in the previous year. (p < 0.05). However, this analysis cannot account Using a tag loss rate of 0.26 estimated by Fabrizio for changes in sea lamprey prey selection as a result et al. (1996), fishing mortality was 0.14 in 1990, of changing predator/prey ratios during the period. 0.11 in 1991, and 0.14 in 1997. Creel surveys yielded annual mortality rate estimates from catch Other Salmonids curve analysis of 0.79 in 1990 (pre-control) and 0.30 to 0.39 in 1997 (post-control) for age 6-9 lake Survival of adult Atlantic salmon was assessed trout. As fishing mortality did not appear to change using the number of fish returning to the Saranac materially over the period of study, the changes in River sport fishery in fall creel surveys, passage at survival represent decreases in natural mortality. the Willsboro Fishway on the Boquet River, and by Collection of wounding and scarring data began fall electrofishing surveys conducted in the Inland in 1982. Wounds were evaluated as the sum of all Sea at Sandbar Bridge and the Lamoille River, trib- Type AI, AII, and AIII wounds combined; scars utary to Malletts Bay. Average returns of fish sam- were type AIV marks. Wounding and scarring was pled in the Saranac River and Willsboro Fishway relatively low (51 wounds and 102 scars per 100 increased in all size-classes, up to 4.8 times higher lake trout) in the early 1980s, and rose to a peak of in post-treatment relative to pre-treatment years 73 wounds per 100 lake trout in 1991 and 185 scars per 100 lake trout in 1992 (Fig. 5). Subsequent to inception of the control program, the wounding and scarring numbers returned to mid-1980s levels. An independent samples t-test was performed for wounds per lake trout and scars per lake trout for each size class and all size classes combined for pooled pre-treatment (1982–1991) and post-treat- ment (1992–1997) samples. There was a significant decrease in wounds and scars in comparisons of each individual size class (maximum p < 0.001), and when all size classes were combined (maxi- mum p < 0.022). Wounding and scarring rates were also examined by adjusting for the relative number of lamprey-vulnerable lake trout in the lake each year. Population estimates for each year were not FIG. 5. Sea lamprey wounding data for lake accurate because of highly variable recruitment of trout collected in zones 3A and 3B in Lake Cham- age-3 lake trout to the gill nets, so average catch- plain between 1982 and 1997. Wounds are the sum per-net-lift was used as a relative index of abun- of AI—AIII wounds. Vertical line indicates begin- dance. Analysis using this adjustment indicated that ning of control program. 670 Marsden et al.

TABLE 9. Returns of Atlantic salmon to letts Bay, and Inland Sea, but a decrease was seen Saranac River, as sampled in the fall creel survey in the Saranac River creel data. Numbers of larger, (estimated angler catch at age), the Willsboro fish- older fish reported caught in the Saranac River in- way, and the Lamoille River and Sandbar Bridge creased, but these increases were not reflected in sites sampled by electroshocking. Data for the nearshore electrofishing surveys and fish handled Willsboro fishway, Lamoille River, and Sandbar by creel agents during Saranac River spring creel Bridge are mean numbers of returns per year. surveys. age (lake-year) Sea lamprey wounding rates on rainbow trout, brown trout, and Atlantic salmon generally de- Site and year 1 2 3 4 creased between pre-control and post-control peri- Saranac River ods. Trends in the data are difficult to ascertain due 1991 80 16 8 0 to low and highly variable annual catches in each 1996 157 77 33 4 sample type (seasonal gillnets, electrofishing, creel, and fish passage facilities, or fishways), and paucity Willsboro fishway of data prior to and after control. 1988–92 10.3 7.0 0.1 0 1993–98 31.5 8.0 2.5 0 Post-treatment wounding rates for Atlantic salmon decreased between 40 and 74% among three Sandbar Bridge, Inland Sea size-classes returning to the Willsboro Fishway and 1987–1992 34.8 18.5 2.5 0 two size classes sampled during open water creel 1993–1997 81.6 14.8 1.2 0.6 surveys in the Main Lake (Table 10). Wounding rates among Atlantic salmon sampled by elec- Lamoille River, Malletts Bay trofishing in Malletts Bay and the Inland Sea did 1987–92 37.3 19.2 2.3 0 not show significant declines in wounding for any 1993–97 64.4 27.8 4.2 0.4 size-classes; in over half of the size-class compar- isons, wounding rates actually increased between 10 and 123% (Table 10). A decrease in wounding (Table 9). Returns of 1-lake-year salmon increased of 83% was observed in Winooski River spring-run 3.5-fold (based on median values) in the Inland rainbow trout for all size-classes combined, but Sea; 4-lake-year salmon were noted for the first could not be statistically evaluated because wound time after control, but returns of 2- and 3-lake-year data per individual fish were not available for the fish did not change substantially. Data on returns of pre-control data. Changes in wounding rates for salmon to the Lamoille River were difficult to inter- brown trout could not be evaluated due to small pret, due to dramatic annual changes in the river sample sizes. flow exacerbated by water retention for hydropower generation. Estimated catch of salmon in the Saranac River decreased (0.056% to 0.018% returns Cost/Benefit Analysis per smolt stocked) in spring creel surveys and in- The ESLCP generated estimated 1990 discounted creased (0.011% to 0.035%) in fall creel surveys. benefits of $29,379,211 and had discounted costs of Estimated returns per smolt stocked in the Main $8,447,011, resulting in a net benefit of Lake open water fishery increased from 0.52% to $20,902,200 or a benefit:cost ratio of 3.48:1 1.63%. There was little change in the condition fac- (Gilbert 1999a). Success of sea lamprey control in- tor for Atlantic salmon sampled throughout the duced members of an estimated 32,528 households lake. to increase their annual participation in water-based Angler harvest of rainbow trout in the Saranac recreation on Lake Champlain by 219,564 days dur- River was assessed as part of the evaluation pro- ing the 8-year period and spend an additional $8.8 gram, but did not demonstrate an increase in the million on these activities (Gilbert 1999a). If sea catch; however few fish were observed by creel lamprey control is continued it is estimated that clerks. Rainbow trout catch in other tributaries was members of 92,025 households currently recreating not evaluated. Estimated rainbow trout catch in the on Lake Champlain, and members of 58,542 house- Main Lake increased from 7 ± 11 (90% confidence holds not currently recreating on Lake Champlain, interval) fish in 1990 to 106 ± 82 (90% confidence will increase their annual participation by 1.5 mil- interval) in 1997. An increase in brown trout caught lion days and generate $59.3 million in additional per smolt stocked was seen in the Main Lake, Mal- annual water-based recreation expenditures. Sea Lamprey Control in Lake Champlain 671

TABLE 10. Sea lamprey wounding rates (sum of type AI–AIII wounds per 100 fish) by size group (mm TL) for adult landlocked salmon captured at the Willsboro Fishway, Main Lake open water creel surveys, and electroshocking surveys in the Lamoille River and Sandbar Bridge sites, pre- and post- sea lamprey control. Data were compared using a one-tailed t-test. Willsboro fishway Pre-control Post-control 1985-1992 1993-1998 % Size group NMean ±SDN Mean ±SDchangeP-value 432–532 43 51 ± 80 101 22 ± 46 –57 0.014 533–634 80 73 ± 89 157 44 ± 69 –40 0.007 635–736 32 156 ± 146 30 40 ± 62 –74 < 0.001

Main Lake Pre-control Post-control 1990 1997 % Size group NMean ±SDN Mean ±SDchange P-value 432–532 617 ±4189 8 ± 31 –53 0.255 533–633 40 25 ± 54 138 15 ± 43 –40 0.100 634–736 3167 ±5813 46 ± 78 –72 0.013 All Sizes 49 33 ± 63 240 14 ± 42 –42 0.024

Lamoille River (Malletts Bay) Pre-control Post-control 1986–1992 1993–1997 % Size group N Mean ±SD N Mean ±SD change P-value < 432 19 26 ± 45 6 58 ± 64 +123 0.094 432–532 200 32 ± 56 262 53 ± 74 +75 0.001 533–634 116 83 ± 93 185 71 ± 82 –14 0.122 635–736 31 77 ± 92 36 113 ± 131 +47 0.107

Sandbar Bridge (Inland Sea) Pre-control Post-control 1986–1992 1993–1997 % Size group N Mean ± SD N Mean ± SD change P-value < 432 17 0 17 12 ± 33 +120 0.007 432–532 191 42 ± 79 241 34 ± 52 –19 0.120 533–634 114 59 ± 75 156 65 ± 90 +10 0.280 635–736 47 104 ± 118 29 79 ± 94 –24 0.169

As part of a 1997 angler survey, current and non- fish other lakes said they would increase the num- current salmonid anglers were asked if they would ber of days they fish Lake Champlain to 16 days. increase number of days fished annually on Lake Owners of 98 fishing and fishing-related busi- Champlain if sea lamprey control is continued nesses serving Lake Champlain anglers were not (Gilbert 1999b). The estimated total increase was able to estimate the percentage of $5.5 million Lake 1.2 million days annually and average increase Champlain-based 1997 gross fishing/fishing-related ranged from 14.3 days (current salmonid anglers) to income attributable to the ESLCP; however, 48.5% 12.6 days (non-current, non-salmonid). This in- of these businesses expanded during the ESLCP crease is expected to generate an estimated $42.2 and business-owners attributed 29.2% of expansion million annually in fishing-related expenditures. In directly to the program (Gilbert 1999c). Another addition, an estimated 17,298 Lake Champlain an- 35.4% of business owners plan further expansion glers (20.5% of all Lake Champlain anglers) who and 21% of planned expansion was directly attrib- 672 Marsden et al. utable to anticipated continuation of sea lamprey relatively low pre-control wounding rates and nest control on Lake Champlain. counts, followed by increases in the late 1980s: nat- ural fluctuations in sea lamprey abundance; limited DISCUSSION ammocoete survival due to poor water quality in some tributaries, followed by improved water qual- The 8-year ESLCP in Lake Champlain success- ity; or increased salmonid populations due to stock- fully achieved the primary objectives of reduction ing and consequent increase in the lamprey food in the abundance of ammocoete and parasitic phase supply. A sufficiently long-term database on sea sea lamprey. A decrease in salmonid wounding and lamprey abundance in Lake Champlain does not scarring rates was observed, primarily in lake trout, exist to fully examine the first possibility. Similarly, and survival of lake trout increased significantly, stream water quality data are insufficient to validate but not substantially, between pre- and post-control the possibility of suppression of ammocoete sur- periods. There was a net benefit to the economy of vival by pollution. Certainly many rivers, such as the region as a consequence of increased recre- the LaPlatte River and Winooski River in Vermont ational use of Lake Champlain and its fisheries di- and the Pike River in Quebec, had episodic low dis- rectly related to sea lamprey control. Negative solved oxygen (unpubl. data) during the 1980s due effects on nontarget species did result from both to high inputs of agricultural and municipal efflu- TFM and Bayluscide treatments, however these ents, but the effect on sea lamprey cannot be esti- were largely temporary; similar or higher mortali- mated with any degree of certainty. Sewage ties in second treatments indicated minimal popula- treatment upgrades and higher minimum flows re- tion-level impacts for most nontarget species. sulting from hydropower relicensing have improved The conclusion that spawning phase sea lamprey water quality in the Winooski River. Young et al. populations have been reduced by two rounds of (1996) argue that lake trout stocking could be a fac- treatments in Lake Champlain is based on spawning tor in sea lamprey population increases, by increas- phase trapping in three streams, nest counts in 10 ing potential prey and therefore growth of sea streams, and indirect evidence from lake trout lamprey. However, the effect of salmonid stocking wounding. These data have a degree of uncertainty, on sea lamprey in Lake Champlain should have however. Pre-control trapping data on spawning been seen within a decade of the first substantial phase sea lamprey abundance are only available stockings, i.e., by 1984, but no increase in growth from a single tributary, Lewis Creek, monitored or number was detected. In addition, the apparent since 1982, and from 3 years of data each from increase in lake trout during the 1990s may either Stone Bridge Brook and Indian Brook. While sea have been due to increased stocking, or to reduction lamprey declined in each of these streams after each in the number of sea lamprey consequent to control. treatment, spawning phase sea lamprey numbers Population estimates for spawning phase sea lam- were as low or lower in Lewis Creek in 1982 and prey would facilitate evaluation of these effects. 1988 as they were after the first round of treatment. Lake trout wounding rates in Lake Champlain are These longer-term data suggest that lamprey popu- high compared to the Great Lakes; this may be due lations have undergone severe fluctuations prior to in part to the high potential for lamprey production recent control efforts. However, trap efficiency may in the basin. Average annual wounding rates for have varied due to changing flow conditions, which lake trout > 431 mm ranged from 33.3 to 80% pre- may affect accuracy of these data as an estimator of control, and 7.8 to 56.9% post-control. Wounds per relative abundance. Nest counts declined after treat- 100 lake trout > 431 mm ranged from 48 to 73 pre- ment in all assessed streams except the Poultney control and 24.4 to 52.2 post-control, compared River; the largest single reduction in nests occurred with a peak of 42 wounds per 100 lake trout > 431 in the Great Chazy River as a result of dam re-con- mm in (Sullivan et al. 2003). A relatively struction. Nest counts have not been validated as an large number of tributaries (approximately 105 per- index of spawning phase abundance. However, nest manent streams) drain into a relatively small lake; counts in the untreated Pike River can be used to the ratio of drainage area to lake area is over five evaluate changes in the spawning population. Pike times greater than any of the Great Lakes. In con- River nest abundance declined after control began, trast to the Great Lakes, where 8% of the tributaries suggesting that the overall sea lamprey population produce lamprey (Morman et al. 1980), approxi- in Lake Champlain was reduced. mately 20% of the tributaries in the Lake Cham- Three explanations have been suggested for the plain drainage produce lamprey. Unlike the Great Sea Lamprey Control in Lake Champlain 673

Lakes, Lake Champlain does not contain coho (O. paucity of catch data on the non-lake trout kisutch) and chinook salmon (O. tshawytscha) as al- salmonids. In addition, nest counts and lake trout ternate prey, so that lamprey attacks are concen- wounding rates were higher in 1988-1991 than in trated on lake trout. Wounding rates did decrease previous years. The effect of the control program significantly for most size-classes of lake trout after therefore appears to be large if compared to the initiation of sea lamprey control; however, this years immediately preceding the first treatment, but analysis is confounded by the probable increase in less dramatic if compared to data from 1982–1987. the salmonid prey base during the study period. Mortality among certain nontarget species Post-control wounding rates in Lake Champlain throughout the ESCLP, though high, was generally have not yet approached the low wounding rates consistent with predictions stated in the project EIS. targeted in Lake Erie (< 5 wounds per 100 lake As expected, Bayluscide treatments caused higher trout > 431 mm; Sullivan et al. 2003) or Lake On- mortality than TFM treatments; this difference sub- tario (< 2 AI wounds per 100 lake trout > 431 mm; stantially increased total nontarget mortality. Full Larson et al. 2003) evaluation of the impact of lampricide treatments Despite high wounding rates, lake trout survival on nontarget species is hindered by the lack of pop- in Lake Champlain is high compared to the Great ulation data for these species in the Lake Cham- Lakes, and increased through the period from 1979 plain basin. The contrast between higher Lake to 1997. Kitchell and Breck (1980) hypothesized Champlain and lower Great Lakes nontarget mor- that the duration, and therefore the possible lethal talities may be due to differences in monitoring and effect, of lamprey attacks decreases as prey abun- assessment methods for nontarget mortality, which dance increases. Therefore, as the population grew were necessarily more rigorous in Lake Champlain through stocking, the number of lake trout deaths than the standard methods used in the Great Lakes due to lamprey may have decreased. In addition, the due to permitting requirements. Assessments in majority of stocked lake trout were from the Seneca Lake Champlain may therefore have documented a Lake strain, which may be more resistant to lam- higher proportion of the actual nontarget mortali- prey predation than other strains stocked abun- ties. For example, assessment crews examined dantly in the Great Lakes (Swink and Hanson streams approximately 24 hours after initiation of 1986). Survival estimates for lake trout in Lake treatment rather than following the leading edge of Champlain are comparable with those from Seneca the treatment pulse as in the Great Lakes, and thus Lake (Engstom-Heg et al. 1990). Survival of older were more likely to pick up organisms that had a lake trout was greater than for younger lake trout, delayed response to the lampricide. Refinement of possibly reflecting increased resistance to lamprey TFM and Bayluscide application methods may re- attack by older, larger fish (Swink 1990). Curiously, duce nontarget mortality. Refinements under con- lake trout showed a trend before and during the sideration include more rigorous monitoring of ESLCP of decreasing length-at-age, although stream pH and alkalinity cycles, which substantially length-at-age still exceeds that of lake trout from affect toxicity; use of lower TFM concentrations at Seneca Lake (Engstrom-Heg and Kosowski 1991). the primary application point combined with use of Higher survival coupled with increased stocking intermediate application points to maintain the numbers may have led to an increase in intra-spe- chemical concentration; use of TFM:Bayluscide cific competition and consequent reduction in mixtures to increase efficacy of stream treatments, growth. Based on these comparisons of Lake and reducing the area of deltas treated with Baylus- Champlain and Great Lakes lake trout wounding cide by targeting locations where ammocoetes are and survival rates, the Cooperative established an likely to be concentrated, based on non-wadable acceptable long-term wounding rate objective of 25 waters larval assessment techniques (Slade et al. wounds per 100 lake trout in the 533–633 mm 2003). length class, with an ideal rate of 10 wounds per Following completion of the ESLCP on Lake 100 lake trout of this size for Lake Champlain Champlain, the Cooperative developed an exten- (Fisheries Technical Committee 2001). sive, integrated management approach to long-term Evaluation of wounding rates is confounded by sea lamprey control (Fisheries Technical Committee the fluctuating lake trout populations resulting from 2001). Future control may expand to include treat- changes in the stocking program, indirect evidence ment of previously untreated tributaries such as the of highly variable early survival (stocking to age 3), Winooski River and Pike River. Control methods difficulties with evaluation of catch data, and being considered for implementation in the long- 674 Marsden et al.

term sea lamprey control program include contin- suggests that sea lamprey may respond to treatment ued use of TFM and Bayluscide, and alternative by increasing growth, which decreases the size and methods such as use of different types of barriers age at metamorphosis (Zerrenner 2001). This re- (electrical and physical) to block upstream migra- search will be enhanced by progressive implemen- tion of spawning sea lamprey, and removal of tation of GLFC QAS protocols for habitat and spawning sea lamprey through trapping. Barrier ammocoete density assessment in Lake Champlain, dams are not feasible for many tributaries, unless enabling estimation of production in individual passage of migratory species is mitigated. The lack streams (Slade et al. 2003). of recolonization of Stone Bridge Brook following treatment in 1991 throughout 1997 (the last year in ACKNOWLEDGMENTS which monitoring occurred) suggests that complete elimination of sea lamprey ammocoetes from a We thank Pat Festa, Angelo Incerpi, David John- stream may result in long-term reduction of the son, Chet MacKenzie, Paul Neth, David Nettles, spawning population due to absence of attractants Gary Neuderfer, Dan Plosila, Larry Strait, and produced by ammocoetes (Sorenson and Vrieze David Tilton for their contributions to the sea lam- 2003). Research into the importance of pheromones prey control program. We also acknowledge the as attractors for spawning sea lamprey could be contributions of the late Gary Steinbach and Robert conducted at a number of small tributaries in the Engstrom-Heg. This work was funded by Federal basin. Use of other techniques such as sterile-male- Aid to Sport Fish Restoration Act Projects FA-40-R release (Twohey et al. 2003) will be considered if (New York) and F-23-R (Vermont), New York State future research demonstrates their efficacy. Conservation Fund appropriations, a special Con- The Cooperative completed a supplemental EIS gressional appropriation through the Great Lakes for long-term sea lamprey control to meet NEPA re- Fishery Commission, and the Lake Champlain Spe- quirements for use of federal funds and USFWS cial Designation Act of 1990. staff involvement in the program (Fisheries Techni- cal Committee 2001). Necessary state permits for REFERENCES tributary-specific control operations must also be Anderson, B.E., Guilmette, J.R., and Dudley, J.B. 1985. obtained, as well as Canadian regulatory approvals Preliminary feasibility study for sea lamprey barrier for control in the Pike River system. The cost-bene- dams on Lake Champlain tributary streams. Bureau fit data clearly support continued control of sea of Fisheries. NYSDEC, Ray Brook, NY. lamprey in Lake Champlain. However, the program Anderson, J.K. 1978. Lake Champlain fish population continues to face resistance from a vocal minority inventory, 1971–1977. Fisheries Technical Commit- of local individuals and organizations who object to tee, Lake Champlain Fish and Wildlife Management sea lamprey control largely based on their percep- Cooperative, Essex Junction, VT. tions of risk to nontarget organisms and general op- Bills, T.D., Boogaard, M.A., Johnson, D.A., Brege, D.C., position to use of pesticides in the environment. Scholefield, R.J., Westman, R.W., and Stephens, B.E. 2003. Development of a pH/alkalinity treatment Research to document the risks to potentially sensi- model for applications of the lampricide TFM to tive nontarget aquatic species from use of lampri- streams tributary to the Great Lakes. J. Great Lakes cides and other control methods, and commensurate Res. 29 (Suppl. 1):510–520. refinement of control methods to minimize the risks Daniels, R.A. 2001. Untested assumptions: the role of of nontarget impacts will be integral elements of the canals in the dispersal of sea lamprey, , and long-term program. other fishes in the eastern United States. Env. Biol. Due to the relatively small size of Lake Cham- Fishes 60:309–329. plain and recent initiation of sea lamprey control, Dean, M., and Zerrenner, A. 2000. Assessment of sea the lake presents some important contrasts with the lamprey habitat and the sea lamprey population of the Great Lakes and opportunities for research and Pike River and Morpion Stream, Quebec, Canada. management. For example, a lake-wide sea lamprey Final report, Lake Champlain Basin Program, Grand Isle, VT. tagging study to examine movement and relative Engstrom-Heg, R., and Kosowski, D.H. 1991. Evalua- contributions of individual streams to the parasitic tion of fishery impacts of lampricide treatments in the population is underway. Because a number of tribu- Seneca Lake system. Bureau of Fisheries, NYSDEC, taries have never been treated, the opportunity ex- Avon, NY. ists to examine responses of untreated sea lamprey ———, Gersmehl, J.E., LaBar, G.W., and Gilbert, A.H. populations to sea lamprey control. Recent research 1990. A comprehensive plan for the evaluation of an Sea Lamprey Control in Lake Champlain 675

eight year program of sea lamprey control in Lake King, E.L., and Edsall, T.A. 1979. Illustrated field guide Champlain. Fisheries Technical Committee, Lake for the classification of sea lamprey attack marks on Champlain Fish and Wildlife Management Coopera- Great Lakes lake trout. Great Lakes Fishery Commis- tive, Essex Junction, VT. sion Special Publication 79-1, Ann Arbor, MI. Evermann, B.W., and Kendall, W.C. 1902. An annotated Kitchell, J.F., and Breck, J.E. 1980. Bioenergetics model list of fishes known to occur in Lake Champlain and and foraging hypothesis for sea lamprey (Petromyzon its tributaries, pp. 217–225. U.S. Commission of Fish marinus). Can. J. Fish. Aquat. Sci. 37:2152–2168. and Fisheries. Commission Report for 1901. LaBar, G.W. 1993. Use of bioenergetics models to pre- Fabrizio, M.C., Swanson, B.L., Schram, S.T., and Hoff, dict the effect of increased lake trout predation on M.H. 1996. Comparison of three nonlinear models to rainbow smelt following sea lamprey control. Trans. describe long-term tag shedding by lake trout. Trans. Am. Fish. Soc. 122:942–950. Am. Fish. Soc. 125:261–273. Langdon, R., and Fiske, S. 1991. The effects of the lamp- Fichtel, C. 1992. Unionid mussels of the lower Poultney ricide TFM on non-target fish and macroinvertebrate River. Report on 1992 monitoring activities. VTDFW, populations in Lewis Creek, VT. VTDEC, Waterbury, Waterbury, VT. VT. Fisheries Technical Committee. 1977. A strategic plan Larson, G.L., Christie, G.C., Johnson, D.A., Koonce, for development of salmonid fisheries in Lake Cham- J.F., Mullet, K.M., and Sullivan, W.P. 2003. The his- plain. Lake Champlain Fish and Wildlife Manage- tory of sea lamprey control in and ment Cooperative. U.S. Fish and Wildlife Service, updated estimates of suppression targets. J. Great Essex Junction, VT. Lakes. Res. 29 (Suppl. 1):637–654. ——— . 1999. A comprehensive evaluation of an eight Lawrie, A.H. 1970. The sea lamprey in the Great Lakes. year program of sea lamprey control in Lake Cham- Trans. Am. Fish. Soc. 99:766–775. plain. Lake Champlain Fish and Wildlife Manage- Lyttle, M. 1996. Assessment of mussel populations on ment Cooperative. U.S. Fish and Wildlife Service, select delta areas of Lake Champlain following the Essex Junction, VT. application of lampricide (Bayer 73). USFWS, Essex ———. 2001. A long-term program of sea lamprey con- Junction, VT. trol in Lake Champlain. Final Supplemental Impact ——— , and Pitts, C. 1997. Investigations of native mussel Statement. FES 01-27. U.S. Fish and Wildlife Service, glochidia retention in the Poultney River during TFM Essex Junction, VT. treatment. USFWS, Essex Junction, VT. Gersmehl, J.E., and Baren, C.F. 1985. Lake Champlain MacKenzie, C. 1991. Impacts of TFM treatment on Sea Lamprey Assessment Report. USFWS, Essex caged eastern sand darters in Lewis Creek. VTDFW, Junction, VT. Pittsford, VT. Gilbert, A.H. 1999a. Benefit cost analysis of the eight- ——— . 1995. Impacts of TFM application on caged east- year experimental sea lamprey control program on ern sand darters in Lewis Creek, Ferrisburg, VT, Lake Champlain. VTDFW, Waterbury, VT. 1994. VTDFW, Pittsford, VT. ———. 1999b. Lake Champlain angler survey 1997. Morman, R.H., Cuddy, D.W., and Rugen, P.C. 1980. VTDFW, Waterbury, VT. Factors influencing the distribution of sea lamprey ——— . 1999c. A survey of fishing and fishing related (Petromyzon marinus) in the Great Lakes. Can. J. businesses serving Lake Champlain anglers. VTDFW, Fish. Aquat. Sci. 37:1811–1826. Waterbury, VT. Plosila, D.S., and Anderson, J.K. 1985. Lake Champlain Greeley, J.R. 1930. Fishes of the Lake Champlain Salmonid Assessment Report. Fisheries Technical Watershed. In Biological Survey of the Champlain Committee, Lake Champlain Fish and Wildlife Man- Watershed, pp. 44–87. New York Conservation agement Cooperative, Essex Junction, VT. Department. Supplement 19th annual report 1929. Rudstam, L.G., Magnuson, J.J., and Tonn, W.M. 1985. Gruendling, G.K., and Bogucki, D.J. 1993a. Assessment Size selectivity of passive fishing gear: a correction of the impacts of TFM on non-target macroinverte- for encounter probability applied to gill nets. Can. J. brates in Lake Champlain delta areas. Bureau of Fish. Aquat. Sci. 41:1252–1255. Fisheries. NYSDEC, Ray Brook, NY. Slade, J.W., Adams, J.V., Christie, G.C., Cuddy, D.W., ——— , and Bogucki, D.J. 1993b. Assessment of the Fodale, M.F, Heinrich, J.W., Quinlan, H.R., Weise, impacts of Bayer 73 (5% granular) on non-target J.G., Weisser, J.W., and Young, R.J. 2003. Tech- macroinvertebrates in Lake Champlain delta areas. niques and methods for estimating abundace of larval Bureau of Fisheries. NYSDEC, Ray Brook, NY. and metamorphosed sea lampreys in Great Lakes trib- Halnon, L.C. 1963. Historical survey of Lake Cham- utaries, 1995 to 2002. J. Great Lakes Res. 29 (Suppl. plain’s fishery. Vermont Fish and Game Department, 1):137–151. Essex Junction, VT. Smith, S.H. 1972. Factors of ecological succession in Holt , S.J. 1963. A method for determining gear selectiv- oligotrophic fish communities of the Laurentian Great ity and its application. ICNAF Spec. Publ. 5:106–115. Lakes. J. Fish. Res. Board Can. 29:717–730. 676 Marsden et al.

Sorenson, P.W., and Vrieze, L.A. 2003. The chemical VTDEC. 1994. The long term effects of the lampricide ecology and potential application of the sea lamprey TFM on nontarget fish and macroinvertebrate popu- migratory pheromone. J. Great Lakes Res. 29 (Suppl. lations in Lewis Creek, VT. Vermont Department of 1):66–84. Environmental Conservation, Waterbury, VT. Sullivan, W.P., Christie, G.C., Cornelius, F.C., Fodale, ———. 1996. The effects of a lampricide treatment of M.F., Johnson, D.A., Koonce, J.F., Larson, G.L., TFM on non-target fish and macroinvertebrates in McDonald, R.B., Mullett, K.M., Murray, C.K., and Trout Brook, Milton, Vermont—September, 1995. Ryan, P.A. 2003. The sea lamprey in Lake Erie: a VTDEC, Waterbury, VT. case history. J. Great Lakes Res. 29 (Suppl. Young, R.J., Christie, G.C., McDonald, R.B., Cuddy, 1):615–636. D.W., Morse, T.J., and Payne, N.R. 1996. Effects of Swink, W.D. 1990. Effect of lake trout size on survival habitat change in the St. Mary’s River and northern after a single sea lamprey attack. Trans. Am. Fish. on sea lamprey (Petromyzon marinus) Soc. 119:966–1002. populations. Can. J. Fish. Aquat. Sci. 53:99–104. ——— , and Hanson, L.H. 1986. Survival from sea lam- Zerrenner, A.E. 2001. Compensatory mechanisms in prey (Petromyzon marinus) predation by two strains Lake Champlain larval sea lamprey (Petromyzon mar- of lake trout (Salvelinus namaycush). Can. J. Fish. inus) populations: implications for sea lamprey con- Aquat. Sci. 43:2528–2531. trol. MS thesis, University of Vermont, Burlington Twohey, M.B., Heinrich, J.W., Seelye, J.G., Fredricks, VT 05405. K.T., Bergstedt, R.A., Kaye, C.A., Scholefield, R.J., McDonald, R.B., and Christie, G.C. 2003. The sterile- Submitted: 21 December 2000 male-release technique in Great Lakes sea lamprey man- Accepted: 26 December 2001 agement. J. Great Lakes Res. 29 (Suppl. 1):410–423. Editorial handling: John F. Heinrich