James W. Peck

Lake Trout (Salvelinus namaycush) Populations in Lake Superior and Their Restoration in 1959–1993

Naturally-reproducing populations of lake trout (Salvelinus namaycush) have been reestablished in most of Lake Superior, but have not been restored to 1929-1943 average abundance. Progress toward lake trout restoration in Lake Superior is described, management actions are reviewed, and the effectiveness of those actions is evaluated; especially stocking lake trout as a tool for building spawning stocks, and subsequently, populations of wild recruits. Widespread destruction of lake trout stocks in the 1950s due to an intense fishery and sea lamprey (Petromyzon marinus) predation resulted in lower overall phenotypic diversity than was previously present. Stocking of yearling lake trout, begun in the 1950s, produced high densities of spawners that reproduced wherever inshore spawning habitat was widespread. Sea lampreys were greatly reduced, beginning in 1961, using selective chemical toxicants and barrier dams, but continue to exert substantial mortality. Fishery regulation was least effective in Wisconsin, where excessive gillnet effort caused high by-catch of lake trout until 1991, and in eastern Michigan, where lake trout restoration was deferred in favor of a tribal fishery for lake whitefish (Coregonus clupeaformis) in 1985. Restoration of stocks was quicker in offshore areas where remnant wild lake trout survived and fishing intensity was low, and was slower in inshore areas where stocked lake trout reproduced successfully and fishing intensity was high. Inshore stocks of wild lake trout are currently about 61 % of historic abundance in Michigan and 53% in Wisconsin. Direct comparison of modern and historic abundances of inshore lake trout stocks in Minnesota and Ontario is impossible due to lack of historic stock assessment data. Stocks in Minnesota are less abundant at present than in Michigan or Wisconsin, and stocks in Ontario are similar to those in Michigan. Further progress in stock recovery can only be achieved if sea lampreys are depressed and if fisheries are constrained further than at present.

Comparison of Lake Trout-Egg Survival at Inshore and Offshore and Shallow-Water and Deepwater Sites in Lake Superior

We incubated lake trout (Salvelinus namaycush) eggs over winter at shallow (10 m) and deep locations (20 m) on Gull Island Shoal, Lake Superior; at a shallow-water (10 m) site off the mainland (Bark Point); and in flowing Great Lakes water at two laboratories. Survival to hatch was significantly higher in the laboratories and averaged 80.9%. In Lake Superior, egg survival among incubators at all sites was significantly higher (P < 0.0001) for incubators that remained buried in spawning substrates (15.1–21.0%) than for incubators that were partially or completely exposed to water currents (1.0–12.6%). Egg survival for incubators that remained buried at the shallow-water sites was significantly higher at Bark Point (44.6%) than at Gull Island Shoal (21.0%). Egg survival among incubators that remained buried at the deep (14.4%) and shallow-water sites (21.0%) on Gull Island Shoal was not significantly different. Because incubators that were completely buried or partially exposed only appeared to differ in their degree of exposure, we concluded that survival of eggs in the lake was reduced by mechanical stress associated with water turbulence. Lower egg survival at Gull Island Shoal, a known lake trout-spawning site, was not expected and appeared to have been caused by a strong gale that occurred when these eggs were in late epiboly, a sensitive embryological stage. We present a hypothesis suggesting that lake trout recruitment in the Great Lakes is limited by availability of spawning habitat.

Contribution of Hatchery-Reared Fish to Chinook Salmon Populations and Sport Fisheries in Lake Superior

Abstract Chinook salmon Oncorhynchus tshawytscha stocked in Lake Superior since 1967 to diversify the sport fishery were suspected of reproducing. An abundance of naturalized chinook salmon would reduce the need for hatchery fish but also would decrease our ability to manage chinook populations and their effect on the Lake Superior fish community. Our study objective was to determine the relative contribution of hatchery and wild fish to chinook salmon populations in Lake Superior. All chinook salmon stocked in Lake Superior in 1988, 1989, and 1990 were marked with an agency-specific fin clip. Contribution of these marked year-classes were determined from their representation in sampled sport fisheries and spawning runs. Hatchery fish made up 9, 25, 32, and 57% of chinook salmon sampled in Ontario, Michigan, Wisconsin, and Minnesota waters of Lake Superior during 1990–1994. Hatchery chinook salmon stocked by each state or provincial agency were caught in each of the other Lake Superior jurisdictions, and ...

Food of Young-of-the-Year Lake Trout (Salvelinus Namaycush) in Presque Isle Harbor, Lake Superior

Abstract The food habits of young lake trout ( Salvelinus namaycush ) were studied by examining the digestive tracts of 293 young-of-the-year collected in Presque Isle Harbor, Lake Superior. Lake trout in the 25 to 27-mm length range started to eat food organisms before all of their yolk material was absorbed. Organisms consumed by the 25 to 27-mm young-of-the-year included Chironomidae, Copepoda (Harpacticoida, Calanoida, Cyclopoida), and Cladocerea ( Daphnia spp., Bosmina sp., Chydorus sp.). Chironomid pupae and chironomid larvae accounted for 74% and 5%, respectively, of the total volume of food eaten by the young lake trout in Presque Isle Harbor. Although copepods, cladocerans, and mysids were present in many stomachs, their contribution to the total volume of food was only 15%. Some lake trout in the 32 to 54-mm length range had consumed fry of sculpin ( Cottus spp.) or rainbow smelt ( Osmerus mordax ), but the overall contribution of fish fry to the total volume of food was only 4% (frequency of occurrence, 10%). The lake trout in Presque Isle Harbor fed heavily on planktonic organisms, sparingly on benthic organisms, and were opportunistic feeders that appeared to prey on whatever forage organisms were available in the shallow nearshore waters.

Extended Residence of Young-of-the-Year Lake Trout in Shallow Water

Abstract Young-of-the-year lake trout Salvelinus namaycush remained at depths of 2–8 m in Presque Isle Harbor, Lake Superior from May through July. This extended residence in shallow depths contrasts with an immediate migration to deeper water reported by others. The young lake trout attained average total lengths of 45 mm before they left shallow water. Movement to deeper water was judged to be associated with water temperatures greater than 15 C and a preference for deep water 12 weeks after hatching.

Survival of Lake Trout Eggs on Reputed Spawning Grounds in Lakes Huron and Superior: in situ Incubation, 1987–1988

Lake trout reproduce widely in Lake Superior but little in Lake Huron. We examined whether survival of lake trout eggs and fry in either lake was reduced by physical disturbances and swim-up mortality. Eggs were collected from feral lake trout in Lake Superior and placed in 108 plastic incubators. A total of 48 incubators was set at Partridge Island Reef in southern Lake Superior, 48 were set at Port Austin Reef in southern Lake Huron, and 12 were held as controls inflowing well water at a laboratory. Survival-to-hatching of these eggs at Partridge Island Reef (18%) was significantly different from that at Port Austin Reef (43%) and significantly different in the laboratory (88%) from that at either reef (P < 0.05). During egg-fry incubation from 28 October 1987 to 5 May 1988, 11–18 cm of sediment accumulated in sediment traps placed on the reefs but < 1 cm of sediment was present on each reef in May 1988. Analysis showed that 44% of the eggs at Port Austin Reef and 28% of those at Partridge Island Reef were buried and killed by sediments. During the first week after deployment, mean wave energy was 90% higher at Partridge Island Reef and significantly different from that at Port Austin Reef. Wave energy may be a habitat condition that makes Partridge Island Reef less suitable than Port Austin Reef for incubation of lake trout eggs. Fry from eggs incubated at all three sites experienced no swim-up mortality. We conclude that in 1987–88 habitat conditions required for survival of lake trout eggs were more suitable at Port Austin Reef than at Partridge Island Reef.

Survey of angling in Lake Superior waters at Isle Royale National Park, 1998.

Abstract An on-site direct-contact creel survey was conducted in the Lake Superior waters of Isle Royale National Park during June–August 1998 to estimate fishing effort, sport catch, sport harvest, and residency of noncharter boaters. The sport harvest of lake trout Salvelinus namaycush and coaster brook trout S. fontinalis was of particular concern. Estimates were based on boat counts from air flights and from the ferry vessel Voyageur II, as well as from interviews of boating parties at Isle Royale, Michigan, ports; at Grand Portage, Minnesota; and onboard the ferry vessel Ranger III. Total boating effort at Isle Royale National Park during June–August was 29,273 h, of which 696 h (2%) involved charter fishing boats, 19,340 h (66%) noncharter fishing boats, and the remaining 9,237 h (32%) nonfishing boats. Most boaters were from Minnesota and Michigan, which together accounted for 95% of the noncharter anglers and 70% of the nonfishing boaters. Total angler hours for the period were 62,232. Lake trout ...

Migration, Food Habits, and Predation on Yearling Coho Salmon in a Lake Michigan Tributary and Bay

Abstract Migration of newly planted yearling coho salmon (Oncorhynchus kisutch) out of a Lake Michigan tributary and through the connecting bay was monitored with trap nets and pound nets in April-June 1968 and 1969. Concurrently, food habits of coho and their potential piscine predators were examined. Yearling coho migrated out of the Whitefish River within 2 wk and through northern Little Bay de Noc within 4 wk. They fed primarily on insects and crustaceans in both river and bay. Coho were eaten by only 2 of 221 predatory fishes examined. Thus, yearling coho did not prey upon or compete significantly with native game fishes for food, nor were they utilized as food extensively by resident fishes.