Geology topics

Gregory W. Kennedy

Publications and source records attributed to Gregory W. Kennedy.

25 records · Page 2Linked to original sources

USGS1995

Availability of lake trout reproductive habitat in the Great Lakes

A decades-long program to reestablish self-sustaining stocks of lake trout ( Salvelinus namaycush ) in the four lower Great Lakes produced excellent fisheries supported by stocked fish. These fish spawned widely and small numbers of their offspring were collected intermittently from Lakes Michigan, Huron, and Ontario, but no self-sustaining stocks were established. Irt this paper we address habitat sufficiency as a factor in the failure of stocked lake trout to established self-sustaining populations in the four lower Great Lakes. We present the previously unpublished results of lake trout spawning habitat surveys conducted at seven sites in the Great Lakes since 1987 and we compare them with the published results of similar surveys conducted at 24 other sites in the four lower lakes since 1981. Our evaluation indicates all but two of these sites can support the production of viable fry from spawnings by the shallow-water strains of lake trout that are stocked in the Great Lakes. However, some of the best spawning, egg, and fry habitat in the lower Great Lakes seems to be at deeper offshore sites that may be unattractive to these shallow-water strains. Thus, we suggest also stocking the lower four lakes with strains from Lake Superior that might more fully exploit the best spawning habitat at these deeper, offshore sites.

Journal of Great Lakes Research↗

USGS1995

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.

Journal of Great Lakes Research↗

USGS1995

An evaluation of lake trout reproductive habitat on Clay Banks Reef, northwestern Lake Michigan

The extinction of the native populations of lake trout ( Salvelinus namaycush ) in Lake Michigan in about 1956 has been followed by a decades-long attempt to reestablish self-sustaining populations of this valuable species in habitats it formerly occupied throughout the lake. One of the most recent management strategies designed to facilitate recovery was to make a primary management objective the establishment of sanctuaries where stocked lake trout could be protected and self-sustaining populations reestablished. In the present study we employed habitat survey and mapping techniques, field and laboratory bioassays, egg traps, sediment traps, and gill nets to examine the potential for successful natural reproduction by stocked lake trout on Clay Banks Reef in the Door-Kewaunee sanctuary in Wisconsin waters of Lake Michigan. Our study revealed (1) there was suitable habitat on the reef to support the production of viable fry, (2) spawner abundance on the reef was the highest recorded in the great lakes, and (3) eggs taken from spawners on the reef and held on the reef in plexiglas incubators hatched and produced fry that survived through swim-up. We conclude that Clay Banks Reef has the potential to support successful natural reproduction by stocked lake trout.

Journal of Great Lakes Research↗

USGS1993

Distribution, abundance, and resting microhabitat of burbot on Julian's Reef, southwestern Lake Michigan

We used a remotely operated submersible vehicle equipped with a color video camera to videotape the lake bed and document the distribution and abundance of burbot Lota lota on a 156‐hectare portion of Julianˈs Reef in southwestern Lake Michigan. The substrates and bathymetry of the study area had been mapped recently by side‐scan sonar. Burbot density determined from videotapes covering 6,900 m 2 of lake bed at depths of 23–41 m averaged 139 individuals/ hectare (range, 0–571/hectare). This density was substantially higher than the highest burbot density (59–95/hectare) reported in the literature. Burbot were present on the lake bed at depths of 23–36 m, but were most abundant near the crest of the reef at 23–28 m, where the water temperature was 8–13°C, their preferred summer temperature range. Substrates in that temperature range on the reef were bedrock, bedrock ridges, and bedrock and rubble. Burbot were most abundant on the bedrock and rubble. Small fish and macroinvertebrates typically eaten by burbot elsewhere in western Lake Michigan were distributed on the reef according to their summer preferred temperatures and were not seen in abundance where burbot density was highest. We saw no lake trout Salvelinus namaycush on Julianˈs Reef, although large numbers of juvenile lake trout have been stocked there annually and temperatures on the reef were in the preferred summer temperature range for lake trout.

Michigan, Wisconsin↗

USGS1992

Lake trout spawning habitat in the Six Fathom Bank-Yankee Reef lake trout sanctuary, Lake Huron

Attempts to reestablish self-sustaining stocks of lake trout ( Salvelinus namaycush ) in the lower four Great Lakes, where the species was extinguished in the 1950s and 1960s, have been largely unsuccessful. To avoid many of the problems believed to be contributing to this failure, the fishery management community recently established several sanctuaries in the offshore waters of the Great Lakes where the development and protection of self-sustaining stocks of lake trout would be a primary management objective. One of these, the Six Fathom Bank-Yankee Reef sanctuary, was created in the south-central portion of Lake Huron. This sanctuary covers 168,000 ha and includes the shallower portions of the Six Fathom and Ipperwash scarps, which are major bathymetric features in the southern half of the lake. Historical accounts describe Six Fathom Bank as the most important lake trout spawning ground in the lake. Here we present the results of lake bed surveys conducted in the sanctuary with side-scan sonar, underwater videocamera systems, and a small research submarine. Our observations of the lake bed are consistent with what is known of the bedrock stratigraphy, glacial history, and karst geomorphology of the Lake Huron basin. Most of the loose rock we found seemed to be derived from local carbonate bedrock formations, although non-carbonate rock probably from Precambrian sources to the north was also present in some areas. Much of the bedrock and loose rock displayed karst solution features described for the Bruce Peninsula on the Ontario shoreline. Our surveys revealed substantial areas of lake bed at water depths of 20–36 m that resembled suitable spawning and fry production habitat for the shallow-water strains of lake trout that are the focus of the rehabilitation effort. Low mid-lake nutrient levels documented recently by others and the extremely high abundance of Mysis relicta (an important item in the diet of young lake trout) that we documented on Yankee Reef also contributed to our evaluation of the sanctuary as a site with high potential to support a self-sustaining population of lake trout.

Journal of Great Lakes Research↗

USGS1992

Surficial substrates and bathymetry of five historical lake trout spawning reefs in near-shore waters of the Great Lakes

The reestablishment of self-sustaining stocks of lake trout (Salvelinus namaycush) in the lower four Great Lakes has been substantially impeded because planted fish do not produce enough progeny that survive and reproduce. The causes for this failure are unknown, but many historical spawning sites of lake trout have been degraded by human activities and can no longer produce viable swim-up fry. In this study, we used side-scan sonar and an underwater video camera to survey, map, and evaluate the sustainability of one reef in each of the five Great Lakes for lake trout spawning and fry production. At four of the reef sites, we found good-to-excellent substrate for spawning and fry production by the shallow-water strains of lake trout that are now being planted. These substrates were in water 6-22 m deep and were composed largely of rounded or angular rubble and cobble. Interstitial spaces in these substrates were 20 cm or deeper and would protect naturally spawned eggs and fry from predators, ice scour, and buffeting by waves and currents. Subsequent studies of egg survival by other researchers confirmed our evaluation that the best substrates at two of these sites still have the potential to produce viable swim-up fry.

Technical Report↗

USGS1988

Fishery research in the Great Lakes using a low-cost remotely operated vehicle

We used a MiniROVER MK II remotely operated vehicle (ROV) to collect ground-truth information on fish and their habitat in the Great Lakes that have traditionally been collected by divers, or with static cameras, or submersibles. The ROV, powered by 4 thrusters and controlled by the pilot at the surface, was portable and efficient to operate throughout the Great Lakes in 1987, and collected a total of 30 h of video data recorded for later analysis. We collected 50% more substrate information per unit of effort with the ROV than with static cameras. Fish behavior ranged from no avoidance reaction in ambient light, to erratic responses in the vehicle lights. The ROV's field of view depended on the time of day, light levels, and density of zooplankton. Quantification of the data collected with the ROV (either physical samples or video image data) will serve to enhance the use of the ROV as a research tool to conduct fishery research on the Great Lakes.

Conference Paper↗