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Understanding fishing fleet dynamics is important when using fishery dependent data to infer the status of fish stocks. We analyzed data from mandatory catch reports from the commercial lake trout (Salvelinus namaycush) fishery in Michigan waters of Lake Superior during 1929-1961, a period when lake trout populations collapsed through the combined effects of overfishing and sea lamprey (Petromyzon marinus) predation. The number of full-time fishermen increased during 1933-1943 and then decreased during 1943-1957. Addition of new fishermen was related to past yield, market prices, World War II draft exemptions, and lost fishing opportunities in Lake Huron and Lake Michigan. Loss of existing fishermen was related...
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Newly hatched fry were acclimated to 7 or 12A?C and either fed daily (controls) or denied food for varying lengths of time and then fed daily until the end of the study (day 91 at 7A?C and day 43 at 12A?C). Growth was reduced by delays in the onset of feeding of 27 or more days at 7A?C and 7 or more days at 12A?C. Mortality of fry unfed for more than 34 days at 7A?C, or more than 21 days at 12A?C, was higher than among controls. Daily mortality increased with the length of the food deprivation period and did not cease immediately when food was made available, but reached zero by the end of the study. Mortality among unfed fry reached 50% in about 59 days at 7A?C and 32 days at 12A?C. Study results permitted calculation...
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In fisheries, imprecise measurements in catch data from surveys adds uncertainty to the results of fishery stock assessments. The USGS Great Lakes Science Center (GLSC) began to survey the fall fish community of Lake Michigan in 1962 with bottom trawls. The measurement error was evaluated at the level of individual tows for nine fish species collected in this survey by applying a measurement-error regression model to replicated trawl data. It was found that the estimates of measurement-error variance ranged from 0.37 (deepwater sculpin, Myoxocephalus thompsoni) to 1.23 (alewife, Alosa pseudoharengus) on a logarithmic scale corresponding to a coefficient of variation = 66% to 156%. The estimates appeared to increase...
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The lake trout (Salvelinus namaycush) stock at Gull Island Shoal in western Lake Superior was one of only a few stocks of lean lake trout in the Great Lakes that survived overfishing and predation by the sea lamprey (Petromyzon marinus). Since the mid 1960s, the abundance of wild recruits measured at age 0 and the number of age-7 to -11 wild fish recruited to the fishable stock have increased. We used the Varley-Gradwell method to test for density-dependent survival between these life stages. Survival from age-0 to ages 7–11 was not affected by increasing density, which suggests that further increases in recruitment and stock size are still possible. We suggest that testing for the existence of density-dependent...
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The importance of zooplankton in the diet of yellow perch (Perca flavescens), white perch (Morone americana), walleyes (Stizostedion vitreum vitreum), and white bass (M. chry-sops)was assessed in the central basin of Lake Erie in 1985–1988. Zooplankton were collected by vertical hauls in 1987–1988 and fish with a rock-hopper trawl. Although copepods (calanoid and cyciopoid) were the major zooplankton in the plankton samples, they were not well represented in the fish diet. From 1985 through 1988, Cladocera became an increasingly important food – particularly a recent invader from Europe, Bythotrephes cederstroemi. It was a major component in the diet of yellow perch from June to October in both 1987 and 1988. The...
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Alewives (Alosa pseudoharengus) were first reported in Lake Superior in 1954 and gradually increased in abundance in the late 1950s. In the 1960s and early 1970s, the fish were widespread in the lake but scarce. We determined the more recent abundance and distribution of alewives by cross-contour trawling in the spring in 1978–1988. Alewives were scarce lake-wide; the mean catch rate was only 23 fish per 100 h of trawling and represented a density of 0.003 kg per hectare in the area swept by the trawls. Fish of six age groups were caught in trawls in spring and gill nets in fall in 1983–1987. Total annual mortality was 64%, a high natural rate in the absence of fishing. Alewives in Lake Superior were small at the...
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Daily loads of suspended sediment and total phosphorus for the 10-year, 1-day design high flow and average of the 16-year period (1975 to 1990) were computed for 18 well-monitored tributaries to Lake Michigan and Lake Superior by use of constituent-transport models. The loads from these 18 reference tributaries were used to estimate the loads from all the United States tributaries (with drainage basins greater than 325 km2) to Lake Michigan and Lake Superior by selection of a reference tributary with the most similar physical characteristics and use of a unit-area yield. Statistical comparisons between computed yields and environmental factors were used to determine the physical characteristics that were most influential...
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Deepwater sculpin are important in oligotrophic lakes as one of the few fishes that use deep profundal habitats and link invertebrates in those habitats to piscivores. In Lake Ontario the species was once abundant, however drastic declines in the mid-1900s led some to suggest the species had been extirpated and ultimately led Canadian and U.S. agencies to elevate the species' conservation status. Following two decades of surveys with no captures, deepwater sculpin were first caught in low numbers in 1996 and by the early 2000s there were indications of population recovery. We updated the status of Lake Ontario deepwater sculpin through 2016 to inform resource management and conservation. Our data set was comprised...
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Adults of the cladoceran Daphnia lumholtzi, native to Australia, Africa, and parts of Asia, were first collected in August 1999 in Lake Erie. Individuals were collected near East Harbor State Park, Lakeside, Ohio from vertical plankton net tows. The average number of D. lumholtzi that were found (0.03/L) indicate that D. lumholtzi is beginning to establish itself in Lake Erie. The morphology of this Daphnia differs greatly from native species because of its elongated head and tail spine. This sighting is important because it acknowledges yet another exotic invader into the Great Lakes basin and it also shows that this, normally, warm water species continues to expand its range northward.
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The most common features are subcircular depressions, commonly compound, that are irregularly distributed across the lake floor. The depressions are most common in the southern basin of the lake where lacustrine sediments are more than a few meters thick, corresponding to water depths greater than about 90 m. We have divided the depressions into three types on the basis of their internal structure seen in seismic-reflection profiles. The depressions show varying degrees of muting, ranging from fresh to completely buried, suggesting a range in the time of their formation. The origin of the depressions is problematic, but their structure suggests collapse and(or) subsidence. -from Authors
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Fecundity (egg number) was determined from 26 stocked (617-800 mm, total length) lake trout (Salvelinus namaycush) collected in western Lake Ontario during September 1992. Previous to this study, fecundity was evaluated only once in Lake Ontario using native stocks in 1927. The following relationships between fecundity and total length (TL) and weight (W) were obtained. Fecundity = -12,492 + 25.87 TL(mm) and Fecundity = -1,010 + 1,307 W(kg). Relative fecundity (number of eggs per kg of body weight) was unrelated to body weight and averaged 1,592 eggs kg-1. Fecundity of contemporary lake trout based on length was significantly lower than that of historic native stocks, but was similar to contemporary stocked lake...
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The Lake St. Clair delta (??? 100??km2) provides an important refuge for native freshwater mussels (Unionidae) wherein 22 of the ??? 35 historical species co-occur with invasive dreissenids. A total of 1875 live unionids representing 22 species were found during snorkeling surveys of 32 shallow (??? 1??m) sites throughout the delta. Richness and density of unionids and zebra mussel infestation rates varied among sites from 3 to 13 unionid species, 0.02 to 0.12 unionids/m2, and < 1 to 35 zebra mussels/unionid, respectively. Zebra mussel infestation of unionids in the delta appears to be mitigated by dominant offshore currents, which limit densities of zebra mussel veligers in nearshore compared to offshore waters...
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Analysis of tissue composition in fish often requires dry samples. Time needed to dry fish decreases as temperature is increased, but additional volatile material may be lost. Effects of 10??C temperature increases on percentage dry mass (%DM) were tested against 60??C controls for groups of lake trout Salvelinus namaycush, rainbow smelt Osmerus mordax, slimy sculpin Cottus cognatus, and alewife Alosa pseudoharengus. Lake trout %DMs were lower at greater temperatures, but not significantly different from 60??C controls. Rainbow smelt and slimy sculpin %DMs were lower at greater temperatures and differences were significant when test temperatures reached 90??C. Significant differences were not found in tests using...
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We examined trends in species composition and abundance of the St. Marys River fish community. Abundance data were available approximately once every six years from 1975 through 2006, and size and age data were available from 1995 through 2006. We also compared survey data in 2006 with results of a concurrent creel survey that year, as well as data from prior surveys spanning a 69 year time frame. The St. Marys River fish community was best characterized as a coolwater fish community with apparent little variation in species composition, and only slight variation in overall fish abundance since 1975. However, we did find recent trends in abundance among target species sought by anglers: centrarchids increased, percids...
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We identified an objective set of 25 commonly available ecosystem metrics applicable across the world's large continental freshwater and brackish aquatic ecosystem. These metrics measure trophic structure, exploited species, habitat alteration, and catchment changes. We used long-term trends in these metrics as indicators of perturbations that represent an ecosystem not in homeostasis. We defined a healthy ecosystem as being in a homeostatic state; therefore, ecosystems with many changing trends were defined as more disturbed than ecosystems with fewer changing trends. Healthy ecosystems (lakes Baikal, Superior, and Tanganyika) were large, deep lakes in relatively unpopulated areas with no signs of eutrophication...
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Previously described models for predicting the percent of Lake Ontario wetlands that would be occupied by sedge/grass-dominated meadow marsh were used to test four proposed new plans for regulation of lake levels and to make comparisons with the current plan and unregulated conditions. The models for drowned river mouth, barrier beach, open embayment, and protected embayment wetlands assessed responses to lake levels that would be generated by each plan under net total supplies modified from those that occurred from1900 to 2000. In years when reduced supplies would allow meadow marsh regeneration, simulated unregulated lake levels produced the most meadow marsh in all wetland geomorphic types; current Plan 1958DD...
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The lake whitefish (Coregonus clupeaformis) is one of the native Lake Ontario fishes that declined severely over the past century. Recent evidence of larval lake whitefish production in a historic spawning area (Chaumont Bay) might signal a recovery of this species in New York waters. We surveyed coastal and open water areas to evaluate densities and estimate total abundance of larval lake whitefish in Chaumont Bay. Other historic spawning areas and embayments with appropriate spawning and nursery habitat were also surveyed, but only a few larvae were found outside of Chaumont Bay. Lake whitefish larvae were found in every embayment sampled within Chaumont Bay, with larval densities of nearly 600/1000 m2 in some...
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Coastal wetland seed banks exposed by low lake levels or through management actions fuel the reestablishment of emergent plant assemblages (i.e., wetland habitat) critical to Great Lakes aquatic biota. This project explored the effectiveness of using portable, water-filled cofferdams as a management tool to promote the natural growth of emergent vegetation from the seed bank in a Lake Erie coastal wetland. A series of dams stretching approximately 450??m was installed temporarily to isolate hydrologically a 10-ha corner of the Crane Creek wetland complex from Lake Erie. The test area was dewatered in 2004 to mimic a low-water year, and vegetation sampling characterized the wetland seed bank response at low, middle,...
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Progress toward lake trout restoration in Lake Michigan is described through 1993. Extinction of the native lake trout fishery by sea lamprey predation, augmented by exploitation and habitat destruction, resulted in an extensive stocking program of hatchery-reared lake trout that began in 1965. Sea lamprey abundance was effectively controlled using selective chemical toxicants. The initial stocking produced a measurable wild year class of lake trout by 1976 in Grand Traverse Bay, but failed to continue probably due to excessive exploitation. The overall lack of successful reproduction lakewide by the late 1970s led to the development and implementation in 1985 of a focused inter-agency lakewide restoration plan...
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Long-term trends in the abundance of unionids in the western basin of Lake Erie were examined from data collected at 17 stations in 1961, 1972, and 1982. The mean number of unionids at these stations declined over this time period, decreasing from 10 m−2 in 1961, to 6 m−2 in 1972, down to 4 m−2 in 1982. This decline in abundance was reflected in the decrease in the number of stations where mussels were found; unionids were found at 16 of the 17 stations in 1961, but at only 6 stations in 1982. Reasons for the decrease in the unionid population are not generally apparent, but are probably related to the decline in water quality and periods of low oxygen levels over the time period of the surveys.


map background search result map search result map Long-term trends in the St. Marys River open water fish community Metrics of ecosystem status for large aquatic systems: a global comparison Spatial and temporal variation in distribution of larval lake whitefish in eastern Lake Ontario: signs of recovery? Long-term decline in freshwater mussels (Bivalvia: Unionidae) of the western basin of Lake Erie Long-term decline in freshwater mussels (Bivalvia: Unionidae) of the western basin of Lake Erie Long-term trends in the St. Marys River open water fish community Spatial and temporal variation in distribution of larval lake whitefish in eastern Lake Ontario: signs of recovery? Metrics of ecosystem status for large aquatic systems: a global comparison