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At least 397 records · Page 22Linked to original sources
USGS1973

Lake Michigan: Man's effects on native fish stocks and other biota

Man's activities have caused great changes in Lake Michigan in the past 120 years. Although changes in water chemistry and lower biota have been generally modest (except locally), those in native fish stocks have been vast. Exploitation, exotic fish species, and eutrophication and other forms of pollution all have played a role in bringing about the changes (mostly declines in abundance) in fish populations. Exploitation resulted in a noticeable reduction in abundance of certain native species (especially whitefish) soon after the establishment of the commercial fishery in the 1840's. By the 1930's the sturgeon and the two largest deepwater ciscoes (Coregonus nigripinnis and C. johannae) became severely depleted. Other species- whitefish (Coregonus clupeaformis), lake trout (Salvelinus namaycush), and lake herring (C. artedii)- remained important commercially, but at a lower level of production than originally; greatly increased fishing effort and efficiency were required to maintain even these decreased catches. The catch of intermediate-size ciscoes held relatively stable, but again only through sharply increased fishing effort and efficiency. The earliest serious effects of exotic fish species on native fish stocks may have been during the 1930's, when smelt (Osmerus mordax), first became abundant. Powerful influences by exotics were not obvious, however, until the 1940's, when the sea lamprey's (Petromyzon marinus) predation on several species, particularly the lake trout, became critical. In the 1950's the sea lamprey was joined by the alewife (Alosa pseudoharengus), another exotic strongly deleterious to several native fish. The alewife apparently inhibited reproduction of deepwater ciscoes, yellow perch (Perca flavescens), deepwater sculpins (Myoxocephalus quadricornis), emerald shiners (Notropis atherinoides), and perhaps others (through competing with young, or feeding on them). At the same time, however, the alewife as a prolific forage fish has made possible the highly successful introduction of several species of salmonines. The effects of accelerated eutrophication and other pollution, although not always as easy to identify as the influences of other factors, were nevertheless clearly important as early as the mid-1800's. The first conspicuous contamination of Lake Michigan was by sawmill wastes, which covered spawning grounds in streams and around stream mouths. This type of pollution was particularly destructive to whitefish. Other forms of stream degradation (e.g., dams, deforestation of watersheds) although not strictly "pollution," must also have been detrimental to stream spawners. Heavy pollution in southern Green Bay (a large area of the bottom of which is now covered with anoxic gray sludge) probably has resulted in reduction in abundance of several species, e.g., lake herring and walleye (Stizostedion v. vitreum). Exploitation was largely responsible for the changes in Lake Michigan fish stocks before the invasion of the smelt, and probably before the invasion of the sea lamprey. The lamprey and alewife, however, have exerted a greater impact than the fishery on native fish populations in recent decades. Accelerated eutrophication and other pollution, although important, have not equalled the other factors in causing changes in native fish populations.

Technical Report↗
USGS1990

Genetic differentiation of walleye stocks in Lake St. Clair and western Lake Erie

Allozyme data from six spawning sites of walleyes (Stizostedion vitreum vitreum) in western Lake Erie and two in Lake St. Clair demonstrated significant differences between allelic frequencies in fish from the two lakes. In contrast, differences were only slight between walleyes from different spawning sites within each lake. Of 21 presumptive genetic loci assayed electrophoretically, 4 were polymorphic enough to differentiate the populations. Allelic frequencies differentiating the stocks were stable between year classes, sexes, and sample years, showing that fry hatched in a particular area were returning there to spawn. These findings support other evidence for homing in Great Lakes walleyes.

Fish and Wildlife Technical Report↗
USGS1993

Food of salmonine predators in Lake Superior, 1981-87

Diets of ten species of Lake Superior salmonines are described. Rainbow smelt (Osmerus mordax) were the primary prey during all seasons and years for inshore lake trout (Salvelinus namaycush), Pacific salmon (Oncorhynchus spp.), Atlantic salmon (Salmo salar), brown trout (S. trutta), brook trout (Salvelinus fontinalis), and splake (lake trout x brook trout hybrid). Coregonines were the second most-important prey for chinook salmon (O. tshawytscha), siscowet trout (S. namaycush siscowet), and splake. Invertebrates were important to rainbow trout (O. mykiss), coho salmon (O. kisutch), and pink salmon (O. gorbuscha), especially during the summer. Diets of lake trout from inshore and offshore locations differed markedly. Rainbow smelt were the primary food of inshore lake trout, and coregonines were the main food of offshore lake trout. Chinook salmon and inshore lake trout had the most similar diets because they ate similar proportions of rainbow smelt and coregonines. Salmonines generally ate more rainbow smelt and less coregonines in proportion to the abundance of these prey in the lake. If rainbow smelt populations collapse, the ability of salmonines to convert to a diet based on lake herring (Coregonus artedi) could be important to the stability of predator populations.

Technical Report↗
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↗
USGS1999

Effects of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) on pH, net oxygen production, and respiration by algae

The lampricide 3-trifluoromethyl-4-nitrophenol (TFM) has been used in the United States and Canada for more than 35 years to control larval sea lampreys (Petromyzon marinus) in tributaries of the Great Lakes. Occasionally, during stream treatments with TFM, nontarget-fish mortality reaches unacceptable levels. These losses could be due to the presence of sensitive fish species, excess TFM, or a combination of factors that influence the toxicity of TFM, such as delays in daily stream reaeration by algae resulting in extended periods of low pH and low dissolved oxygen (DO). We determined the effects of a broad range of TFM concentrations on net DO production and respiration by two species of algae, in two culture media (high alkalinity and low alkalinity). The pH and DO in cultures of Chlorella pyrenoidosa and Selenastrum capricornutum were recorded at time zero and again after a 9-h exposure to TFM under either lighted or dark conditions. Algal cultures exposed to TFM concentrations typical of those used to control sea lampreys in streams showed only small changes in pH (<0.1) and small reductions in DO (about 8% in lighted conditions and 11% in dark conditions). Changes in pH and DO of this magnitude probably do not change the efficacy of TFM or cause nontarget fish mortality if algae are the predominant photosynthetic organisms in the stream.

Technical Report↗
USGS1997

Validation of behave fire behavior predictions in oak savannas

Prescribed fire is a valuable tool in the restoration and management of oak savannas. BEHAVE, a fire behavior prediction system developed by the United States Forest Service, can be a useful tool when managing oak savannas with prescribed fire. BEHAVE predictions of fire rate-of-spread and flame length were validated using four standardized fuel models: Fuel Model 1 (short grass), Fuel Model 2 (timber and grass), Fuel Model 3 (tall grass), and Fuel Model 9 (hardwood litter). Also, a customized oak savanna fuel model (COSFM) was created and validated. Results indicate that standardized fuel model 2 and the COSFM reliably estimate mean rate-of-spread (MROS). The COSFM did not appreciably reduce MROS variation when compared to fuel model 2. Fuel models 1, 3, and 9 did not reliably predict MROS. Neither the standardized fuel models nor the COSFM adequately predicted flame lengths. We concluded that standardized fuel model 2 should be used with BEHAVE when predicting fire rates-of-spread in established oak savannas.

General Technical Report↗
USGS1995

Point counts of birds: what are we estimating?

Point counts of birds are made for many reasons, including estimating local densities, determining population trends, assessing habitat preferences, and exploiting the activities of recreational birdwatchers. Problems arise unless there is a clear understanding of what point counts mean in terms of actual populations of birds. Criteria for conducting point counts depend strongly on the purposes to which they will be put. This paper provides a simple mathematical conceptualization of point counts and illustrates graphically some of the influences on them.

General Technical Report↗
USGS1987

Bird behavior and mortality in relation to power lines in prairie habitats

Research was conducted to determine the magnitude of avian mortality caused by power transmission lines in prairie habitats during the two spring and two fall migration periods between July 1980 and May 1982. Searches for dead birds were made at least twice weekly during each migration period. Study sites were selected to include 'worst-case' situations involving potentially large concentrations of birds.In total, 633 dead birds were found beneath 9.6 km of power lines. About 81% of the birds were found during fall migration. Removal of birds by scavengers was of minor, although local, importance, and observer error in finding birds was greatest in areas of dense vegetation. Total kill was estimated at 1,332 birds.Data were gathered on more than 7,000 bird flights observed in the vicinity of the power lines. Sixty-eight percent of the birds did not respond to the presence of the power lines. Flaring and climbing over the conductor or overhead ground wire occurred in about 25% of the flights. One hundred nine birds in 82 flocks were observed to collide with a power line. Of these birds, 87% flared to climb over the power line before colliding. The overhead ground wire was responsible for most deaths, as 102 of 109 birds collided with it.Whereas none of the mortality observed was considered to be biologically significant at the particular sites examined, the cumulative effect of mortality sustained from collisions with power lines may be important, particularly to populations of rare or endangered birds.

Technical Report↗
USGS1986

Effects of vegetation manipulation on breeding waterfowl in prairie wetlands--a literature review

Literature on the effects of fire and grazing on the wetlands used by breeding prairie waterfowl is reviewed. Both dabbling and diving ducks and their broods prefer wetlands with openings in the marsh canopy. Decreased use is commonly associated with decreased habitat heterogeneity caused by tall, robust hydrophytes such as Typha spp. and other species adapted to form monotypes in the absence of disturbance. Nearly all previous studies indicate that reductions in height and density of tall, emergent hydrophytes by fire and grazing (unless very intensive) generally benefit breeding waterfowl. Such benefits are an increase in pair density, probably related to increased interspersion of cover and open water which decreases visibility among conspecific pairs, and improvements in their invertebrate food resources that result from increased habitat heterogeneity. Research needs are great because of the drastic changes that have accrued to prairie wetlands through fire suppression, cultivation, and other factors. The physical and biological environments preferred by species of breeding waterfowl during their seasonal and daily activities should be ascertained from future studies in wetland complexes that exist in the highest state of natural preservation. Long-term burning and grazing experiments should follow on specific vegetatively-degraded wetlands judged to be potentially important breeding areas. Seasonality, frequency, and intensity of treatments should be varied and combined and, in addition to measuring the response of the biotic community, the changes in the physical and chemical environment of the wetlands should be monitored to increase our knowledge of causative factors and possible predictive values.

Fish and Wildlife Technical Report↗
USGS1988

Applications of a simulation model to decisions in mallard management

A system comprising simulation models and data bases for habitat availability and nest success rates was used to predict results from a mallard (Anas platyrhynchos) management plan and to compare six management methods with a control. Individual treatments in the applications included land purchase for waterfowl production, wetland easement purchase, lease of uplands for waterfowl management, cropland retirement, use of no-till winter wheat, delayed cutting of alfalfa, installation of nest baskets, nesting island construction, and use of predator-resistant fencing.The simulations predicted that implementation of the management plan would increase recruits by 24%. Nest baskets were the most effective treatment, accounting for 20.4% of the recruits. No-till winter wheat was the second most effective, accounting for 5.9% of the recruits. Wetland loss due to drainage would cause an 11% loss of breeding population in 10 years.The models were modified to account for migrational homing. The modification indicated that migrational homing would enhance the effects of management. Nest success rates were critical contributions to individual management methods. The most effective treatments, such as nest baskets, had high success rates and affected a large portion of the breeding population.Economic analyses indicated that nest baskets would be the most economical of the three techniques tested. The applications indicated that the system is a useful tool to aid management decisions, but data are scarce for several important variables. Basic research will be required to adequately model the effect of migrational homing and density dependence on production. The comprehensive nature of predictions desired by managers will also require that production models like the one described here be extended to encompass the entire annual cycle of waterfowl.

Fish and Wildlife Technical Report↗