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William Edwards

Publications and source records attributed to William Edwards.

6 recordsLinked to original sources
USGS2015

Females exceed males in mercury concentrations of burbot Lota lota

Examination of differences in contaminant concentrations between sexes of fish, across several fish species, may reveal clues for important behavioral and physiological differences between the sexes. We determined whole-fish total mercury (Hg) concentrations of 25 male and 25 female adult burbot Lota lota captured in Lake Erie during summer 2011, and of 14 male and 18 female adult burbot captured in Great Slave Lake (Northwest Territories, Canada) during winter 2013. On average, females were 22 % greater in Hg concentration than males. This difference was probably not due to a greater feeding rate by females, because results from previous studies based on polychlorinated biphenyl (PCB) determinations of these same burbot indicated that males fed at a substantially greater rate than females. Based on our determinations of Hg concentrations in the gonads and somatic tissue of five ripe females and five ripe males, this difference was not attributable to changes in Hg concentration immediately after spawning due to release of gametes. Further, bioenergetics modeling results from previous studies indicated that growth dilution would not explain any portion of this observed difference in Hg concentrations between the sexes. We, therefore, conclude that this difference was most likely due to a substantially faster rate of Hg elimination by males compared with females. Male burbot exhibit among the greatest gonadosomatic indices (GSIs) of all male fishes, with their testes accounting for between 10 and 15 % of their body weight when the fish are in ripe condition. Androgens have been linked to enhanced Hg elimination rates in other vertebrates. If androgen production is positively related to GSI, then male burbot would be expected to have among the greatest androgen levels of all fishes. Thus, we hypothesize that male burbot eliminate Hg from their bodies faster than most other male fishes, and this explains the greater Hg concentration in females compared with males.

Archives of Environmental Contamination and Toxico↗
USGS2015

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2014

In 2014, the USGS LEBS successfully completed large vessel surveys in all three of Lake Erie’s basins. Lake Erie Biological Station’s primary vessel surveys included the Western Basin Forage Fish Assessment and East Harbor Forage Fish Assessment as well as contributing to the cooperative multi-agency Central Basin Hydroacoustics Assessment, the Eastern Basin Coldwater Community Assessment, and LTLA (see FTG, CWTG, and FTG reports, respectively). Results from the surveys contribute to Lake Erie Committee Task Group data needs and analyses of trends in Lake Erie’s fish communities. The cruise survey schedule in 2014 was greatly increased by LEBS’s participation in the Lake Erie CSMI, which consisted of up-to two weeks of additional sampling per month from April to October. CSMI is a bi-national effort that occurs at Lake Erie every five years with the purpose of addressing data and knowledge gaps necessary to management agencies and the Lake Erie LaMP. LEBS deepwater science capabilities also provided a platform for data collection by Lake Erie investigators from multiple agencies and universities including: the USGS GLSC, ODW, KSU, OSU, UM, PU, UT, and the USNRL. Samples from this survey are being processed and a separate report of the findings will be made available in a separate document. Our 2014 vessel operations were initiated in mid-April, as soon after ice-out as possible, and continued into early December. During this time, crews of the R/V Muskie and R/V Bowfin deployed 196 bottom trawls covering 48.5 km of lake-bottom, nearly 6 km of gillnet, collected data from 60 hydroacoustics transects, 285 lower trophic (i.e., zooplankton and benthos) samples, and 330 water quality measures (e.g., temperature profiles, water samples). Thus, 2014 was an intensive year of field activity. Our June and September bottom trawl surveys in the Western Basin were numerically dominated by Emerald Shiner, White Perch, and Yellow Perch; however, Freshwater Drum were dominant by biomass. Age-2+ Yellow Perch and White Perch diets from our western basin trawl had highest occurrences of benthic invertebrates in spring and fall. Hexagenia spp. accounted for >25% of Yellow Perch and White Perch diet composition (dry weight) in spring. We conducted an analysis using data from the past 6 years of our East Harbor survey to determine to what degree our new research vessel and trawl is affecting our ability to detect trends across the 50+ year time series. We also evaluated trends in water temperatue, dissolved oxygen, secchi depth and total Phosphorus from our LTLA sites near Vermilion, Ohio. Within the following report sections, we describe specific results from our primary surveys conducted in 2014.

Report↗
USGS2014

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2013

In 2013, the U.S. Geological Survey’s Lake Erie Biological Station successfully completed large vessel surveys in all three of Lake Erie’s basins. Lake Erie Biological Station’s primary vessel surveys included the Western Basin Forage Fish Assessment and East Harbor Forage Fish Assessment as well as contributing to the cooperative multi-agency Central Basin Hydroacoustics Assessment and the Eastern Basin Coldwater Community Assessment (see Forage Task Group and Coldwater Task Group reports, respectively). Further large vessel sampling included individual research data collection as well as assisting with University (e.g., University of Toledo) and agency (e.g., USFWS, USEPA) large vessel sampling needs. Our 2013 vessel operations began on April 4th and concluded on November 21 with a total of 77 large vessel sampling days (83 total days). During this time, crews of the R/V Muskie and R/V Bowfin deployed 174 trawls covering 147 km of lake-bottom, over 13 km of gillnet, collected hydroacoustic data that extended over 250 km of the central and eastern basins, and approximately 180 collective zooplankton, benthos, and water samples. 2013 was the first complete sampling year using the R/V Muskie. Technologies available on the new platform provided opportunities for LEBS to improve data sampling methods and results. An investment was made in mensuration gear for the trawls. This gear is attached to the trawl’s headrope, footrope, and wings; thus, allowing measurement of the area swept and conversion of catches to densities. Another improvement included real-time output of water parameter sonde profiles (e.g., temperature, dissolved oxygen). The ability to view profile data on a tablet allowed quick identification of thermoclines as well as the presence (or absence) of hypoxia. Minor modifications were made to survey designs relative to last year (see 2013 report), and thus, collection of long-term data from the R/V Muskie has commenced. One minor change was that we are now indexing yellow perch maturation data during our fall trawl surveys in response to a request from the Lake Erie Yellow Perch Task Group. Within the following sections, we describe results from our 2013 sampling efforts in Lake Erie.

Report↗
USGS2009

Ages and lengths of yellow perch Perca flavescens , white perch Morone americana , and lake whitefish Coregonus clupeaformis in commercial trap nets in western Lake Erie

We collected samples of yellow perch (Perca flavescens) and white perch (Morone americana) in spring, and of lake whitefish (Coregonus clupeaformis) in autumn, from commercial trap nets set in western Lake Erie in 2008. The yellow perch sample (N = 153) was dominated (72%, of the total sample) by the 2003 year class, followed by the 2005 year class (12%). The white perch sample (N = 201) was dominated by the 2005 year class (39% of the total sample), followed by the 2003 year class (23%). The lake whitefish (N = 99) sample was dominated by the 2003 year class (75%) followed by the 2001 year class (10%). For yellow perch (both sexes in spring, analyzed separately) and lake whitefish (males in autumn), mean total length at age 5 was the same for the 2001 year class (calculated from historical data) and the 2003 year class.

Lake Erie↗
USGS2009

Surveillance and status of fish stocks in western Lake Erie, 2008

The Lake Erie Biological Station has conducted bottom trawl assessments of fish populations in western Lake Erie near East Harbor State Park, Ohio each summer and autumn since 1961. The catches of most age-0 forage fishes in 2008 were less than their 15-year means. Mean densities for five species exceeded the long term mean. Mean density of age-0 white perch Morone americana was more than double last year’s mean and the long-term mean. Densities of both yellow perch Perca flavescens and walleye Sander vitreus were at or above their long term mean. Catches of round goby Neogobius melanostomus (all ages combined) exceeded the previous five years, but were substantially below the species’ 13-year (1996-2008) mean. For five species, mean total lengths of age-0 individuals captured in 2008 were greater than their respective 20-year means. During 1988-2007, the frequency of occurrence for yellow perch diet items was highest for benthic invertebrates and zooplankton during the summer and benthic invertebrates in autumn. During summer zooplankton and benthic invertebrates were frequently consumed by white perch. Benthic prey for white perch occurred more frequently in the last 5-10 years.

Lake Erie↗