Geology topics

Solomon R. David

Publications and source records attributed to Solomon R. David.

4 recordsLinked to original sources

USGS2017

Report from the Workshop on Coregonine Restoration Science

Summary Great Lakes fishery managers have the opportunity and have expressed interest in reestablishing a native forage base in the Great Lakes consisting of various forms and species within the genus Coregonus . This report summarizes the proceedings of a workshop focused on a subset of the genus, and the term “coregonines” is used to refer to several species of deepwater ciscoes (also known as “chubs”) and the one more pelagic-oriented cisco species ( Coregonus artedi , also known as “lake herring”). As the principal conservation agency for the United States Government, the Department of Interior has unique and significant authorities and capacities to support a coregonine reestablishment program in the Great Lakes. To identify and discuss key uncertainties associated with such a program and develop a coordinated approach, the U.S. Geological Survey (USGS) and the U.S. Fish and Wildlife Service (FWS), the principal Department of the Interior bureaus to address Great Lakes fishery issues, held the first of a series of workshops on coregonine science in Ann Arbor, Michigan, on October 11–13, 2016. Workshop objectives were to identify (1) perceived key uncertainties associated with coregonine restoration in the Great Lakes and (2) DOI capacities for addressing these key uncertainties.

Open-File Report↗

USGS2014

Laboratory estimation of net trophic transfer efficiencies of PCB congeners to lake trout (Salvelinus namaycush) from its prey

A technique for laboratory estimation of net trophic transfer efficiency (γ) of polychlorinated biphenyl (PCB) congeners to piscivorous fish from their prey is described herein. During a 135-day laboratory experiment, we fed bloater ( Coregonus hoyi ) that had been caught in Lake Michigan to lake trout ( Salvelinus namaycush ) kept in eight laboratory tanks. Bloater is a natural prey for lake trout. In four of the tanks, a relatively high flow rate was used to ensure relatively high activity by the lake trout, whereas a low flow rate was used in the other four tanks, allowing for low lake trout activity. On a tank-by-tank basis, the amount of food eaten by the lake trout on each day of the experiment was recorded. Each lake trout was weighed at the start and end of the experiment. Four to nine lake trout from each of the eight tanks were sacrificed at the start of the experiment, and all 10 lake trout remaining in each of the tanks were euthanized at the end of the experiment. We determined concentrations of 75 PCB congeners in the lake trout at the start of the experiment, in the lake trout at the end of the experiment, and in bloaters fed to the lake trout during the experiment. Based on these measurements, γ was calculated for each of 75 PCB congeners in each of the eight tanks. Mean γ was calculated for each of the 75 PCB congeners for both active and inactive lake trout. Because the experiment was replicated in eight tanks, the standard error about mean γ could be estimated. Results from this type of experiment are useful in risk assessment models to predict future risk to humans and wildlife eating contaminated fish under various scenarios of environmental contamination.

Journal of Visualized Experiments↗

USGS2012

Effects of activity and energy budget balancing algorithm on laboratory performance of a fish bioenergetics model

We evaluated the performance of the Wisconsin bioenergetics model for lake trout Salvelinus namaycush that were fed ad libitum in laboratory tanks under regimes of low activity and high activity. In addition, we compared model performance under two different model algorithms: (1) balancing the lake trout energy budget on day t based on lake trout energy density on day t and (2) balancing the lake trout energy budget on day t based on lake trout energy density on day t + 1. Results indicated that the model significantly underestimated consumption for both inactive and active lake trout when algorithm 1 was used and that the degree of underestimation was similar for the two activity levels. In contrast, model performance substantially improved when using algorithm 2, as no detectable bias was found in model predictions of consumption for inactive fish and only a slight degree of overestimation was detected for active fish. The energy budget was accurately balanced by using algorithm 2 but not by using algorithm 1. Based on the results of this study, we recommend the use of algorithm 2 to estimate food consumption by fish in the field. Our study results highlight the importance of accurately accounting for changes in fish energy density when balancing the energy budget; furthermore, these results have implications for the science of evaluating fish bioenergetics model performance and for more accurate estimation of food consumption by fish in the field when fish energy density undergoes relatively rapid changes.

Transactions of the American Fisheries Society↗

USGS2012

Absence of fractionation of mercury isotopes during trophic transfer of methylmercury to freshwater fish in captivity

We performed two controlled experiments to determine the amount of mass-dependent and mass-independent fractionation (MDF and MIF) of methylmercury (MeHg) during trophic transfer into fish. In experiment 1, juvenile yellow perch ( Perca flavescens ) were raised in captivity on commercial food pellets and then their diet was either maintained on unamended food pellets (0.1 μg/g MeHg) or was switched to food pellets with 1.0 μg/g or 4.0 μg/g of added MeHg, for a period of 2 months. The difference in δ 202 Hg (MDF) and Δ 199 Hg (MIF) between fish tissues and food pellets with added MeHg was within the analytical uncertainty (δ 202 Hg, 0.07 ‰; Δ 199 Hg, 0.06 ‰), indicating no isotope fractionation. In experiment 2, lake trout ( Salvelinus namaycush ) were raised in captivity on food pellets and then shifted to a diet of bloater ( Coregonus hoyi ) for 6 months. The δ 202 Hg and Δ 199 Hg of the lake trout equaled the isotopic composition of the bloater after 6 months, reflecting reequilibration of the Hg isotopic composition of the fish to new food sources and a lack of isotope fractionation during trophic transfer. We suggest that the stable Hg isotope ratios in fish can be used to trace environmental sources of Hg in aquatic ecosystems.

Environmental Science & Technology↗