Publications

A simulation model of lake trout Salvelinus namaycush (Walbaum 1792) population dynamics in Lake Pend Oreille, Idaho, was used to estimate (1) the optimal allocation of effort among gillnet mesh sizes that minimizes abundance in the shortest time; (2) the number of years needed to suppress the population to 90% of peak abundance; and (3) once suppressed, how much effort could be reduced...

In general, fish residing in rivers differ from fish residing in lakes in their mercury (Hg) isotope ratios. Specifically, fish residing in lakes typically show enriched values for the isotope ratios of δ202Hg (mass-dependent fractionation of isotope 202Hg) and Δ199Hg (mass-independent fractionation of isotope 199Hg) compared with fish residing in rivers, because photochemical effects...

Ichthyoplankton communities are dynamic and vary spatiotemporally based on factors such as wind, water currents, and phenology. Nonetheless, ichthyoplankton are an indicator of spawning success in fish populations and examining their community diversity and composition can serve to provide information on ecosystem integrity. Although some ichthyoplankton species may be transient...

Co-occurrence of environmental stressors is ubiquitous in ecosystems, but cumulative effects are difficult to predict for effective indicator development. Individual stressors can amplify (synergies) or lessen (antagonisms) each other's impacts or have fully independent effects (additive). Here we use the Laurentian Great Lakes, where a multitude of stressors have been studied for...

Under certain conditions, polychlorinated biphenyl (PCB) concentration in individuals of one sex of an adult fish population may exceed that of the other sex by more than a factor of two. This phenomenon, known as the PCB hot spot effect, has been postulated to be contingent upon the following two conditions: (1) presence of a PCB hot spot in the bottom sediments of the aquatic ecosystem...

Stock assessments of Walleyes Sander vitreus in Lake Erie rely on a combination of suspended and bottom overnight gill‐net surveys to provide population and demographic information. However, the assumption that Walleyes undertake diel vertical migrations and become available to the suspended gill nets at night has never been validated. To understand how vertical habitat use affects the

Climate change effects are already significant, but can also magnify other ecological problems. This can be clearly seen in the Laurentian Great Lakes, which have suffered habitat degradation, fishery overharvest and dramatic alterations by invasive species. Thermal changes are expected to cause extensive loss of suitable fish habitat, and changing precipitation patterns will aggravate...

Stock assessments are critical to modern fisheries management, supporting the calculation of key reference variables used to make informed management decisions. However, there is still considerable uncertainty as to which class of assessment models is appropriate to use under different circumstances. A common class of models used when age data are available are statistical catch-at-age...

Significant Findings for Year 2017: 1) Offshore spring total phosphorus (TP) in 2017 was 4.4 µg/L; values remained stable since 2001. Offshore soluble reactive phosphorus (SRP) remained low (1.1 µg/L) in 2017; Apr/May – Oct mean values have been stable in nearshore and offshore habitats since 1998 (range, 0.4 – 3.3 µg/L). Apr/May – Oct mean TP concentrations were low at both nearshore...

Collaborative Lake Ontario bottom trawl surveys, led by the United States Geological Survey (USGS), provide science and management information for evaluating Fish Community Objectives including predator-prey balance and prey fish community diversity. In 2018, the New York State Department of Environmental Conservation (NYSDEC), Ontario Ministry of Natural Resources and Forestry (OMNR)...

This report presents biomass-based summaries of fish communities in western Lake Erie derived from USGS bottom trawl surveys from 2013 to 2017 during June and September. The survey design provided temporal and spatial coverage that does not exist in the interagency trawl database, and thus complemented the August Ohio-Ontario effort to reinforce stock assessments with more robust data...

Scientists from the U.S. Geological Survey’s Great Lakes Science Center conducted integrated acoustic and mid-water trawl surveys of Lake Huron in 1997 and annually from 2004-2017. The 2017 survey was conducted during September and included transects in Lake Huron’s main basin, Georgian Bay, and North Channel. Mean lake-wide pelagic fish density was 1582 fish/ha and mean pelagic fish...