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CONFERENCE SCHEDULE UPDATES & CHANGES: As a result of the prolonged government shutdown, we experienced a number of cancellations and changes to the schedule. Cancellations and changes are listed here (as of January 26, 2019). 

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T14: Fisheries: Great Lakes II [clear filter]
Tuesday, January 29

10:20am EST

(FISHERIES: GREAT LAKES 2) Evaluating the Influence of Past and Current Environments on Lake Erie Walleye Growth Rates
AUTHORS: L. Zoe Almeida, Ohio State University; Matthew D. Faust, Ohio Department of Natural Resources, Division of Wildlife; Stuart A. Ludsin, Ohio State University; Elizabeth A. Marschall, Ohio State University

ABSTRACT: Growth rates of animals are often assumed to be a response to recent environmental conditions; however, there is increasing evidence from numerous organisms that growth in one year may also be reflective of environmental conditions experienced earlier in life. Therefore, large-scale stressors, such as eutrophication and climate change may affect individuals immediately and latently, which is rarely considered in the management of exploited populations. Herein, we examined the factors that may influence growth rates of Lake Erie walleye (Sander vitreus), a system exposed to eutrophication and climate change. We used data from annual fall gillnet surveys (1978-2015) to characterize median size-at-age of individual annual cohorts in response to changes in physical conditions (e.g., temperature) and the food web (e.g., prey availability) during early life (= age-2), which may have arisen due to eutrophication and climate change (i.e., warming and increased precipitation). We hypothesized that environmental conditions in the current year, growth rates during early-life (as a reflection of early-life environmental conditions), and growth rates in the previous year (as a reflection of recent growth) would affect age-specific annual growth rates. We performed preliminary linear mixed model analyses with the median size within cohorts at age-2 representing early life growth, median growth rate in the previous year, and annual average temperatures. Using a model selection approach, no combination of these factors was better able to predict growth rates than the null model. However, we still need to test for effects of age-0 growth on growth rates later in life and for other environmental effects on growth, including annual cumulative degree days, prey-fish availability, and walleye population size. Our analyses will assist Lake Erie fisheries managers by assessing the relative importance of early-life versus contemporary growth conditions on recent growth performance.

Tuesday January 29, 2019 10:20am - 10:40am EST

10:40am EST

(FISHERIES: GREAT LAKES 2) Density-Dependent and Independent Effects on Walleye Harvest in Lake Erie
AUTHORS: David Dippold, The Ohio State University; Grant Adams, University of Washington; Stuart Ludsin, The Ohio State University

ABSTRACT: Both density-dependent and density-independent factors can affect the harvest of exploited fish populations. For instance, inter-annual variation in temperature could modify the timing and spatial extent of fish migrations, and in turn, fishery catches. However, this relationship could be mediated by density-dependent factors, if for example, high fish abundance leads to widespread habitat use that reduces the effects of temperature on migration and subsequent harvest. Toward understanding the relative influence of these factors on fishery harvest, we quantified the relationship among temperature, population size, and the temporal and spatial distribution of walleye (Sander vitreus) recreational harvest in Lake Erie during 1990-2015. Knowing that adult walleye migrate eastward from the western basin during spring and summer towards cooler temperatures, we hypothesized that: 1) years with higher spring and summer temperatures would be accompanied by reduced catches in the western basin relative to the deeper, cooler central and east basins; 2) walleye catches in the central and eastern basins would occur earlier during the spring/summer in warmer (relative to cooler) years; and 3) these relationships would be more apparent in years of low population size because in years of high abundance, walleye (especially young adults) would continue to reside in the west basin throughout the summer. To test our hypotheses, we constructed and compared variable coefficient generalized additive models, which used spatially-explicit (10x10 min grids) recreational catch and effort information, as well as temperature, bathymetric, and lake-wide abundance data. Beyond discussing the role of temperature and total abundance in driving spatiotemporal patterns in walleye harvest, we discuss the implications for fisheries management under a changing climate.

Tuesday January 29, 2019 10:40am - 11:00am EST

11:00am EST

(FISHERIES: GREAT LAKES 2) You Can't Just Use Gold: The Effects of Elevated Algal and Sedimentary Turbidity on Lure Success for Walleye (Sander vitreus)
AUTHORS: Chelsey L. Nieman, Suzanne M. Gray – The Ohio State University

ABSTRACT: Increasing anthropogenic turbidity changes underwater visual environments, leading to altered perception of visual cues. This alteration may have a variety of consequences, such as movement to other localities, a shift in diet or preferred prey, and reduced consumption of prey items. Lures are known to be perceived by fish as a potential prey item, therefore lure color/type can be utilized as a relative proxy for prey items that fish are capable of visually perceiving in turbid water. The objective of this study was to understand how shifts in visual environments may influence predatory success of Walleye (Sander vitreus) in Lake Erie using both local knowledge of altered fishing practices as well as lure success. Charter boat captains on Lake Erie are experienced in fishing in and around algal blooms and as such their knowledge and real-time lure success data allowed us to monitor color of lures that were successful in attracting Walleye under differing conditions. A survey of Lake Erie charter captains (N=37, 38% response rate) was used to determine how altered water quality (i.e. algal blooms) affected fishing practices and lure usage over the long term, with results indicating that lure color success changed in highly turbid water. Additionally, a mobile phone application, Walleye Tracker, was used by 19 charter captains over two years to gather real time data on lure successes. The use of photographs of lures and water conditions allowed for quantitative, in situ, analysis of lure successes in differing water clarity conditions. The results of this study indicate that increases in both sedimentary and algal turbidity that are altering the underwater visual environment are not only changing visual perceptions of Walleye, but also indicate that this is likely to have long-term consequences, not only for the ecosystem, but also for recreational anglers within these altered systems.

Tuesday January 29, 2019 11:00am - 11:20am EST

11:20am EST

(FISHERIES: GREAT LAKES 2) Smallmouth Bass Population Characteristics in Chequamegon Bay, Lake Superior Under a Unique 22-inch Size Limit
AUTHORS: Dray Carl, Wisconsin Department of Natural Resources

ABSTRACT: Minimum length limits are the most commonly used regulation for protecting, enhancing, or manipulating black bass recreational fisheries, and most limits are generally set at appropriate lengths to provide harvest opportunities of larger individuals. However, in 1994, growth overfishing and angler outcry led fishery managers from the Wisconsin Department of Natural Resources (WDNR) to enact a 22-inch (559-mm) minimum size restriction on Smallmouth Bass in Wisconsin waters of Lake Superior. This regulation has essentially created a complete catch-and-release fishery for Smallmouth Bass, as no bass greater than 559 mm have been sampled in the field or observed in creel surveys during the 24-year period. Within Wisconsin waters of Lake Superior, Smallmouth Bass are largely localized to Chequamegon Bay, a 13,750-ha shallow (mean depth 8.5-m) embayment adjacent the Apostle Islands. I used time series data from standardized gillnet samples (3600’, graded mesh) and annual hook-and-line sampling to evaluate trends in population dynamics before and after the regulation change. I also evaluated Smallmouth Bass seasonal movement patterns in Chequamegon Bay using floy tag recapture histories. Immediately following the regulation, Smallmouth Bass size structure and abundance increased dramatically, presumably due to a large decrease in mortality. Overall, annual mortality is now 2.5 times lower than before the regulation change. However, growth remained constant throughout the time series data, suggesting adequate resources to support increased abundance of Smallmouth Bass in Chequamegon Bay. Results from this study provide an example of Smallmouth Bass population dynamic rates from a population suited for a “trophy” minimum length limit, information for adaptive management of Smallmouth Bass in northern climates, and numerous new questions for additional research. Potential community-level effects of increased Smallmouth Bass abundance in combination with an overall warming Lake Superior should be investigated.

Tuesday January 29, 2019 11:20am - 11:40am EST

11:40am EST

(FISHERIES: GREAT LAKES 2) Changes in Great Lakes Forage Species Abundance and Composition: 25 Years of Trawling on Lake St. Clair
AUTHORS: Jan-Michael Hessenauer, Andrew Briggs, Brad Utrup, Todd Wills – Michigan Department of Natural Resources

ABSTRACT: The Laurentian Great Lakes have experienced substantial ecological change over the past 25 years in response to the invasion of non-native species, changes in nutrient fluxes, habitat degradation, and restoration initiatives.  Long term datasets provide a valuable tool to assess the scale of broad ecological change and make predictions about future change in response to perturbation.  The Michigan Department of Natural Resources Lake St. Clair Fisheries Research Station conducts annual spring trawl surveys on Lake St. Clair, using an 8.4 m headrope otter trawl with 0.95 cm codmesh. This survey is part of a continuous monitoring program occurring since 1993 with the goal of assessing the status of the lakes forage fish community and corresponds with the establishment and dominance of dreissenid mussels (first detected in 1986) and Round Goby Neogobius melanostomus (first detected in 1990).  Each spring an index site is trawled for three 10-minute tows.  Captured fish for each tow are graded through a 3.2 cm sorting mesh to separate forage sized individuals from the rest of the catch.  Forage was identified, counted and weighed, and a subset of up to 150 individuals per species were measured for total length to generate length frequency data.  Using these data, we calculated indices of abundance and diversity for the forage fish community and compare trends in these data over the time series.  These data provide useful management benchmarks against which the response to ecological perturbations have on the forage fish community of the Great Lakes.

Tuesday January 29, 2019 11:40am - 12:00pm EST