Welcome to the interactive web schedule for the 2019 Midwest Fish & Wildlife Conference! Please note, this event has passed. To return to the main Conference website, go to: www.midwestfw.org.
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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).
The workshop aims at providing a hands-on experience for attendees to learn and use multilevel (or mixed effect) models using R, including, (1) a general overview of the linear multilevel modeling approach, (2) its applications, (3) its implementation in R (using R package lme4), (4) its implications in ecological applications, and (5) its expansion to modeling nonlinear and non-normal problems. The workshop will be largely based on Chapter 10 of Qian (2016), including examples from modeling stream ecosystem responses to watershed urbanization, statistical issues related to Toledo water crisis, detecting illegal poaching of endangered plant species in National Parks, modeling changes in Lake Erie nearshore fish community in response to shoreline changes, and setting nutrient criteria for lakes and streams. Attendees are encouraged to submit case studies ahead of the time to be included in the workshop. The workshop will discuss some important conceptual issues that are commonly encountered in applications, through the development of empirical Bayes methods and the Bayesian hierarchical models, as well as Stein's paradox in classical statistics. The discussion will help attendees to better recognize when multilevel modeling is appropriate.
Intended Audience: For graduate students and professionals with knowledge at the level of a graduate-level biostatistics course, including statistical inference using hypothesis testing and estimation, statistical modeling (linear and nonlinear regression), and a working knowledge of statistical programming language R.
Presenters: Dr. Song Qian, The University of Toledo
AUTHORS: Lydia R. Doerr, Dr. Patrick Forsythe, Dr. Christopher Houghton – University of Wisconsin-Green Bay; Scott Hansen, Wisconsin Department of Natural Resources; Dr. Kevin Pangel, Central Michigan University
ABSTRACT: Much remains unknown regarding the early life history of Lake Whitefish in the Great Lakes despite their ecological and economic importance. The capture of larval Lake Whitefish in four major Green Bay tributaries (Fox, Menominee, Peshtigo, and Oconto Rivers) indicates the re-establishment of potamodromous stocks and suggests that these tributaries contribute to the overall metapopulation. The collection of larvae from the Sturgeon Bay shipping canal and the other reefs throughout Green Bay provides evidence that Lake Whitefish are also spawning in nearshore habitats. The ability to identify natal origin of a specific population is essential to creating effective stock-specific management plans; capable of protecting various sub-population that make up the larger Lake Whitefish metapopulation. Larvae collected during 2017-2018 were used to examine whether otolith microchemistry can accurately determine natal origin of these individuals. Preliminary analyses found significant differences in the ratio of strontium and barium to calcium in riverine and offshore water chemistry for Green Bay and Lake Michigan. The incorporation of these and other trace elements in larval otoliths allowed for the identification of natal origins of Lake Whitefish sub-populations. Otolith microchemistry proved successful at delineating natal origins at both broader level (i.e. tributary vs. open water) and at the site-specific scale.
AUTHORS: Andrew Ransom, Dr. Patrick Forsythe, Dr. Chris Houghton – University of Wisconsin-Green Bay
ABSTRACT: A resurgence of the Lake Whitefish (Coregonus clupeaformis) population within the waters of Green Bay has been documented in recent years despite overall low and stable numbers reported for Lake Michigan. Furthermore, large numbers of adult Lake Whitefish have been observed within major tributaries during the time of spawning in late fall. While our understanding of the ecology and behavior of Lake Whitefish in Lake Michigan is improving, knowledge gaps exist with these new river spawning ecotypes. Among these knowledge gaps are microhabitat selection in spawning locations, as well as timing and drivers of migration. In order to bridge these gaps, we used using Adaptive Resolution Imaging Sonar (ARIS) to monitor relative fish abundances in 10 sample locations with different physical characteristics (ie. flow rates and substrate type) on the Fox (n=5) and Menominee (n=5) Rivers in Wisconsin. To confirm egg deposition in spawning locations, suction sampling was also conducted throughout each river. Sampling was conducted in November and December of 2017 and 2018, in order to encompass the entire spawn period. Results will be used to influence potential restoration efforts for similar ecotypes across the Great Lakes.
AUTHORS: Joseph D. Schmitt, Christopher S. Vandergoot, Richard T. Kraus – USGS Great Lakes Science Center, Lake Erie Biological Station
ABSTRACT: Populations of coldwater fishes such as burbot Lota lota, lake whitefish Coregonus clupeaformis, and lake trout Salvelinus namaycush have declined in Lake Erie, while cisco Coregonus artedi have been extirpated. Warming temperature regimes and the re-eutrophication of Lake Erie have increased the frequency of harmful algal blooms and hypoxic events, which can reduce oxythermal habitat availability. Using vertical profile data collected in the central basin from 2008-2017, we developed generalized additive models to explore spatial, seasonal, and interannual trends in oxythermal habitat availability for lake trout, cisco, lake whitefish, and burbot based on published oxythermal niche benchmarks. Habitat availability was usually temperature-limited rather than oxygen-limited, and significant (P<0.05) monthly and interannual variations in habitat availability were detected for most species. In general, oxythermal habitat was most limited during August and September; moreover, significant interannual trends in habitat availability were also detected, with 2016 having the most extreme habitat reduction for many species due to record high temperatures. Understanding the spatiotemporal dynamics of oxythermal habitat availability will be important for the conservation and restoration of these fishes in our changing climate. Moreover, these models can be integrated with climate predictions to better understand how warming temperatures will affect coldwater habitat in the future.
AUTHORS: Brad Utrup, Jan-Michael Hessenauer, Andrew S. Briggs, Todd Wills, Michael Thomas (retired) – Michigan Department of Natural Resources
ABSTRACT: Age estimation is a fundamental part of fisheries management; critical for evaluations of growth, mortality and recruitment. Validation of ages obtained from age estimation of hard structures is a necessary part of the ageing process in order to better understand the magnitude of error and bias associated with structure interpretation. Validation studies on large-bodied and long-lived species such as Lake Sturgeon Acipenser fulvescens are challenging. We utilized a 20-year mark-recapture dataset from Lake St. Clair and the St. Clair River, Michigan, USA to validate pectoral fin ray age estimates from 51 individuals that were sampled twice. The time at large ranged from 2 to 17 years between capture-recapture events. All fin rays were aged by two separate readers (agreement rate 94.1%). Samples were divided into four quartiles based on mean annual growth rates during their time at large. Age error was defined as the difference between the age of the fish at first and second capture and the number of years at large. No difference in time at large existed among the four groups, but age error differed among the four groups. Furthermore, age error did not differ from zero for the two fastest growing quartiles but did differ significantly from zero for the two slowest growing quartiles. We conclude that for Lake Sturgeon growing faster than 3 cm/year (generally less than 100 cm in TL) pectoral fin rays provide valid age estimates. Managers should consider the growth rates of Lake Sturgeon in their populations for determining a size threshold for utilizing fin rays for age estimation.
AUTHORS: Luke A. Bobay, L. Zoe Almeida, Elizabeth A. Marschall, Stuart A. Ludsin – The Ohio State University
ABSTRACT: A full understanding of how climate change affects the recruitment process of fish is lacking for most populations. The possibility exists that altered temperature and precipitation patterns could interact with other factors (e.g., photoperiod) to reduce the availability of zooplankton prey to pre-recruited individuals. If preferred prey sizes or taxa are unavailable during critical periods of development (e.g., larval stage), foraging success, growth, and survival might decline. As a first step toward understanding how climate variation influences larval yellow perch (Perca flavescens) success in Lake Erie, we processed the diets of larvae captured during spring 2017 from several nearshore areas of the western basin. While we expected average zooplankton prey size in the diet to increase with yellow perch size, we were uncertain as to how availability of prey of different sizes and taxa would affect which prey types are consumed. We also did not know if larval yellow perch require a specific size or type of prey during early life, when their ability to catch large, fast prey is limited. Preliminary analyses indicate that the biomass of yellow perch diets varied both through time and between sites (Date: ?<sup>2</sup><sub>4,428</sub>= 114.3, p < 0.001, Site: ?<sup>2</sup><sub>3,428</sub>= 22.7, p < 0.001), with no obvious effect of fish size (Length: ?<sup>2</sup><sub>1,428</sub>= 0.04, p = 0.84). Interestingly, we found that some small prey items (e.g., small Cyclopoida) were primarily consumed by small yellow perch larvae (5 – 9 mm), whereas other small taxa (e.g., Bosmina) were primarily consumed by larger larvae (13 – 18 mm). Future analyses should reveal if these differences in consumption between larvae of different size are due to prey availability or a preference for specific taxonomic groups. Ultimately, these results will direct our impending inter-annual examination of larval yellow perch diets in relation to environmental conditions.
AUTHORS: David G. Fielder, Michigan Department of Natural Resources
ABSTRACT: Saginaw Bay historically supported large Walleye and Yellow Perch populations and fisheries. Walleye diet from 1989 to 2002 was dominated by Clupeids (Gizzard Shad and Alewives). Alewives from the main basin of Lake Huron used the bay for spawning and nursery grounds. Alewives disappeared from most of the lake as a result of a profound foodweb paradigm change in 2003. Walleye diet in the bay has become more diverse with age-0 Yellow Perch now comprising a major component. Yellow Perch have exhibited good reproductive success but mortality between age-0 and age-1 is now routinely upwards of 95%, resulting in failed recruitment to the larger population. It appears that Saginaw Bay’s predator/prey dynamics depend on a predation buffer from main basin pelagic planktivores with Cisco historically playing that role. With Alewives largely extirpated and Cisco not recovered, a broken linkage may exist resulting in suppressed Yellow Perch population and fisheries. Fishery managers are commencing a Cisco restoration initiative in Central Lake Huron partly in hopes of addressing this situation.
AUTHORS: Daniel Isermann, Lucas Koenig, Daniel Dembkowski – Wisconsin Cooperative Fishery Research Unit; Iyob Tsehaye, Wisconsin Department of Natural Resources; Wesley Larson, USGS-Wisconsin Cooperative Fishery Research Unit; Scott Hansen, Steve Hogler; Tammie Paoli – Wisconsin Department of Natural Resources; Troy Zorn, Michigan Department of Natural Resources
ABSTRACT: Green Bay supports important fisheries for walleyes, lake whitefish, and yellow perch and these species likely interact in a variety of ways. A better understanding of these interactions is needed to guide management decisions. Specifically, there are concerns that high walleye abundance could negatively influence abundance of yellow perch and lake whitefish, primarily through predation. However, the prevalence of round gobies within the ecosystem may provide a predation buffer for yellow perch and lake whitefish. Moreover, the lake whitefish population in and around Green Bay is comprised of multiple genetic stocks. Consequently, if walleye predation on lake whitefish varies across time and space, this predation could affect certain whitefish stocks to a greater degree than others. To help address some of these uncertainties, our research objectives are to determine if: 1) lake whitefish and yellow perch represent important prey for walleyes in Green Bay; 2) diets of these three species vary spatially and temporally and if diet overlap among species is evident; 3) the extent of walleye predation is sufficiently high to influence recruitment potential of lake whitefish and yellow perch and 4) extent of walleye predation varies among individual stocks of lake whitefish. We are integrating an intensive assessment of diet composition for all three species with bioenergetic modeling and genetic stock identification to address our objectives. We will discuss the innovative experimental framework we are using to address these objectives and provide preliminary results of our diet analyses.
AUTHORS: Katie Kierczynski, Michigan State University; Brian Roth, Michigan State University; Ed Roseman, USGS Great Lakes Science Center; Robin DeBruyne, University of Toledo/USGS Great Lakes Science Center
ABSTRACT: Lake Huron has undergone dramatic changes in the past few decades. Introductions of non-native species have drastically altered the food web and nutrient pathways. In the mid-2000s, alewife collapsed closely followed by Chinook salmon. Since then, some native prey species (e.g. bloaters) and some invasive species (e.g. round goby) have increased in abundance. Populations of native predators walleye and lake trout have also increased substantially, but there are now questions regarding the sustainability of current predator populations as well as uncertainty regarding connections among food web members given changes in prey populations and shifts in productivity. Predator diets can be used as evidence that could shed light on the sustainability of the food web. However, the last angler-caught predator diet study in Lake Huron was conducted between 2009 and 2011 (Roseman et al. 2014). That study demonstrated increased reliance on round goby for lake trout and walleye, but Chinook salmon continued to be dependent on alewife despite their exceptionally low abundance. The goals of the present study are to investigate how predator-prey relationships have changed since the 2009-2011 study and to determine spatial patterns and temporal trends in diet composition. We hypothesize that a) consumption of round goby will have increased for native predators, b) consumption of bloaters will have increased for all predator species, c) Chinook salmon will continue to be dependent on alewife, and d) diets will be heterogeneous across space and time. This data will give managers a more thorough understanding of predator-prey interactions in Lake Huron, and will be used to update models used by managers to evaluate the sustainability of current predator levels and stocking strategies.
AUTHORS: Taaja R. Tucker, University of Toledo; Edward F. Roseman, Stephen C. Riley, Timothy P. O’Brien, Darryl W. Hondorp, Dustin A. Bowser, Scott A. Jackson – US Geological Survey
ABSTRACT: Rehabilitation efforts of lake trout (Salvelinus namaycush) in Lake Huron have resulted in increased recruitment and capture of young wild lake trout in annual bottom trawl surveys conducted by the U.S. Geological Survey. To better understand the spatial distribution and food habits of wild juvenile lake trout, we performed diet analyses on 311 of 343 fish captured in bottom trawls at six ports in Lake Huron during October/November 2008–2017. Lake trout ranged in size from 27 to 371 mm, representing approximately three age classes. Most of the fish (83%) were captured at 46–64 m depths at the two northernmost ports, typically below the thermocline. Mysis diluviana was the most prevalent diet item, found in 222 of 299 fish with non-empty stomachs (74%), followed by Bythotrephes longimanus (31%), and round goby (Neogobius melanostomus; 11%). Young-of-year lake trout (Mysis and Daphnia, while larger lake trout converted to mostly fish-based diets at age 2+. Compared to a previous diet analysis of young Lake Huron lake trout from 2004–2006, fish in the current study consumed more unique prey items (12 vs. 6) and fish species, although many of the lake trout in the current study were larger than those analyzed in the past (74–120 mm). While the variety of taxa consumed by young lake trout has increased since the last study period, the most commonly observed prey items after Mysis were nonnative taxa. Mysis remain an important early food for lake trout in Lake Huron.
AUTHORS: Benjamin Leonhardt, Purdue University; Benjamin Turschak, Michigan Department of Natural Resources; Austin Happel, Colorado State University; Sergiusz Czesny, University of Illinois, Illinois Natural History Survey; Harvey Boostma, University of Wisconsin-Milwaukee; Jacques Rinchard, SUNY-Brockport; Matt Kornis, U.S. Fish and Wildlife Service; Charles Bronte, U.S. Fish and Wildlife Service; Tomas Höök, Purdue University, Illinois-Indiana Sea Grant
ABSTRACT: Documenting trophic relationships in aquatic ecosystems can facilitate understanding of not only system processes, but also the potential responses of food webs to stressors. In Lake Michigan, the introduction of invasive species (e.g., zebra mussel, Dreissena polymorpha; quagga mussel, Dreissena bugensis; round goby, Neogobius melanostomus) and reduced nutrient loading has resulted in changes in nutrient dynamics and community composition over the past two decades. As a result, abundances of many forage fish have declined, including alewife (Alosa pseudoharengus) which have historically supported the five dominant salmonid species of Lake Michigan (brown trout, Salmo trutta; Chinook salmon, Oncorhynchus tshawytscha; Coho salmon, Oncorhynchus kisutch; lake trout, Salvelinus namaycush; rainbow trout, Oncorhynchus mykiss). With these ecosystem changes, there is uncertainty as to the extent of how different species of salmonids will transition to alternative prey items (e.g., round goby). We investigated the diet complexity of Lake Michigan salmonids by evaluating stomach content composition, diet diversity, and lengths of alewife consumed. Stomachs collected in 2015 and 2016 in Lake Michigan revealed that Chinook salmon almost exclusively consumed alewife and had a lower diet diversity compared to the other four species, which consumed round goby (brown trout and lake trout), aquatic invertebrates (Coho salmon), and terrestrial invertebrates (rainbow trout) in addition to alewife. Additionally, salmonid species appeared to consume the entire size range of alewife that were available to them despite year to year changes in alewife length availability. Due to their reliance on alewife, it is likely that Chinook salmon may be more negatively impacted than other salmonid species if patterns of alewife decline continue in Lake Michigan.
AUTHORS: Ben Turschak, Michigan Department of Natural Resources; Harvey Bootma, UW-Milwaukee; Chuck Bronte, U.S. Fish and Wildlife Service; Sergiusz Czesny, University of Illinois; Tomas Hook, Purdue; Matt Kornis, U.S. Fish and Wildlife Service; Ben Leonhardt, Purdue; Jacques Rinchard, SUNY-Brockport
ABSTRACT: In the past several decades, the Lake Michigan ecosystem has experienced significant changes at all levels of the food web including major declines in pelagic forage fish biomass. To some degree, loss of pelagic forage has been offset by the invasion of the benthic Round Goby. Several piscivorous species including Lake Trout, Brown Trout, and Burbot have taken advantage of this novel prey source while others such as Chinook and Coho Salmon continue to rely on Alewives and other pelagic forage. We explored the trophic structure, diet, and potential for niche overlap of Lake Michigan piscivores from 2014-2016 using stable C and N isotopes. To estimate diet proportions among species, Bayesian mixing models were used. Region and year were used as fixed effects with total length as a continuous covariate. Isotopic niche overlap was assessed by fitting Bayesian ellipses to the data and measuring overlap among species. Regional and interannual variability in trophic structure and diet with corresponding changes in niche overlap were observed. Greatest niche overlap corresponded with dependence on Alewife whereas predators that took advantage of other prey sources including Round Goby, and terrestrial invertebrates exhibited lower probability of niche overlap. Degree of overlap also appeared to decrease corresponding to availability of alternative prey sources or reduced alewife abundance.
AUTHORS: Dan Traynor, Shawn Sitar – Michigan Department of Natural Resources Marquette Fisheries Research Station; Ji He, Michigan Department of Natural Resources Alpena Fisheries Research Station
ABSTRACT: Lake trout are the dominant piscivore in the upper Great Lakes and are a major focus in fisheries management. Lake populations underwent catastrophic collapses in the middle of the 20th century but have recovered in Lake Superior due to diligent management actions. Recently, lake trout recovery has improved in Lake Huron and there are indications that Lake Michigan may be following suit. Although controls on fishing, sea lamprey suppression, and stocking of hatchery fish were instrumental in lake trout recovery, we pose that dietary flexibility also contributed to its success. We analyzed the diet of a broad size range of lean and siscowet lake trout from spring and summer gill net surveys conducted in southern Lake Superior and western Lake Huron during 2005-2016. In addition to categorizing prey items by taxa, we grouped prey items by habitat types to further describe dietary flexibility. We found that lake trout diet compositions were diverse in both lakes Superior and Huron. Generally, the diet of leans and siscowets in Lake Superior were similar. We observed ontogenetic diet shifts in both lean and siscowet lake trout with small fish feeding predominantly in the benthos expanding to the pelagic zone as fish grew larger. Progress in lake trout recovery in Lake Huron coincides with collapses in alewife abundance and declines in Chinook Salmon populations. We pose that lake trout success in rapidly changing ecosystems is partly due to its high dietary flexibility and declines in Great Lakes Chinook salmon are due to its strong reliance on pelagic prey such as alewife.
AUTHORS: Anne Scofield, Paris Collingsworth, Tomas Höök – Purdue University; David Bunnell, USGS Great Lakes Science Center; Aaron Fisk, University of Windsor Great Lakes Institute for Environmental Research; Tim Johnson, Ontario Ministry of Natural Resources; Brian Weidel, USGS Lake Ontario Biological Station
ABSTRACT: Natural stable isotope ratios of nitrogen (d<sup>15</sup>N) and carbon (d<sup>13</sup>C) have proven to be valuable tools for identifying basal energy sources for fish production and describing trophic complexity, but cross-lake comparisons of stable isotope data are often limited by challenges associated with standardizing study design and isotopic baselines. Over the past decade, a great number of resources have been invested to generate stable isotope data for the lower food web and prey fishes across all five of the Great Lakes through the bi-national Cooperative Science and Monitoring Initiative (CSMI), providing opportunities for robust cross-lake comparisons. In this study, we investigate differences in nearshore subsidies and trophic transfer efficiencies to prey fish across the productivity gradient observed in the Great Lakes, which range from eutrophic (western Lake Erie) to ultra-oligotrophic (e.g., Lake Superior). Using rainbow smelt as a case study, we examine the basal carbon sources and trophic positions of prey fish in the offshore regions of the five lakes. We also consider how differences in the densities on non-native species, such as dreissenid mussels, may affect resource distribution and energy flow to fishes. Quantifying how trophic structures in lakes differ across a productivity gradient can help elucidate the consequences of human actions such as nutrient management programs, fish stocking, and non-native species introductions.
AUTHORS: Tristan Tackman (Student); Dr. Ashely Moerke (Professor/Undergraduate Advisor); Jake Larsen (Graduate) – School of Natural Resources and Environment, Lake Superior State University
ABSTRACT: The St. Marys River is the only outflow of Lake Superior and feeds both Lake Michigan and Lake Huron. The river itself rears a majority of these lakes’ sports fishes by providing ample spawning grounds; these young fish rely on small macroinvertebrates for most of their growth in early years. The objective of this study was to quantify and compare the supply of drifting invertebrates from the main rapids and the hydropower canal in an effort to understand key food sources available for fishes in the river. To do so, two larval drift nets were set overnight in the rapids and canal to collect drifting invertebrates during the months of May and June 2016. For each date biomass was calculated asash free dry weight and density was calculated as number of invertebrates per 100m<sup>3</sup>. Densities were the highest for Hydropsychidae and Mysidae at both sites, andcomprised 18% (the remanding 82% being non-dominant taxa) and 9.5% in the rapids and 26.7% and 8.9% in the canal site. Although Mysidaedensities were higher than other taxa, Hydropsychidae contributed more biomass to the system in both sites during May and June of 2016. Additionally, total drift densities were 2.4 times higher in the canal site than the rapids, suggesting that the canal is a better source of invertebrates to the St. Marys River. The canal is likely drawing water from more offshore areas in Lake Superior, which may explain the higher numbers of drifting Mysids in the canal site compared to the rapids.
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.
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.
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.
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.
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.
AUTHORS: Kishore Gopalakrishnan, Donna Kashian, Anna Boegehold, Nick Johnson – Wayne State University
ABSTRACT: Dreissenid mussels are successful invaders in a wide variety of freshwater environments. As biofoulers, they create serious economic and recreational problems. In addition, these rapid filter feeders alter their invaded ecosystem by disrupting the entire food web. Their rapid colonization rate and environmental resilience make them difficult to control. Many management options have been explored for combating the spread of dreissenid mussels, but an effective management strategy is elusive. In an effort to identify a novel management tool, we investigated the impacts of cyanobacteria, commonly associated with Harmful Algal Blooms (HABs), on reproduction in dreissenid mussels. Mussel populations may be regulated by HABs through several reproductive mechanisms including spawning and fertilization. Specifically we tested the impacts of several bloom forming cyanobacterial species on quagga mussel reproduction through a series of bioassays examining quagga mussels’ spawning, fertilization and sperm motility. Mussel were induced to spawn using serotonin, then the effect of five cyanobacterial species spawning and sperm motility was examined. Sperm motility was determined by recording the movement of sperm from five males per treatment at 400X, tracking velocity and distance travelled. Fertilization success was determined through assays combining quagga mussels’ egg and sperm in individual vials containing cyanobacteria species cultures (n=5), and enumerating zygote formation marked by cellular cleavage. Some cyanobacteria species inhibited reproductive endpoints; spawning was inhibited by Microcystis wesenbergii and M. ichthyoblabe, sperm motility was reduced by Aphanizomenon flos-aquae and two strains of M.aeruginosa and fertilization ratio decreased with exposure to five unique species of cyanobacteria including two strains of M. aeruginosa. These results show the HABs may negatively impact dreissenid populations. Determining the class of compounds and understanding the mechanism by which the cyanobacteria disrupts reproduction may inspire new dreissenid control tactics.
AUTHORS: David Hammond, Ph.D., Earth Science Laboratories, Inc.;Gavin Ferris, M.S., Solitude Lake Management, Inc.
ABSTRACT: In 2017 Earth Science Labs, Inc. designed and supervised a treatment protocol to eradicate invasive quagga mussels from the lake at Billmeyer Quarry in Pennsylvania. The treatment consisted of 3 separate applications of a liquid formulation of ionic copper called EarthTec QZ, delivered over a period of 37 days. Mussel mortality was determined through use of caged adult mussels that were suspended at different locations and depths throughout the lake. Mussels began to die within 3 days of the initiation of treatment, particularly in the top 20 feet of the water body. The death of the last caged mussel was confirmed 40 days after the initiation of treatment, in a cage that had been placed at a depth of 30 feet below the surface. Both biological and physicochemical data collected during the treatment period revealed that there was a pronounced thermocline at 25-35 foot depth. Such stratification is historically typical for this lake. The layer of water in the thermocline resisted mixing, which explains why mussels located above and below the thermocline were eradicated quickly, yet those within the thermocline required targeted treatment techniques and 40 days to succumb to 100% mortality. Microscopic analysis of plankton tows and visual inspection of the shoreline after partial pump-down of the quarry in early November indicated that all veligers and adults were successfully exterminated. Analysis of eDNA taken in December 2017 also suggests the eradication was complete. The cumulative sum of copper applied throughout the entire course of treatment totaled 0.44 mg/L – noteworthy because it is less than half the concentration EPA allows (1.0 mg/L) in a single algaecide treatment. The authors are cautiously optimistic that this is the first recorded instance of eradicating quagga mussels from an entire lake.
AUTHORS: Todd Severson, James Luoma, Jeremy Wise, Matthew Barbour – US Geological Survey
ABSTRACT: Because zebra mussels (Dreissena polymorpha) continue to spread through inland lakes and rivers of North America somewhat undeterred, the need to develop tools to control their populations has become a major research effort. Developing data regarding the impacts of water temperature and exposure duration on the toxicity of chemical molluscicides to zebra mussels will assist resource managers to select a treatment regimen with the greatest potential for successful eradication. We evaluated the toxicity of two EPA-registered (EarthTec QZ and Zequanox) and two nonregistered (potassium chloride and niclosamide) zebra mussels toxicants over a range of water temperatures and exposure durations. We evaluated each toxicant in replicated laboratory studies conducted at 7, 12, 17, and 22°C using exposure durations ranging from 8 hours to 14 days. The minimum lethal concentration of toxicant(s) and the exposure duration required to achieve complete zebra mussel mortality at each test temperature will be presented.
AUTHORS: Joel G. Putnam, Diane Waller, Justine Nelson– US Geological Survey Upper Midwest Environmental Sciences Center; Tammy J. Clark, Viterbo University
ABSTRACT: The search for new chemical controls for aquatic invasive species (AIS) that are efficacious and selective is needed to expand the arsenal of AIS control tools for resource managers. Chemical control options for dreissenid mussels (Dreissena polymorpha and D. bugensis) currently rely heavily on molluscicides that can be costly and/or harmful to nontarget species. The Environmental Protection Agency ECOTOX Knowledgebase was used to gather toxicity data for over 400 taxa covering five kingdoms and 7700 chemicals. Our search used structural activity relationships (SARs) to correlate chemical information with biological activity and predict new chemicals that are effective against dreissenid mussels. A database of chemical descriptors, such as molecular weight, solubility, and polar surface area, was created and published to link the chemical structure/information with species-specific toxicity. Toxicity trials have been initiated using a category of chemicals with high selective toxicity towards dreissenid mussels. Chemicals that produced significant mortality of dreissenid mussels were also tested on nontarget native freshwater mussels to determine selectivity. The results of toxicity trial will be combined with chemical characteristics (e.g., solubility) to identify toxicants that may be suitable for incorporation into a microparticle that is ingested by dreissenid mussels.
ABSTRACT: Zequanox molluscicide, a biological control for invasive dreissenid mussels, has been available for commercial use in enclosed and open water systems for approximately six years. During this time, the product has undergone development and been strategized for a variety of applications and markets. The product was recently trialed in Florida on Mytilopsis leucophaeata, with enough activity to warrant further experimentation. A biobox demonstration trial has been conducted at a hydroelectric generating station in Spain, the first trial of Zequanox in the EU. Furthermore, recently developments in fermentation has led to reduced product costs, and treatment strategies continue to be optimized with dose and hold and low dose maintenance programs being implemented. MBI looks forward to continuing collaboration on product development for use in enclosed water systems, as well as looking to optimize the product for open water applications, including development of a slow release granule or encapsulated formulation.
AUTHORS: Matthew T. Barbour, James A. Luoma, Todd J. Severson, Jeremy K. Wise – US Geological Survey
ABSTRACT: Zequanox® is an EPA-registered molluscicide for controlling populations of dreissenid mussels (zebra and quagga mussels). Zequanox® has demonstrated selective toxicity to dreissenid mussels. However, recent research indicates Zequanox can impact body condition and even cause mortality in non-target species. We assessed the avoidance behavior of two species each of cold-, cool-, and warm-water fish (lake trout, brook trout, lake sturgeon, yellow perch, and fathead minnow) to Zequanox® at the maximum concentration allowed by the product label (100 mg A.I./L). Naïve, juvenile fish were individually (n = 30) observed in a two-current choice tank through which treated and untreated water flowed simultaneously on either side. Each individual fish was observed during a control period (20 min) with no treatment and two treatment periods (20 min each) between which the treated side was alternated to eliminate bias. Positional data was collected and tabulated in real time with EthoVision® XT software. Zequanox® concentrations and water quality (pH, dissolved oxygen, temperature, and specific conductance) were monitored during each trial. Results from this research will help inform resource managers of the likelihood of fish to avoid Zequanox® treated areas, thereby assisting in the establishment of treatment-related risk assessments.
AUTHORS: Erika Jensen, Great Lakes Commission; Sandra Morrison, U.S. Geological Survey; Ceci Weibert, Great Lakes Commission
ABSTRACT: The Invasive Mussel Collaborative is working to advance scientifically sound technology for invasive mussel control to produce measurable ecological and economic benefits. The Collaborative provides a framework for communication and coordination and is identifying the needs and objectives of resource managers; prioritizing the supporting science, implementing communication strategies; and aligning science and management goals into a common agenda for invasive mussel control. The founding members of the collaborative are the U.S. Geological Survey, Great Lakes Commission, National Oceanic and Atmospheric Administration and the Great Lakes Fishery Commission. The Great Lakes Commission provides coordination and neutral backbone support for the collaborative. A broad membership base of states, provinces, tribal and other entities and a well-organized communication network facilitates the exchange of information between scientists, managers, and stakeholders. Strong connections with other regions outside the Great Lakes are in place to provide opportunities to share lessons learned. The Collaborative maintains a robust communication network to facilitate information-sharing on priority issues related to management and control of dreissenid mussels. The Collaborative also develops products and tools to support and advance management activities and will soon finalize a regional strategy to advance zebra and quagga mussel management for the Great Lakes region. This presentation will provide an update on these efforts.
ABSTRACT: The Bureau of Reclamation oversees water resource management in the western United States and is responsible for the operation of diversion, delivery, storage and hydropower facilities. The first detection of invasive dreissenid mussels in the western United States was in the Lower Colorado River in 2007. Hydropower facilities along the Colorado River have experienced operational impacts related to the presence of the mussels, including unplanned outages, overheating of critical systems, and increased maintenance. Reclamation is actively involved in the development and examination of a variety of control methods to reduce the impacts of invasive mussels in Reclamation managed waters and hydropower facilities. Development of passive and environmentally responsible methods for mussel settlement prevention on critical structures at hydropower facilities has been the focus of the research. Methods examined for settlement prevention in generator cooling systems include ultra-violet light, turbulence, laser-pulsed pressure, and carbon dioxide. The durability and effectiveness of anti-fouling and foul-release coatings have been extensively examined for use on equipment such as trash racks and fish screens. Centrifugal separation and self-cleaning strainers and filtration are being examined for shell debris mitigation. Reclamation is also currently involved in several research projects designed for mussel eradication in open water including biocontrol agent identification, genetic control methods, and potash. Additionally, Reclamation is planning to peruse the winning solution resulting from the recent crowdsourcing prize challenge designed to elicit theoretical solutions for the eradication of invasive mussels in open water.
ABSTRACT: Dreissena mussels pose a significant challenge to infrastructures. One key element contributing to this challenge is the lack of a practical method for large-scale control of populations once they become established throughout a water body. As a result, facilities drawing water from such water bodies are subjected to constant reinfestation. Although concerns exist about environmental impacts of molluscicides, it is the prohibitive total project cost of open-water control programs that currently eliminates them as a mitigation option. Total project cost includes not only the molluscicide and its application throughout the entire water body, but also a myriad of other expenses often required in the overall control program, such as fund raising, administration, regulatory approval, post-treatment mussel mortality monitoring, report writing, etc. The research project reported herein offers a potential solution to this seemingly intractable problem of prohibitively high control program expense. The key to the low cost of this proposed control approach is that it does not require treatment of the entire water body. In contrast to traditional control programs: 1) only a minuscule portion of the infested water body’s volume would be treated (“seeded”) with the control agent; and 2) the control agent would subsequently amplify itself and self-spread throughout the water body. There is only one type of control agent capable of doing that – a live one, a biological control agent. This presentation describes the research conducted in the first year of a multi-year project to find such a control agent. The project is based in Eurasia and specifically designed to find a hypervirulent (i.e., extremely lethal), highly-specific dreissenid parasite that one day (following years of comprehensive environmental safety studies) would be introduced into North American water bodies where it will leave a trail of dead dreissenids in the path of its spread.
AUTHORS: Kevin R. Keretz; Richard T. Kraus, Joseph Schmitt – US Geological Survey
ABSTRACT: Ecological and societal impacts of dreissenid mussels (Dreissena spp.) on Great Lakes ecosystems are well documented, and a better understanding of the mechanisms that cause variation in mussel abundance is needed. An outstanding question is how much mussel biomass is consumed by predation. To date, attention has mainly been focused on invasive Round Goby (genus species) predation of mussels. We note that the biomass of native mussel consumers, such as Freshwater Drum (Aplodinotus grunniens), may exceed Round Goby biomass by an order of magnitude in some areas. Thus, the role of predation on mussel population dynamics may be greater than is currently assumed. A significant difficulty for investigating mussel consumption by native predators is that mussels in stomachs are often a macerated mix of crushed shell and flesh. This prevents counting and measurement of individual prey items as is often performed in diet studies. Here, we develop an analysis to convert the crushed shell and flesh mixture found in diets of Freshwater Drum to a simple dry weight of mussel flesh. We then estimate daily ration as a first step in understanding the impact of Freshwater Drum on mussel populations in Lake Erie. Our results support evaluation of proposed mussel control methods by improving our knowledge of ecological mechanisms that influence mussel abundance.
AUTHORS: Lewis Steven Beckham, Barnacle-Blocker, LLC
ABSTRACT: The efficacy in situ of Mussel Stopper®, a brand name for a water insoluble, non-toxic, patented (10,053,584B1), US EPA labeled (89825-1) repellent for Dreissena mussels that can be applied underwater is being measured in a multi-location, multi-year randomized testing program. Testing apparatus consists of a PVC frame with six treatment sets of black ABS plastic coupons attached with cable ties. The ABS plastic coupons have one smooth side and one textured side. Treatments are untreated, component wax only and Mussel Stopper® applied according to labeled directions. The test lattices are suspended in the water column in locations picked for high incidence of Dreissena mussels. The tests are periodically lifted out of the water and visually rated for percent coverage by the mussels. Since each test has two sides, a total of twelve replications per location are evaluated. After two years of testing, Mussel Stopper® treated coupons averaged 0.60% covered. Component wax only treated coupons averaged 17.7% covered and untreated coupons have averaged 84.8% coverage. Standard deviation is 38.4%. Testing continues, but so far Mussel Stopper® performance is significantly better than the checks.KEY WORDS: Mussel Stopper, Dreissena mussels, applied underwater, US EPA labeled, non-toxic, water insoluble
AUTHORS: Stephen M. Tyszko, Jeremy J. Pritt, Joseph D. Conroy –Ohio Division of Wildlife
ABSTRACT: Using standard sampling methods for sport fish assessment allows powerful comparisons across time and space, if sample size is adequate. Biologists have begun evaluating precision and catch of sport fish surveys using North American standard methods (NASM) and have used resample methods to estimates sample sizes required to meet precision and catch objectives. The Ohio Division of Wildlife has collected standard sport fish surveys since 2003, providing an opportunity to further understand the performance of these methods. We evaluated relative standard error (RSE) and catch of stock-length individuals for NASM Largemouth Bass Micropterus salmoides electrofishing surveys and NASM crappie (Pomoxis spp.) fyke net surveys in Ohio reservoirs 2003–2017. We then used resampling methods to estimates sample sizes required to meet two sampling objectives: (1) for CPUE, achieve an RSE = 25; and, (2) collect at least 100 stock-length fish. We found that Largemouth Bass and crappie surveys generally met sampling objectives. Resample analysis showed that the median number of samples required to meet objectives for Largemouth Bass surveys was 12 or fewer and the median for crappie surveys was 20 or fewer. Our results support literature that shows NASM electrofishing can be used to obtain precise Largemouth Bass samples that meet catch objectives with a reasonable sample size. Our crappie survey results contrasted literature that shows NASM fyke net methods required prohibitively large sample sizes to meet precision and catch objectives. This analysis advances our understanding of sample size requirements for standard methods and highlights the importance of estimating sample size when designing standard surveys. Furthermore, we propose a standard resampling method for estimating sample size requirements.
AUTHORS: Andrew Bueltmann, Sandra Clark-Kolaks – Indiana Department of Natural Resources
ABSTRACT: Two entrapment gears, the Indiana Standard trap net (INS) and the Small Lake Michigan trap net (LM), were compared to evaluate which was more efficient and more cost effective for collecting Crappie. Gears were deployed randomly at four total lakes, one in 2017 and three in 2018. Efficiency was measured by effort needed to collect a similar sample size between gears along with time required to run both nets. Further, cost effectiveness was measured by the individual cost of both nets and the number of cheap nets which could be purchased for the more expensive net. Specifically, a single LM costs ~$4,500 and a single INS costs ~$500; therefore, nine INS could be purchased for one LM. Cost effectiveness was then calculated as the ratio of estimated catch:estimated labor time to run the necessary number of nets so that individual costs were equivalent (i.e., one LM to nine INS). The larger the ratio, the more cost effective the gear type. All lake data were pooled for analysis and indicate that size distribution between nets does not differ and mean overnight catch rates were nearly triple the amount higher for LM (14.8) than INS (5.6). Further, labor time required to achieve equivalent catch rates were as follows: one LM net (~9.8 to 60.4 mins to run) to three INS nets (~10.5 to 58.8 mins to run). Although mean overnight catch rate was higher for LM, cost effectiveness indicates little to no difference between the gears with INS (0.7) being slightly more cost effective than LM (0.5).
AUTHORS: Nick Kramer, Kansas Department of Wildlife, Parks, and Tourism
ABSTRACT: Gill nets are one of the most popular gears implemented to assess fish populations in North America. Ease of construction and low maintenance has led to their success and widespread implementation in the field of fisheries management. The characteristics of a gill net, along with the size and shape of the fish affect how capture occurs (i.e., wedging, gilling, tangling, or a combination). Many studies have been completed on selectivity of various sizes of mesh. Despite the importance of mesh size, the shape of the mesh can also be altered by modifying the hanging ratio which in turn will affect the catchability of fishes with differing body shapes. Additional studies have demonstrated the effectiveness of hobbling or tying down gill nets. This creates more of a “baggy” net which studies have shown to capture a wider size range of fish and may increase catches of species that could easily become tangled due to external protrusions (e.g., Channel Catfish or Paddlefish). In recent years, Kansas Department of Wildlife, Parks, and Tourism biologists have become interested in managing Blue and Flathead Catfish and have placed an increased priority on sampling these species; however, the biologists currently have little insight into fully representative population parameters due to standardized sampling gear that does not capture larger individuals. Thus, the objective of this study is to evaluate the effectiveness of various gill net designs to sample fish populations in Kansas impoundments with special consideration given to species of interest for biologists (e.g., Blue Catfish, Flathead Catfish). Year one of this study found differences in catch rates for some commonly assessed species. These differences were further examined in year two of the study by expanding the sample size; in both number of sets and number of reservoirs.
AUTHORS: Nicholas B. Kludt, South Dakota State University; Mark J. Fincel, South Dakota Game, Fish & Parks; Brian D.S. Graeb, South Dakota State University
ABSTRACT: Rainbow Smelt Osmerus mordax and Cisco Coregonus artedi are the primary coldwater forage species in Lake Oahe, South Dakota. Understanding the dynamics of these species is an important aspect of Walleye Sander vitreus and Chinook Salmon Oncorhynchus tshawytscha management. As these coldwater species are pelagic and heterogeneously distributed throughout the stratified reservoir zone, they have been historically surveyed using hydroacoustics. Hydroacoustics offers the ability to efficiently survey large areas, but can be time consuming. We compared the traditional cross-sectional transects (2.5 ± 0.8 km) with an abbreviated longitudinal transect (0.5 ± 0.0 km) survey, using a paired design replicated over three months and two years (n=97). We then analyzed the observed target densities of Rainbow Smelt and Lake Herring using a mean square error (MSE) approach. Observed densities were highly correlated for both Rainbow Smelt (r = 0.91) and Cisco (r = 0.94). Decomposing MSE revealed random error components of 67.3% and 99.7% of Rainbow Smelt and Cisco, respectively, indicating no systemic differences between the paired estimates. In either case, estimates were statistically comparable to a 1:1 line with a zero intercept, indicating high observational agreement. These results show no discernible difference between survey designs. While travel time between sites remains constant, the difference between longitudinal (6 min) and cross sectional (30 min) transect scanning times equates to an 80% time savings (1 hr, 42 mins vs. 8 hr, 38 mins). We therefore recommend the adoption of the longitudinal design for future standardized sampling of Lake Oahe coldwater stocks.
AUTHORS: Sabina Berry, Jim Lamer – Western Illinois University; Jason DeBoer, Andrya Whitten – Illinois Natural History Survey; Rob Colombo, Cassi Carpenter – Eastern Illinois University; Neil Rude, Greg Whitledge – Southern Illinois University Carbondale; Ben Lubinski, Jerrod Parker – Illinois Natural History Survey
ABSTRACT: Channel catfish (Ictalurus punctatus) and Freshwater drum (Aplodinotus grunniens) are two prominent North American sportfishes occupying a similar ecological niche in many river systems. Comparison of historically validated ageing structures and length frequency data can reveal dynamics of fish populations, including their recruitment, mortality, and individual growth patterns. In addition, tracking years of strong and weak growth through biochronological inference can increase understanding of the biotic and abiotic factors affecting individual reaches and rivers. This collaborative project covers reaches of six major rivers spanning Illinois, including the Wabash, Ohio, Illinois, Kankakee, Iroquois, Pools 16, 19, 20, 21, and 25 of the upper Mississippi River, as well as a small section of the lower Mississippi River. All fish were caught in 2017 and 2018 using DC electrofishing gear as part of a long term survey submitted annually to the Illinois Department of Natural Resources. Preliminary results from 2017 revealed weak year classes in all reaches for drum from 2010 to 2014, but stronger classes in the following years. Catfish showed weak years before 2011 and after 2014, but stronger years in between. Drum had faster growth rates in the Ohio and Mississippi reaches and slower growth in the Illinois and Wabash, whereas the catfish initially had faster growth rates only in the Ohio River. Mortality rates were highest for drum in the upper Mississippi River in pools 16 & 19, but lowest in the Ohio River. Catfish mortality rates were low throughout all reaches. Incorporating chronology factors as well as the data collected in 2018 may reveal additional trends and the larger dataset will allow us to further compare pools and reaches within each river. Understanding population dynamics and growth chronology of two common predatory fish spanning Illinois waterways is important for creating potential management strategies and determining their initial necessity.
