Christopher Vandergoot - Academia.edu (original) (raw)

Papers by Christopher Vandergoot

Lake Erie’s walleye Sander vitreus population has undergone dramatic fluctuations over the past c... more Lake Erie’s walleye Sander vitreus population has undergone dramatic fluctuations over the past century for a variety of reasons, including overexploitation and ever changing characteristics of the lake’s biological, physical, and chemical environment. Despite these fluctuations, walleye have proven to be resilient and continue to support economically important recreational and commercial walleye fisheries. Several papers have described the changes in abundance, harvest, and management up until the mid-1980s. This paper is intended to provide an overview of changes to the walleye population and fishery in Lake Erie since that time and discuss implications for the future. For the past two decades, the walleye population has oscillated from a historic high, followed by a steady decline, to a recent peak in abundance. Similarly, the forage base has changed from a community dominated by soft-rayed and clupeid species (e.g., emerald shiners Notropis atherinoides and gizzard shad Dorosoma...

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Fishery-independent (FI) surveys provide critical information used for the sustainable management... more Fishery-independent (FI) surveys provide critical information used for the sustainable management and conservation of fish populations. Because fisheries management often requires the effects of management actions to be evaluated and detected within a relatively short time frame, it is important that research be directed toward FI survey evaluation, especially with respect to the ability to detect temporal trends. Using annual FI gill-net survey data for Lake Erie walleyes Sander vitreus collected from 1978 to 2006 as a case study, our goals were to (1) highlight the usefulness of hierarchical models for estimating spatial and temporal sources of variation in catch per effort (CPE); (2) demonstrate how the resulting variance estimates can be used to examine the statistical power to detect temporal trends in CPE in relation to sample size, duration of sampling, and decisions regarding what data are most appropriate for analysis; and (3) discuss recommendations for evaluating FI surveys and analyzing the resulting data to support fisheries management. This case study illustrated that the statistical power to detect temporal trends was low over relatively short sampling periods (e.g., 5-10 years) unless the annual decline in CPE reached 10-20%. For example, if 50 sites were sampled each year, a 10% annual decline in CPE would not be detected with more than 0.80 power until 15 years of sampling, and a 5% annual decline would not be detected with more than 0.8 power for approximately 22 years. Because the evaluation of FI surveys is essential for ensuring that trends in fish populations can be detected over management-relevant time periods, we suggest using a metaanalysis-type approach across systems to quantify sources of spatial and temporal variation. This approach can be used to evaluate and identify sampling designs that increase the ability of managers to make inferences about trends in fish stocks.

ABSTRACT Walleye is an important commercial and recreational fish in Saginaw Bay, Lake Huron. Wal... more ABSTRACT Walleye is an important commercial and recreational fish in Saginaw Bay, Lake Huron. Walleye spawning in the Tittabawassee River, tributary to Saginaw Bay, represent the largest spawning stock of walleye in Lake Huron. Understanding walleye movement and thermal ecology will help better define the scope and timing of movement of segments of this stock. This study will determine the association of sex, size and age on walleye movement and thermal habitat after they spawn. The Great Lakes Acoustic Telemetry Observing System is being used to track 200 walleye from the Tittabawassee River. Walleye were tagged between March 28 and April 4 2011 through coelomic implantation of acoustic transmitters equipped with temperature loggers. Specific objectives are to determine the timing of outmigration from both the river and Saginaw Bay relative to fish sex, age and size. In addition, data from temperature loggers recovered from tagged fish will enable us to evaluate the thermal experience of fish relative to sex. This presentation will provide information about the first year of outmigration telemetry data as well as an overview of findings related to thermal biology of walleye.

Ecology of Freshwater Fish, 2016

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Journal of Thermal Biology, 2015

The purpose of this study was to characterize thermal patterns and generate occupancy models for ... more The purpose of this study was to characterize thermal patterns and generate occupancy models for adult walleye from lakes Erie and Huron with internally implanted biologgers coupled with a telemetry study to assess the effects of sex, fish size, diel periods, and lake. Sex, size, and diel periods had no effect on thermal occupancy of adult walleye in either lake. Thermal occupancy differed between lakes and seasons. Walleye from Lake Erie generally experienced higher temperatures throughout the spring and summer months than did walleye in Lake Huron, due to limnological differences between the lakes. Tagged walleye that remained in Saginaw Bay, Lake Huron (i.e., adjacent to the release location), as opposed to those migrating to the main basin of Lake Huron, experienced higher temperatures, and thus accumulated more thermal units (the amount of temperature units amassed over time) throughout the year. Walleye that migrated toward the southern end of Lake Huron occupied higher temperatures than those that moved toward the north. Consequently, walleye that emigrated from Saginaw Bay experienced thermal environments that were more favorable for growth as they spent more time within their thermal optimas than those that remained in Saginaw Bay. Results presented in this paper provide information on the thermal experience of wild fish in a large lake, and could be used to refine sex- and lake-specific bioenergetics models of walleye in the Great Lakes to enable the testing of ecological hypotheses.

Walleye support a multi-billion dollar fishery on the Great Lakes. A large-scale acoustic telemet... more Walleye support a multi-billion dollar fishery on the Great Lakes. A large-scale acoustic telemetry study was conducted in lakes Erie and Huron to better understand movement patterns within and between lakes and provide critical information to support management. Detection data were used to identify environmental and biological characteristics associated with the timing and extent of walleye movement from riverine spawning grounds into the lakes and back again. Spawning walleye in the Tittabawassee River, Michigan and the Maumee River, Ohio were implanted with acoustic transmitters during 2011-2012 and their movements during subsequent spawning seasons were monitored. Zero-inflated Poisson models were used to test effects of environmental conditions and biological characteristics on pre- and post-spawning walleye movements. A model including sex, Julian day, water temperature, and river discharge accounted for the greatest percentage of variation in fish movements into rivers during...

North American Journal of Fisheries Management, 2015

Genetic stock identification analyses were conducted to determine spawning population contributio... more Genetic stock identification analyses were conducted to determine spawning population contributions to the recreational fishery for Walleyes Sander vitreus in Saginaw Bay, Lake Huron. Two spawning population groups were considered: (1) the Tittabawassee River, which has been identified as the largest source of spawning Walleyes for Saginaw Bay; and (2) an aggregate of six spawning populations from Lake Erie and Lake St. Clair that were found to be genetically similar. Overall, the Lake Erie and Lake St. Clair spawning populations were estimated to comprise approximately 26% of the Walleye recreational harvest in Saginaw Bay during 2008-2009. Contribution levels were similar for the 2 years in which genetic samples were collected. Contributions from the Lake Erie and Lake St. Clair spawning populations to the harvest of age-5 and older Walleyes were greater during summer (31.8%; SE D 6.2%) than during late winter and spring (6.0%; SE D 3.7%). Conversely, contributions from the Lake Erie and Lake St. Clair spawning populations to the harvest of age-3 and age-4 fish were fairly similar between seasons (late winter and spring: 31.2%, SE D 6.7%; summer: 41.7%, SE D 5.6%), suggesting that younger Walleyes migrate earlier or reside in Saginaw Bay for extended periods. Our finding that one-quarter of the Saginaw Bay recreational harvest of Walleyes comprises fish from Lake Erie and Lake St. Clair has important management implications, as policies for one lake may have bearing on the other lake-one of the challenges

Fisheries Research, 2015

We used stochastic simulations to evaluate accuracy and precision of parameter estimates from spa... more We used stochastic simulations to evaluate accuracy and precision of parameter estimates from spatial tag-recovery models under different combinations of high-and low-reward tagging levels, allocations of tags to different age groups, and patterns in age-specific natural mortalities. Our evaluations were based on Lake Erie walleye (Sander vitreus), which exhibit complex spatial structuring and support economically important recreational and commercial fisheries. In conducting our evaluations, we assumed inter-regional movements of tagged individuals could be treated as fixed (i.e., known) values. Accuracy and precision of parameter estimates generally stabilized at the mid-range tagging levels that were evaluated, suggesting limited gains would result from tagging more fish. Tag-allocation designs did not have large influences on accuracies of fishing mortalities, selectivities, and reporting rates, but accuracies of natural mortality estimates were sensitive to different designs. A skewed tag-allocation design most often had the best level of accuracy for age-5 and older natural mortalities, whereas proportional and balanced designs most often had the best level of accuracy for age-2 and 3 and age-4 natural mortalities, respectively. Results were far from being consistent, however, with other allocation designs sometimes exhibiting better performance under different factor-level combinations. These same tagallocation designs resulted in the best precision for natural mortalities for these same age groups and in this regard results were consistent (i.e., did not vary by factor-level combinations). Our simulations help to understand how accuracy and precision of estimates from spatial tag-recovery models can vary with different design features of tagging studies and should provide beneficial insight for designing tagging studies for spatially structured fish populations.

ABSTRACT Egg size and egg size variability can have important implications for larval fish succes... more ABSTRACT Egg size and egg size variability can have important implications for larval fish success, and may vary intraspecifically through adaptive and plastic mechanisms. While many studies have documented the influences of maternal effects and environmental conditions on egg size variation within populations, few have investigated the impacts of these processes on egg size variation within individuals. Some populations may express more within-individual variation than others because they experience greater environmental unpredictability. Should intra-individual egg size variation be related to maternal traits, it could have important management implications. We evaluated differences in intra-individual egg size variability among several populations of walleye (Sander vitreus) from 2007-2012. There was no relationship between within-female egg size variability and maternal age or total length. Within years, within-individual egg size variation differed significantly among populations, which may reflect different environmental conditions experienced by each population. Year to year, levels of variation in some populations were relatively consistent, while others varied significantly. Populations with low intra-individual variability may experience relatively homogenous environments each year. In contrast, egg size in highly variable populations may be a phenotypically plastic trait. Alternatively, females may produce eggs of a diversity of sizes to maximize their reproductive fitness in an unpredictable environment.

ABSTRACT Suitable walleye habitat in Lake Erie is currently defined for area-based fishery quota ... more ABSTRACT Suitable walleye habitat in Lake Erie is currently defined for area-based fishery quota allocation as depths <13 m. A recent model based upon gillnet data shows that temperature, water clarity, and dissolved oxygen also explain significant variability in walleye distribution, prompting resource managers to consider alternative habitat metrics. We addressed limitations of the gillnet habitat model via acoustic telemetry of walleye with receiver transects deployed along depth gradients in the central basin of Lake Erie. During the 2013 season, we logged 23,485 detections from 88 different fish on 18 receivers. Diel patterns of detections revealed variations in movement that can better inform the gill net model of habitat use. Further, proportions of detections at receiver depths >13m showed a higher than expected utilization of deeper offshore habitats. Dissolved oxygen loggers placed at a subset of receiver locations are allowing us to examine the influence of hypoxic episodes on walleye movements and basin-wide hydroacoustic surveys are providing spatially matched estimates of forage fish abundance as another explanatory variable. This work improves our understanding of walleye habitat use as it relates to spatial management of the most valuable fishery in the Great Lakes.

The Saginaw Bay of Lake Huron supports a popular and economically important recreational walleye ... more The Saginaw Bay of Lake Huron supports a popular and economically important recreational walleye fishery. In the Great Lakes, walleye are thought to undertake extensive within- and between-lake movements. Historically, these movements have not received much research attention, owing to the difficulties in tracking fish at large spatial scales. The advent of new biotelemetry technologies and the implementation of the Great Lakes Acoustic Telemetry Observing System has allowed us to begin understanding the extent and frequency of walleye movements throughout Saginaw Bay and greater Lake Huron. We implanted acoustic transmitters in 200 spawning condition walleye (50:50 males:females) collected by electrofishing in the Tittabawassee River (tributary to Saginaw Bay) during March 28- April 4, 2011. Initial inspection of acoustic recapture data suggest that walleye move widely throughout U.S. waters of both northern and southern Lake Huron. Although the majority of fish moved out of the Ti...

Transactions of the American Fisheries Society, 2014

Although the Lake Erie population of Walleyes Sander vitreus exhibits complex spatial structuring... more Although the Lake Erie population of Walleyes Sander vitreus exhibits complex spatial structuring, the extent to which population demographics also vary spatially is unknown. Using a spatial tag recovery model, we estimated region-and age-specific mortalities and regional movement probabilities by using recoveries from a jaw tagging study initiated in 1990. The best-performing model based on a comparison of quasi-likelihood Akaike's information criterion values had age-group-specific movement probabilities, age-and region-specific natural mortalities, and age-group-and region-specific annual fishing mortalities. Commercial fishing mortality varied considerably during the study, while recreational fishing mortality was more static. Natural mortality of age-5 and older Walleyes was lower than that of younger fish in all regions, with values ranging from 0.30 to 0.40 for age-4 and younger fish and from 0.13 to 0.27 for age-5 and older fish. In Lake Erie's western basin, natural mortality of age-4 fish was lower than that of age-3 fish. Sensitivity analyses indicated that some natural mortality estimates were sensitive to (1) prior probability distributions assigned to mortality components and (2) assumed movement probabilities in regions where no tagging was conducted. The decline in natural mortality with age in Lake Erie's western basin matches what has been found for other populations, suggesting that such patterns are perhaps common in exploited Walleye populations. Movement probabilities in the western basin were greater than those in the combined central and eastern basins. The mortality rates and movement probabilities estimated in this study should assist in the parameterization and scaling of a spatially explicit Lake Erie Walleye assessment model, the development of which has been recommended for the lake's quota management system. Our study is one of the first to apply a spatial tag recovery model to a freshwater fish population for estimating mortality components. We encourage wider use of this method to improve the understanding of how mortality components and movements vary regionally within freshwater systems.

North American Journal of Fisheries Management, 2005

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North American Journal of Fisheries Management, 2008

Yellow perch Perca flavescens support economically important recreational and commercial fisherie... more Yellow perch Perca flavescens support economically important recreational and commercial fisheries in Lake Erie and are intensively managed. Age estimation represents an integral component in the management of Lake Erie yellow perch stocks, as age-structured population models are used to set safe harvest levels on an annual basis. We compared the precision associated with yellow perch (N ¼ 251) age estimates from scales, sagittal otoliths, and anal spine sections and evaluated the time required to process and estimate age from each structure. Three readers of varying experience estimated ages. The precision (mean coefficient of variation) of estimates among readers was 1% for sagittal otoliths, 5-6% for anal spines, and 11-13% for scales. Agreement rates among readers were 94-95% for otoliths, 71-76% for anal spines, and 45-50% for scales. Systematic age estimation differences were evident among scale and anal spine readers; less-experienced readers tended to underestimate ages of yellow perch older than age 4 relative to estimates made by an experienced reader. Mean scale age tended to underestimate ages of age-6 and older fish relative to otolith ages estimated by an experienced reader. Total annual mortality estimates based on scale ages were 20% higher than those based on otolith ages; mortality estimates based on anal spine ages were 4% higher than those based on otolith ages. Otoliths required more removal and preparation time than scales and anal spines, but age estimation time was substantially lower for otoliths than for the other two structures. We suggest the use of otoliths or anal spines for age estimation in yellow perch (regardless of length) from Lake Erie and other systems where precise age estimates are necessary, because age estimation errors resulting from the use of scales could generate incorrect management decisions.

North American Journal of Fisheries Management, 2009

North American Journal of Fisheries Management, 2000

North American Journal of Fisheries Management, 2003

... 10. Hackney, PA and Holbrook, JA II. 1978. ... University. The authors thank Mike Smith, Paul... more ... 10. Hackney, PA and Holbrook, JA II. 1978. ... University. The authors thank Mike Smith, Paul Horner, Lyle Mason, Tim Churchill, Mark Thurman, and Tom Hampton for assistance in marking and collecting walleyes throughout this study. ...

North American Journal of Fisheries Management, 2011