Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Early life survival is critical to successful replenishment of fish populations, and hypotheses developed under the Growth‐Survival Paradigm (GSP) have guided investigations of controlling processes. The GSP postulates that recruitment... more
Early life survival is critical to successful replenishment of fish populations, and hypotheses developed under the Growth‐Survival Paradigm (GSP) have guided investigations of controlling processes. The GSP postulates that recruitment depends on growth and mortality rates during early life stages, as well as their duration, after which the mortality declines substantially. The GSP predicts a shift in the frequency distribution of growth histories with age towards faster growth rates relative to the initial population because slow‐growing individuals are subject to high mortality (via starvation and predation). However, mortality data compiled from 387 cases published in 153 studies (1971–2022) showed that the GSP was only supported in 56% of cases. Selection against slow growth occurred in two‐thirds of field studies, leaving a non‐negligible fraction of cases showing either an absence of or inverse growth‐selective survival, suggesting the growth‐survival relationship is more complex than currently considered within the GSP framework. Stochastic simulations allowed us to assess the influence of key intrinsic and extrinsic factors on the characteristics of surviving larvae and identify knowledge gaps on the drivers of variability in growth‐selective survival. We suggest caution when interpreting patterns of growth selection because changes in variance and autocorrelation of individual growth rates among cohorts can invalidate fundamental GSP assumptions. We argue that breakthroughs in recruitment research require a comprehensive, population‐specific characterization of the role of predation and intrinsic factors in driving variability in the distribution and autocorrelation of larval growth rates, and of the life stage corresponding to the endpoint of pre‐recruited life.
Research Interests:
Research Interests:
Research Interests:
Whether bottom hypoxia has long-lasting consequences for pelagic fish populations remains speculative for most ecosystems. We explored hypoxia’s influence on two pelagic zooplanktivores in Lake Erie that have different thermal... more
Whether bottom hypoxia has long-lasting consequences for pelagic fish populations remains speculative for most ecosystems. We explored hypoxia’s influence on two pelagic zooplanktivores in Lake Erie that have different thermal preferences: cold-water rainbow smelt (Osmerus mordax) and warm-water emerald shiners (Notropis atherinoides). To assess acute effects, we combined predictive bioenergetics-based modeling with field collections made across the hypoxic season in central Lake Erie during 2005 and 2007. To assess chronic effects, we related fishery-independent and fishery-dependent catches with hypoxia severity and top predator (walleye, Sander vitreus) abundance during 1986–2014. As our modeling predicted, hypoxia altered rainbow smelt movement and distributions, leading to avoidance of cold, hypoxic bottom waters. In response, diets shifted from benthic to pelagic organisms, and consumption and energetic condition declined. These changes were lacking in emerald shiners. Our long-term analyses showed rainbow smelt abundance and hypoxia to be negatively related and suggested that hypoxia avoidance increases susceptibility to commercial fishing and walleye predation. Collectively, our findings indicate that hypoxia can negatively affect pelagic fish populations over the long term, especially those requiring cold water.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Abstract. Chemical cues are frequently a key source of information to aquatic organisms. Both predators (kairomones digestive metabolites) and prey (alarm and damage-released cues) may generate chemical cues during their interactions, and... more
Abstract. Chemical cues are frequently a key source of information to aquatic organisms. Both predators (kairomones digestive metabolites) and prey (alarm and damage-released cues) may generate chemical cues during their interactions, and different cue types can have different informational values. How predators and prey use the information from chemical cues to make spatial movement decisions influences both their direct interaction rates and their interactions with other species. We measured the spatial response of predatory larval dragonflies (Anax junius) and predator-naïve green frog (Lithobates clamitans) tadpoles exposed to several types of chemical cues using experimental mesocosms. We found tadpoles only responded with spatial avoidance when exposed to both Anax kairomones and conspecific alarm cues together, whereas Anax did not exhibit consistent spatial responses to any cue type. Our results suggest tadpole prey selectively respond to environmental information from chemical cues (possibly to minimize costly antipredator behavior due to responding to insufficient information or reflecting a need for associative learning). They also show predatory dragonflies may use nonchemical information to make space use decisions (possibly due to inability to detect the same chemical cues as tadpoles).
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Abstract The spermatozoa glycocalyx is a dynamic coating of extracellular glycoproteins known to facilitate the acrosome reaction and fertilization in mammals. Most fish sperm, however, contain no acrosome and are subjected to different... more
Abstract The spermatozoa glycocalyx is a dynamic coating of extracellular glycoproteins known to facilitate the acrosome reaction and fertilization in mammals. Most fish sperm, however, contain no acrosome and are subjected to different stimuli (e.g., osmotic shock in the external environment) prior to fertilization. At present, our understanding of the composition and spatial distribution of sugar moieties and the functional role of the glycocalyx in fish sperm remains incomplete. Moreover, the influence of assisted reproduction techniques (e.g., testicular harvest and cryopreservation) commonly used in aquaculture settings on this structure in fish sperm is unknown. Herein, we describe and compare the composition and characteristics of the glycocalyx among sperm types (stripped, testicular, and cryopreserved) and between activation statuses (inactive vs. activated) using sauger (Sander canadensis) as a model. We also investigated the importance of certain moieties (e.g., N-acetyl-glucosamine [GlcNAc]) to fertilization. Staining distributions, fluorescent intensity, and proportion of cells exhibiting high fluorescence were measured for each treatment using fluorescent microscopy and flow cytometry, respectively. Three lectins, specific to certain glycocalyx sugar moieties (wheat germ agglutinin, WGA [GlcNAc]; concanavalin A, ConA [α-mannose]; and peanut agglutinin, PNA [β-galactose]) were used to monitor these variables in fish sperm. The sauger glycocalyx contained GlcNAc and α-mannose but lacked β-galactose moieties. Testicular sperm exhibited fewer cells (20–40% fewer) with high GlcNAc and α-mannose content than other sperm types. Additionally, the proportion of highly fluorescent cells in testicular sperm were positively correlated with motility (r = 0.80–0.95), suggesting the glycocalyx is affected by post-testicular maturation. Motility activation via hypo-osmotic shock caused a redistribution of GlcNAc to the apical region of the head of 40–50% of stripped and testicular sperm, respectively. Cryopreserved sperm showed significantly reduced apical staining following activation (
Research Interests:
Research Interests:
Research Interests:
Early‐life conditions can have long‐lasting effects (experiential legacies) on an individual's performance. Experiential legacies are an important source of variation among mature individuals because responses to early‐life... more
Early‐life conditions can have long‐lasting effects (experiential legacies) on an individual's performance. Experiential legacies are an important source of variation among mature individuals because responses to early‐life environments vary widely. Yet, the factors influencing the magnitudes and directions of phenotypic responses to experiential legacies are poorly understood, hindering our ability to predict adult phenotypes and population‐level consequences of environmental stressors. To better understand these issues, we examined how experiential legacies varied with the type of phenotypic response (e.g., reproduction, longevity), characteristics of the individual, and characteristics of the stressful conditions imposed. We conducted a meta‐analytic review (nspecies = 65, nstudies = 81), examining experiential legacies of early‐life nutritional restriction. We found generally consistent negative or neutral impacts of early nutritional stress on later‐life phenotypes, indicat...
Research Interests:
Research Interests:
Research Interests:
Abstract The Great Lakes Fishery Commission sponsored a 2-day workshop that sought to enhance the ability of Great Lakes agencies to understand, predict, and ideally manage fisheries production in the face of changes in natural and... more
Abstract The Great Lakes Fishery Commission sponsored a 2-day workshop that sought to enhance the ability of Great Lakes agencies to understand, predict, and ideally manage fisheries production in the face of changes in natural and anthropogenic forcings (e.g., climate, invasive species, and nutrients). The workshop brought together 18 marine and freshwater researchers with collective expertise in aquatic ecology, physical oceanography, limnology, climate modeling, and ecosystem modeling, and two individuals with fisheries management expertise. We report on the outcome of a writing exercise undertaken as part of this workshop that challenged each participant to identify three needs, which if addressed, could most improve the ability of Great Lakes agencies to manage their fisheries in the face of ecosystem change. Participant responses fell into two categories. The first identified gaps in ecological understanding, including how physical and biological processes can regulate early life growth and survival, how life-history strategies vary across species and within populations, and how anthropogenic stressors (e.g., nutrient runoff, climate change) can interact to influence fish populations. The second category pointed to the need for improved approaches to research (e.g., meta-analytic, comparative, spatial translation) and management (e.g., mechanistic management models, consideration of multi-stock management), and also identified the need for improved predictive models of the physical environment and associated ecosystem monitoring programs. While some progress has been made toward addressing these needs, we believe that a continued focus will be necessary to enable optimal fisheries management responses to forthcoming ecosystem change.
Research Interests: Environmental Engineering, Geography, Climate Change, Fisheries Science, Fisheries Management, and 9 moreGreat Lakes, Ecosystem management, Ecosystem Approach, Environmental Resource Management, Ecosystem based management, Fishery, Ecosystem, ENVIRONMENTAL SCIENCE AND MANAGEMENT, and ecosystem model
Research Interests:
A primary goal of fisheries management is to maximize angler satisfaction (e.g., by catching more and bigger fish), while maintaining sustainable populations. In addition to environmental and ecological factors, angler choices may... more
A primary goal of fisheries management is to maximize angler satisfaction (e.g., by catching more and bigger fish), while maintaining sustainable populations. In addition to environmental and ecological factors, angler choices may influence recreational catches. Using interviews (92,838) from Walleye Sander vitreus anglers in Lake Erie during 1989–2017, we identified how angler behavior influences catch outcomes. Angler behaviors were associated with changes in catch rate and the length of harvested fish. For example, trolling resulted in a 50% increase in median catch and a 24‐mm increase in length, relative to casting. Other behaviors led to tradeoffs between catch rate and size, such as the time of year anglers fished. We identified behaviors that maximize fishing success with respect to anglers’ desired catch outcomes. Our results can help increase angler satisfaction by providing realistic catch expectations, given the environmental and fishery conditions, while improving recreational catch outcomes through more informed angler decision making.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
While recent research has shed insight into how bottom hypoxia affects pelagic food webs in coastal marine ecosystems and natural lakes, its effects on man-made lake (reservoir) food webs remains more incomplete. To address this gap, we... more
While recent research has shed insight into how bottom hypoxia affects pelagic food webs in coastal marine ecosystems and natural lakes, its effects on man-made lake (reservoir) food webs remains more incomplete. To address this gap, we conducted a study in two midwestern USA reservoirs to examine how the spatial overlap and vertical distributions of dominant zooplanktivores (i.e., pelagic fish, bentho-pelagic Chaoborus spp.) and their prey vary between periods of normoxia and hypoxia. Surprisingly, we found high levels of spatial overlap between zooplankton and both intermediate consumers (pelagic fish and Chaoborus) during both normoxia and hypoxia, though the extent of spatial overlap was higher during hypoxia at night relative to day. As expected, pelagic fish and zooplankton avoided hypoxic waters, and Chaoborus moved from hypoxic waters during the day to the well-oxygenated surface waters at night. Using our findings, we discuss the potential influence of bottom hypoxia and Chaoborus on the function and structure of north-temperate reservoir food webs.
Research Interests:
Research Interests:
Although previous research has identified ways in which environmental conditions influence population processes in many ecosystems, these relationships often weaken or break down with the inclusion of additional years of data, for reasons... more
Although previous research has identified ways in which environmental conditions influence population processes in many ecosystems, these relationships often weaken or break down with the inclusion of additional years of data, for reasons that remain unclear. To better understand if and how the relationships between historically important environmental drivers of yellow perch (Perca flavescens) recruitment varied during 1969–2018 in two Lake Erie basins characterised by contrasting productivity, we used dynamic linear modelling, which allows for nonstationary relationships between predictor and response variables to be quantified. Our analyses revealed that abiotic conditions during egg and larval development (i.e. winter temperature, springtime river inflows, and thermal conditions) were important in the productive west basin, whereas a combination of abiotic (i.e. winter temperature and river inflows) and biotic (i.e. small‐bodied and large‐bodied predators) conditions were import...
Research Interests:
Understanding environmental driver-response relationships is critical to the implementation of effective ecosystem-based management. Ecosystems are often influenced by multiple drivers that operate on different timescales and may be... more
Understanding environmental driver-response relationships is critical to the implementation of effective ecosystem-based management. Ecosystems are often influenced by multiple drivers that operate on different timescales and may be nonstationary. In turn, contrasting views of ecosystem state and structure could arise depending on the temporal perspective of analysis. Further, assessment of multiple ecosystem components (e.g., biological indicators) may serve to identify different key drivers and connections. To explore how the timescale of analysis and data richness can influence the identification of driver-response relationships within a large, dynamic ecosystem, this study analyzed long-term (1969-2018) data from Lake Erie (USA-Canada). Data were compiled on multiple biological, physical, chemical, and socioeconomic components of the ecosystem to quantify trends and identify potential key drivers during multiple time intervals (20 to 50 years duration), using zooplankton, bird, and fish community metrics as indicators of ecosystem change. Concurrent temporal shifts of many variables occurred during the 1980s, but asynchronous dynamics were evident among indicator taxa. The strengths and rank orders of predictive drivers shifted among intervals and were sometimes taxon-specific. Drivers related to nutrient loading and lake trophic status were consistently strong predictors of temporal patterns for all indicators; however, within the longer intervals, measures of agricultural land use were the strongest predictors, whereas within shorter intervals, the stronger predictors were measures of tributary or in-lake nutrient concentrations. Physical drivers also tended to increase in predictive ability within shorter intervals. The results highlight how the time interval examined can filter influences of lower-frequency, slower drivers and higher-frequency, faster drivers. Understanding ecosystem change in support of ecosystem-based management requires consideration of both the temporal perspective of analysis and the chosen indicators, as both can influence which drivers are identified as most predictive of ecosystem trends at that timescale.
Research Interests:
Research Interests:
Species‐specific target strength (TS)‐to‐length (L) and TS‐to‐weight (W) equations can reduce bias in biomass estimates from hydroacoustic surveys, yet these equations do not exist for most fishes. Equations specific to the Gizzard Shad... more
Species‐specific target strength (TS)‐to‐length (L) and TS‐to‐weight (W) equations can reduce bias in biomass estimates from hydroacoustic surveys, yet these equations do not exist for most fishes. Equations specific to the Gizzard Shad Dorosoma cepedianum, a wide‐ranging and often highly abundant prey fish in North American reservoirs and rivers, do not exist. Herein, we sought to develop TS–L and TS–W equations for Gizzard Shad by insonifying free‐swimming individuals of known sizes (36–209 mm TL) in a net cage at three transducer frequencies (70, 120, and 200 kHz). We derived TS–size relationships using major‐axis regression (MAR) and least‐squares regression (LSR), comparing our resultant TS–L equations to a commonly used multispecies equation (Love 1971). To determine how our Gizzard Shad‐specific equations affected estimates of prey fish biomass, we conducted mobile hydroacoustic surveys in four small, shallow Midwestern reservoirs and then estimated biomass using each equatio...
Research Interests:
Research Interests:
Management agencies commonly stock Channel Catfish Ictalurus punctatus as advanced yearlings instead of fingerlings (age 0) to help reduce potential predation mortality despite uncertainty regarding the degree to which predation limits... more
Management agencies commonly stock Channel Catfish Ictalurus punctatus as advanced yearlings instead of fingerlings (age 0) to help reduce potential predation mortality despite uncertainty regarding the degree to which predation limits fingerling poststocking survival. To better understand whether fingerling survival during the first 7 d after stocking—when predation risk is likely greatest—could benefit from the presence of alternative prey fish, we conducted an experiment in 0.4‐ha ponds (N = 18; 6 ponds/treatment) that measured fingerling (TL range = 56–186 mm) survival in ponds with predators only (adult Largemouth Bass Micropterus salmoides; mean TL = 327 mm; SE = 21), with predators and alternative prey fishes (Bluegill Lepomis macrochirus and Goldfish Carassius auratus), or with neither (i.e., control ponds). Without alternative prey, fingerling Channel Catfish survival 1 week after stocking was significantly (P < 0.01) lower (89%) than in the ponds with alternative prey (...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The Channel Catfish Ictalurus punctatus is a popular sport fish that is routinely stocked into north‐temperate U.S. lakes and reservoirs by natural resource management agencies. We experimentally tested the use of an internal coded wire... more
The Channel Catfish Ictalurus punctatus is a popular sport fish that is routinely stocked into north‐temperate U.S. lakes and reservoirs by natural resource management agencies. We experimentally tested the use of an internal coded wire tag (CWT) as a method for nonlethal batch marking of individuals. The retention of CWTs and their influence on individual growth and mortality remain unexplored for juvenile Channel Catfish. Both attributes were quantified and compared between age‐0 fingerlings and age‐1 yearlings at various time points (i.e., after 1 week, 2 weeks, 1 month, and monthly thereafter) of our 4‐month experiment. For both age‐classes, CWT retention was high (90–100%), with no observed increases in mortality or effects on growth rate. Our findings suggest that CWTs are a reliable, effective means of marking juvenile Channel Catfish. Hence, we recommend their use by management agencies to differentiate between hatchery‐reared and wild‐produced individuals, which can be usef...
Research Interests:
High‐turbidity events (HTEs) are common phenomena in shallow‐water environments that can alter ecological interactions. The relative contributions of river input (external loading) vs. resuspension (internal loading) to the occurrence,... more
High‐turbidity events (HTEs) are common phenomena in shallow‐water environments that can alter ecological interactions. The relative contributions of river input (external loading) vs. resuspension (internal loading) to the occurrence, duration, and influenced areas of HTEs are not fully understood in most systems, owing to the lack of long‐term, source‐specified sediment maps. Using a Finite Volume Community Ocean Model‐based wave‐current forced sediment model, we investigated sediment dynamics in the shallow, river‐dominated Western Lake Erie during ice‐free cycles (April–November) of 2002–2012. Results indicated that wind waves predominated sediment dynamics in the offshore areas, with river discharges causing substantial inshore to offshore gradients. Owing to varying wind waves and river discharges, both the mean and extreme sediment dynamics had distinctive seasonal variations. The basin was turbid during spring and fall, with frequent (> 15%), broad (O [102–103 km2]), and ...