Zachary S. Feiner

• PhD
• Researcher at Wisconsin Department of Natural Resources

Size-selective harvest of fish stocks can lead to maturation at smaller sizes and younger ages, which may depress stock productivity and recovery. Such changes in maturation may be very slow to reverse, even following complete fisheries closures. We evaluated temporal trends in maturation of five Great Lakes stocks of yellow perch (Perca flavescens...

Fisheries are selective, capturing fish based on their body size, behaviour, life stage, or location. Over time, if harvest pressure is strong enough and variation in traits heritable, evolution can occur that affects key aspects of the ecology of fish stocks. Most compelling examples of rapid evolution in response to harvest have come from marine...

Shifting temporal or non-linear relationships between angler behavior and fish population characteristics can mask population declines or produce unexpected regulation outcomes. We tested for hyperstability in seasonal and interannual trends in angler effort, catch, and harvest rates in bluegill (Lepomis macrochirus), black crappie (Pomoxis nigroma...

Fish recruitment is complex and difficult to predict. Data-driven approaches show promise for predicting recruitment and understanding its drivers. We used a random forest model to infer relationships between year-class strength and 17 variables describing potential recruitment drivers across 30+ years of walleye (Sander vitreus) data from Minnesot...

Inland fisheries face increasing threats to their sustainability. Despite speculation that depensation may exacerbate the effects of stressors on population resiliency, depensation has not been empirically explored in freshwater fisheries. Declining productivity of walleye (Sander vitreus) populations in northern Wisconsin foreshadows an underlying...

As anthropogenic disturbances rapidly change natural environments, species must respond to new selective pressures shaping rates of reproduction, growth, and mortality. One example is intense fisheries harvest, which can drive the evolution of heavily fished populations toward maturation at smaller sizes and younger ages. Changes in maturation have...

Many walleye populations in the Midwestern United States have declined due to inconsistent or failed natural recruitment, with stocking often failing to rehabilitate natural recruitment or sustain quality fisheries for tribal subsistence and angler harvest opportunity. Numerous factors have been implicated in walleye natural recruitment declines in...

Improvements in angler technology over time have the potential to increase angler success and fish catchability. Recent research testing for the influences of angler technology on fish catch rates have been mixed, with some studies showing a positive influence of technology use and others with no effect. Knowing that angler technology has improved...

Walleye (Sander vitreus), a key opportunistic apex predator in freshwater ecosystems and a cornerstone of regional fisheries, are experiencing population decline due to poor natural recruitment. Maternal effects on egg characteristics, like egg and oil droplet size, can influence egg quality and larval survival. Insights into these traits are essen...

Objective Understanding angler responses to fisheries management actions, such as regulation changes, has important implications for the effectiveness and efficacy of such management strategies. We examined whether vehicle counters could provide a relative index of angler effort, and we present a case study demonstrating use of vehicle counters to...

Climate change is altering the thermal habitats of freshwater fish species. We analyze modeled daily temperature profiles from 12,688 lakes in the US to track changes in thermal habitat of 60 lake fish species from different thermal guilds during 1980-2021. We quantify changes in each species’ preferred days, defined as the number of days per year...

Optimal egg size theory implies that female organisms balance between fecundity and individual offspring investment according to their environment. Past interspecific studies suggest that fishes in large marine systems generally produce smaller eggs than those in small freshwater systems. We tested whether intraspecific egg size variation reflected...

The landscape theory of food web architecture (LTFWA) describes relationships among body size, trophic position, mobility, and energy channels that serve to couple heterogenous habitats, which in turn promotes long‐term system stability. However, empirical tests of the LTFWA are rare and support differs among terrestrial, freshwater, and marine sys...

Rapid technological advancement often receives a mix of criticism and welcome implementation. Fishing technologies, such as sonar, are believed to enable anglers to be more efficient and effective in their angling. There are concerns from anglers and managers of increased catch by technology users. We assessed the relationships between technology u...

Preventative monitoring is an important tool for invasive species management because it allows managers to detect introductions early and take response actions that lead to successful containment or eradication. Since fish are generally attracted to areas with high quality habitat, knowing where these areas are located can be important for ensuring...

Bighead Carp, Hypophthalmichthys nobilis, and Silver Carp, Hypophthalmichthys molitrix, have important negative ecological and economic impacts in areas where they have become established. Therefore, preventing the spread of these species is a primary focus throughout much of the US. In recent years, portions of eastern North and South Dakota have...

Individual and environmental factors may influence gamete characteristics and contributions to recruitment in fishes. We tested for the influence of maternal, abiotic, and biotic factors on egg diameter and quality (i.e., oil droplet diameter) for walleye Sander vitreus in Escanaba Lake, Wisconsin, during 2018-2023 (omitting 2020). Analyses were co...

The phenology of critical biological events in aquatic ecosystems is rapidly shifting due to climate change. Growing variability in phenological cues can increase the likelihood of trophic mismatches (i.e., mismatches in the timing of peak prey and predator abundances), causing recruitment failures in important fisheries. We assessed changes in the...

Individual, sex-specific, and environmental factors may influence gamete characteristics and contributions to recruitment. We examined the influence of maternal, abiotic, and biotic factors on egg size (i.e., diameter) and quality (i.e., oil droplet size) of walleye (Sander vitreus) in Escanaba Lake, Wisconsin, during 2018-2023 (omitting 2020). Ana...

The Fisheries Working Group of WICCI (the Wisconsin Initiative on Climate Change Impacts) is made up of academic, tribal, state, and federal researchers and managers across Wisconsin. We investigate the effects of a changing climate on Wisconsin’s cold, cool, and warmwater fisheries, and seek to identify climate adaptation options for agencies and...

Fish recruitment is influenced by myriad abiotic and biotic factors that vary in space and time. Potential “critical periods” may exist when the presence or absence of optimal environmental conditions determines year class strength; however, critical periods are difficult to identify quantitatively (often being summarized as, e.g., average spring t...

Individual, sex-specific, and environmental factors may influence gamete characteristics and contributions to recruitment in fishes. We tested for the influence of maternal, abiotic, and biotic factors on egg diameter and quality (i.e., oil droplet diameter) for walleye (Sander vitreus) in Escanaba Lake, Wisconsin, during 2018-2023 (omitting 2020)....

Understanding age and growth are important for fisheries science and management; however, age data are not routinely collected for many populations. We propose and test a method of borrowing age–length data across increasingly broader spatiotemporal levels to create a hierarchical age–length key (HALK). We assessed this method by comparing growth a...

Fish stocks generally exhibit high interannual variability in recruitment, and past research has suggested the truncation of a stock’s size- and age-distribution may exacerbate such variability. Individual female fish often differ in reproductive traits like fecundity, offspring size and annual spawn timing. These traits are thought to be related t...

Recruitment depensation describes elevated juvenile mortality with declining adult population size which can prevent or delay stock recovery. Understanding the factors influencing when a population undergoes depensation provides resource agencies with targets for management action. Using estimates of depensation from 28 walleye (Sander vitreus, Per...

Walleye population productivity is influenced by water temperature and water clarity, and available evidence suggests that model-predicted thermal-optical habitat area (TOHA) considered optimal for walleye populations has declined in the upper Midwest. Despite apparent relationships between TOHA and walleye populations, estimation of TOHA relies on...

Project updates on thesis research related to thermal-optical habitat area (TOHA) and walleye populations.

Understanding seasonal differences in species-specific vulnerabilities to recreational angling can be important for informing sustainable fisheries management practices, like fishing seasons or season-specific regulations. However, comparisons of angler catch and harvest rates among seasons with disparate modes of fishing, like open water and ice a...

Recruitment depensation describes elevated juvenile mortality with declining adult population size which can prevent or delay stock recovery. Understanding the factors influencing when a population undergoes depensation provides resource agencies with targets for management action. Using estimates of depensation from 28 walleye (Sander vitreus, Per...

Available evidence suggests that walleye population status is influenced by water temperature and light levels and that the availability of thermal-optical habitat area (TOHA) considered optimal for walleye growth has changed over time. Despite the apparent connection between TOHA and population status, no previous study has empirically assessed wa...

Walleye (Sander vitreus) survival to the fall recruitment stage has notably declined over time within the Ceded Territories of northern Wisconsin with many hypothesized and potentially interactive causes. Failure to recruit can have cascading effects within lake ecosystems, which can be exacerbated by other sources of walleye decline such as produc...

Understanding and predicting recruitment, longstanding goals in fisheries science and ecology, are complicated by variation in the importance of environmental drivers coupled with the dynamic nature of individual ecosystems. Developing an understanding of recruitment from well‐monitored stocks offers an opportunity to overcome these complexities. W...

Declining body size is believed to be a universal response to climate warming and has been documented in numerous studies of marine and anadromous fishes. The Salmonidae are a family of coldwater fishes considered to be among the most sensitive species to climate warming; however, whether the shrinking body size response holds true for freshwater s...

Preventing invasive species establishment is a global conservation priority, yet limited management resources oftentimes restrict sites to target for prevention or monitoring. Risk assessments based on habitat suitability can identify sites most vulnerable to invasion that should be prioritized for preventative actions. Since habitat suitability is...

Walleye Sander vitreus natural recruitment has declined in northern Wisconsin lakes over time. Several factors have been implicated to explain Walleye natural recruitment declines in Wisconsin including climate change, Largemouth Bass Micropterus salmoides interactions, less desirable fish communities, production overharvest, and depensatory effect...

Bayesian inference is a powerful tool that is increasingly being used by ecologists. This is largely due to the flexibility in model specification and improvements in software that makes this tool easier to use. However, with increasing ease of use comes a risk of misuse or abuse. We review four major issues we have identified in the use of Bayesia...

Climate change is leading to shifts in not only the average timing of phenological events, but also their variance and predictability. Increasing phenological variability creates a stochastic environment that is critically understudied, particularly in aquatic ecosystems. We provide a perspective on the possible implications for increasingly unpred...

Lake ecosystems are shifting due to many drivers including climate change and landscape-scale habitat disturbance, diminishing their potential to support some fisheries. Walleye Sander vitreus (Mitchill) populations, which support recreational and tribal fisheries across North America, have declined in some lakes. Climate change, harvest, invasive...

Freshwater recreational fisheries regulations are a vital tool for achieving social and ecological fisheries objectives. However, angler behavior and fish biology may interact to influence regulation efficacy in unexpected ways. We combined models of fish growth and angler behavior to explore how angler behavior interacts with fish life history to...

Decision-makers in inland fisheries management must balance ecologically and socially palatable objectives for ecosystem services within financial or physical constraints. Climate change has transformed the potential range of ecosystem services available. The Resist-Accept-Direct (RAD) framework offers a foundation for responding to climate-induced...

Understanding influences of angler proximity on fisheries resources, the distances anglers are willing to travel, their success rates after they arrive, and seasonal ecological patterns could influence fisheries resiliency, license sales, and management. The Northern Highlands Fishery Research Area near Boulder Junction, Vilas County, WI maintains...

Understanding influences of angler proximity on fisheries resources, in the distances anglers are willing to travel for angling opportunities and their success rates after they arrive, could influence fisheries resiliency and management applications. The Wisconsin Department of Natural Resources, Northern Highland Fishery Research Area (NHFRA), Vil...

Complex life history behaviours like spawning migrations can complicate population assessments. However, predictable aggregation of populations at certain times of year (e.g. at spawning grounds) presents an effective way to sample species that are otherwise spatially widespread. From 2014 to 2019, a mark‐recapture study on Green Bay northern pike...

Understanding influences of human proximity to natural resources, the distances recreationalists are willing to travel, and their success after arrival could influence open-access resource resiliency and management. The Northern Highlands Fishery Research Area near Boulder Junction, Vilas County, WI maintains a compulsory creel census for five rese...

Understanding influences of angler proximity on fisheries resources, the distances anglers are willing to travel, and their success rates after they arrive could influence fisheries resiliency and management. The Northern Highlands Fishery Research Area near Boulder Junction, Vilas County, WI maintains a compulsory creel census for five research la...

Fish natural recruitment is influenced by abiotic and biotic factors. Natural recruitment has declined in northern Wisconsin Walleye Sander vitreus populations over time. Previous research has suggested that White Crappie Pomoxis annularis may negatively influence Walleye recruitment. We used Black Crappie Pomoxis nigromaculatus and age-0 Walleye r...

Climate change is influencing the timing of ecological events (in other words, their phenology) in natural systems globally. In lakes, the timing of important events like ice off, fish spawning, and plankton blooms are not only shifting earlier; they are also becoming much more unpredictable in their phenology from year to year. Such variability ha...

Since the mid‐2000s, recruitment of Walleye Sander vitreus in some northern Wisconsin lakes has declined, potentially because of climate‐induced changes in lake environments. Yellow Perch Perca flavescens is also an ecologically and culturally important fish species in this region, but mechanisms driving Yellow Perch recruitment are unclear because...

Inland recreational fishing, defined as primarily leisure‐driven fishing in freshwaters, is a popular pastime in the USA. State natural resource agencies endeavor to provide high‐quality and sustainable fishing opportunities for anglers. Managers often use creel and other angler survey data to inform state‐ and waterbody‐level management efforts. D...

The ability for individuals to adapt to local food sources likely allows for regional persistence of aquatic populations. In the Laurentian Great Lakes, invasive species and changing physical conditions have vastly altered local and regional food webs, leading to the potential for variation in energy flow up to large predators. To assess the potent...

Size spectra analysis (SSA) is used to detect changes in food webs by simplifying complex community structures through abundance-versus-biomass considerations. We applied SSA to 10 years (2006–2015) of data on Great Lakes organisms ranging in size from picoplankton to macrozooplankton. Summer pelagic size spectra slopes were near the theoretical va...

An understanding of angler catch rate characteristics related to proximity of residence to lakes (local, non-local, non-resident) is important for informing fisheries management. The Northern Highland Fishery Research Area compulsory creel census records zip code data from all anglers fishing Escanaba, Nebish, and Pallette lakes near Boulder Juncti...

Information about species-specific angler catch rates during the open water versus the ice season are limited. We used all available Wisconsin Department of Natural Resources creel survey data during 1990-2020 to test for differences in Black Crappie, Bluegill, Northern Pike, Walleye, and Yellow Perch angler catch rates between open water (May-Octo...

Natural recruitment has declined in northern Wisconsin Walleye populations over time. Several factors have been implicated to explain Walleye natural recruitment declines including climate change, centrarchids, imbalances in fish communities, overexploitation, and cultivation/depensation effects. Anecdotal evidence has suggested that Walleye and Bl...

Depensatory recruitment, wherein recruitment declines with declining stock size, may erode fish population resiliency and prevent the rehabilitation of collapsed stocks. However, depensation has rarely been empirically explored due to the difficulty of characterizing stock-recruitment dynamics at low population sizes and relative paucity of long ti...

Understanding the evolutionary impacts of harvest on fish populations is important for informing fisheries management and conservation and has become a growing research topic over the last decade. However, the dynamics of fish populations are highly complex, and phenotypes can be influenced by many biotic and abiotic factors. Therefore, it is vital...

In Lake Michigan, the unintended introduction of invasive species (e.g., zebra mussel, Dreissena polymorpha; quagga mussel, D. rostriformis bugensis; round goby, Neogobius melanostomus) and reduced nutrient loading has altered nutrient dynamics, system productivity, and community composition over the past two decades. These factors, together with s...

From the development of paleolithic fish hooks, spears, and nets to today’s powerful motors and high‐tech sonar, new fishing technology has usually been accompanied by increases in total effort and catch (Jackson 2001). Thus, angler innovation represents a possible mechanism driving hyperstability in catch rates and lack of self‐regulation in fishe...

Stock reproductive potential informs population dynamics and response to harvest. Indices of body condition, like relative weight (Wr), may indicate individual energetic state and provide a mechanistic link between spawning stock traits and recruitment. We tested for relationships among Wr of three female size classes (381–456, 457–557, and ≥558 mm...

Ecological complexity may improve ecosystem function, stability and adaptability to natural and anthropogenic disturbances. Intraspecific trophic variation can represent a significant component of total community variation and can influence food web structure and function. Thus, understanding how trophic niches are partitioned between intraspecific...

Spatially-correlated abiotic and biotic conditions can potentially induce synchrony in the dynamics of disparate populations or species. However, such potential synchrony among species or populations may be tempered by dynamics operating at finer temporal and spatial scales, as well as species-specific responses to environmental conditions. We exam...

The detrimental impacts of invasive species often occur through deleterious trophic interactions (e.g., competition) with native species. However, the potential for competitive interactions between species may vary among systems, seasons, or throughout species’ ontogeny, requiring a thorough examination of trophic niches to determine whether overla...

In aquatic systems, food web linkages are often assessed using diet contents, stable isotope ratios, and, increasingly, fatty acid composition of organisms. Some correlations between different trophic metrics are assumed to be well-supported; for example, particular stable isotope ratios and fatty acids seem to reflect reliance on benthic or pelagi...

Fish sample sizes and lengths. Sample sizes and mean total lengths (± 1 S.D.) of Lake Michigan fish whose trophic markers were directly compared, grouped by collection location (site) and species (ROG = round goby, STS = spottail shiner, YEP = yellow perch). (PDF)

Fatty acid principal components analysis. Principal component loadings for fatty acids in the Diet-Fatty acid and Stable isotope-Fatty acid data sets. Values in bold italics are greater than |0.2|. (PDF)

Microplastics are present in aquatic ecosystems the world over and may influence the feeding, growth, reproduction, and survival of freshwater and marine biota; however, the extent and magnitude of potential effects of microplastics on aquatic organisms is poorly understood. In the current study, we conducted a meta-analysis of published literature...

Ecologists often focus on summarized composition when assessing complex, multivariate phenotypes such as fatty acids. Increasing complexity in fatty acid composition may offer benefits to individuals that may not be recognized by assessing mean fatty acid identity. We quantified fatty acid identity and complexity in the egg and muscle of spawning f...

Offspring size can strongly influence offspring fitness; however, the importance of female identity to offspring size determination is poorly understood, despite the potential for identity effects to drive offspring size adaptation and population dynamics. We tracked reproductive investment (skein mass) and mean egg diameter, mass, and density prod...

The Laurentian Great Lakes of North America provide valuable ecosystem services, including fisheries, to the surrounding population. Given the prevalence of other anthropogenic stressors that have historically affected the fisheries of the Great Lakes (e.g., eutrophication, invasive species, overfishing), climate change is often viewed as a long-te...

Genetic diversity has been hypothesized to promote fitness of individuals and populations, but few studies have examined how genetic diversity varies with ontogeny. We examined patterns in population and individual genetic diversity and the effect of genetic diversity on individual fitness among life stages (adults and juveniles) and populations of...

Trade-offs among growth, mortality, and reproduction form the basis of life history theory but may vary among populations owing to local ecological conditions. We examined life history trade-offs driving variation in maturation among 13 yellow perch (Perca flavescens) stocks in the Great Lakes using sex-specific age and length at 50% maturity (A50...

The composition and structure of fish communities are affected by a variety of factors, both within the aquatic ecosystem and from the surrounding watershed. Many studies have examined what structures fish assemblages over broad spatial and environmental gradients. However, the influence of local environmental attributes on the observed variation i...

Offspring size determines offspring survival rates; thus, understanding factors influencing offspring size variability could elucidate variation in population dynamics. Offspring size variation is influenced through multigenerational adaptation to local environments and within-lifetime plastic responses to environmental variability and maternal eff...

Female yellow perch Perca flavescens exposed to three overwinter temperature regimes (4, 8 and 13° C) for 150 days spawned in markedly different proportions upon spring warming (37% of females in 4° C v. 64 and 91% in 8 and 13° C treatments, respectively), but exhibited no differences in fecundity, egg size or egg lipid content. Females held at 4°...

A variety of gears and analytical methods can be used to characterise lentic fish assemblages; however, the combined influence of gear type and analysis can affect conclusions about assemblage patterns. Fish assemblages sampled with night electric fishing, gillnets and trapnets from 153 lakes were evaluated using summary indices of species composit...

Reproductive investment (e.g., egg size) is generally critical for the successful establishment of invasive species, with high variability often positively influencing success. Silver carp Hypophthalmichthys molitrix (Valenciennes, 1844) are highly successful invasive fish on a global scale and threaten biodiversity in a wide range of freshwater ha...

Fish stock-recruitment dynamics may be difficult to elucidate because of nonstationary relationships resulting from shifting environmental conditions and fluctuations in important vital rates such as individual growth or maturation. The Great Lakes have experienced environmental stressors that may have changed population demographics and stock-recr...

The large percids, including Perca and Sander species, are economically and ecologically important species that inhabit large temperature regions of the Northern Hemisphere. In this chapter, we provide an overview of the environmental biology of the Perca (including yellow perch P. fl avescens and Eurasian perch P. fl uviatilis) and Sander (includi...

Egg size is influenced through complex interplay of long-term adaptation to local environments and short-term plastic responses to annual variability. Maternal effects also play a potentially important role, as larger females appear to produce larger, better-provisioned offspring than smaller females. Superimposed on egg size variation among stocks...

Maternal effects have been observed to interact with genotypic and environmental influences to structure offspring phenotypes across a wide variety of taxa. In fishes, maternal effects may be especially important due to their potential influence on development and survival during early ontogeny – a period with high potential for population regulati...

Rainbow smelt Osmerus mordax represent an important prey for several recreationally valuable piscivores in the Great Lakes and support locally important fisheries throughout the region. However, rainbow smelt populations have suffered steep declines in abundance over the past two decades, which may be associated with prolonged poor recruitment succ...

The White Bass Morone chrysops is a popular sport fish that appears to be negatively affected by invasions of White Perch M. americana and often declines or disappears from invaded systems. In 2008, the first discovery of White Perch in Lake James, North Carolina, provided a rare opportunity to investigate trophic overlap between White Perch and a...

The trophic dynamics of invasive species can yield insights into the mechanisms of invasion success and aid in the prediction of potential impacts on established species. Additionally, the predicted effects of an invader may differ depending on how it integrates into the resident food web and whether its resource use changes throughout the invasion...

Lake characteristics (biological, chemical, and physical) have strong influences on the structure of fish communities. Although each lake is unique, in general, lakes have common features that contribute to and help predict fish diversity and create novel managerial conditions. Description and classification of lake fish communities based on influe...

Successful invasive species must pass through several invasion stages, and life history or trophic strategies allowing for successful transitions may change as the species advances from one stage to the next. To evaluate the role of life history shifts in the invasion success of white perch (Morone americana), age and length at maturity, gonadosoma...

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 pro...

To successfully establish in new systems, invasive species must pass through several invasion stages, and life history traits that facilitate successful transitions may change as the species advances through each stage. Demographic data for species at each stage can be pivotal to understanding and predicting invasions and their effects. White perch...