Walleye Recruitment Research Articles

Unraveling the ecological impacts of alewife in a large Midwest reservoir decades after introduction

Alewives Alosa pseudoharengus are native to the Atlantic Coast but have been introduced to inland waters as forage for sportfish populations. Alewife introductions have benefitted sportfish growth and body condition but have also negatively influenced larval fish survival through predation or competition for zooplankton. In 1986, alewives were stocked into Lake McConaughy, Nebraska, and became abundant and self-sustaining shortly thereafter. It has since been hypothesized that the alewife introduction altered zooplankton size and species composition and potentially negatively influenced Walleye recruitment. However, no studies on alewife distribution or food habits have been conducted on Lake McConaughy to date to investigate the potential influences of alewife on the fish and zooplankton communities. We collected alewives in the nearshore areas of Lake McConaughy during May–July 2022 and 2023 using short-term (about 1 h) small mesh horizontal gill net sets. We spatially assessed alewives by sampling the north and side south sides in addition to four classified quadrants of the reservoir. Total lengths (mm) were recorded, and stomachs were collected from up to 20 alewife per net. Prey were identified and food habits were summarized as percent composition by number. Zooplankton consumption was also paired with vertical Wisconsin zooplankton net tows taken at each site to assess prey selectivity. There was no evidence of piscivory suggesting that alewife predation is not influencing fish recruitment in Lake McConaughy. Alewives almost exclusively consumed zooplankton throughout the study period, suggesting the potential for interspecific competition with young-of-year fish. Our research provides a greater understanding of how introducing a non-native prey species to benefit sport fishes may have unintended negative consequences.

Biotic and abiotic factors that influence Walleye recruitment in stocked lakes in Michigan

AbstractObjectiveIn recent decades, widespread evidence of declining Walleye Sander vitreus recruitment in the Midwestern United States has raised concerns about diminishing ecological benefits and fishing opportunities, which in turn has resulted in natural resource agencies using stocking to supplement populations. Success of Walleye stocking events vary; thus, evaluating the external factors that influence recruitment success of Walleye resulting from stocking or natural production is critical for improved management.MethodsWe evaluated factors influencing the relative recruitment in 98 lakes stocked annually with Walleye by integrating 20 years of stocking data with fisheries assessment and abiotic data. We indexed recruitment as the relative abundance of Walleye cohorts from natural and stocked sources combined and used boosted regression tree modeling to identify variables that are associated with varying recruitment.ResultGrowing degree‐days at age 1, shoreline development index, mean depth, and degree‐days at age 2 were the most important variables. The boosted regression tree model explained 17% of observed variability in recruitment. A positive relationship between growing degree‐days and Walleye recruitment was observed, whereas shoreline development and lake depth had a negative relationship with recruitment. Secondarily important predictors were lake surface area, spring warming rate, Northern Pike Esox lucius abundance, and degree‐days at age 0. In general, Walleye recruitment was positively associated with these predictors, with the exceptions of spring warming rates >0.3°C/day and being exposed to >3500 degree‐days at age 0.ConclusionOur results indicate that thermal variables in addition to lake characteristics are important recruitment drivers in stocked waters and highlights the potential for resource managers to use this information to prioritize stocking efforts in temperate lakes.

Rainbow smelt (Osmerus mordax) influence on walleye (Sander vitreus) recruitment decline: mtDNA evidence supporting the predation hypothesis.

Rainbow smelt (Osmerus mordax) have been introduced widely but are associated with declines in walleye (Sander vitreus) recruitment. A primary hypothesis for these declines is that O. mordax consume larval S. vitreus. We confirmed overlapping spatial-temporal distributions of larval S. vitreus and O. mordax in our study system and used mtDNA analyses to determine if O. mordax stomach contents contained S. vitreus. Approximately 20% of O. mordax composite stomach samples were considered positive for S. vitreus consumption. These findings support the predation hypothesis and have S. vitreus management/stocking implications.

Food web changes reflected in age‐0 piscivore diets and growth

AbstractLake Erie walleye (Stizostedion vitreum) recruitment fluctuates annually and depends partially on their diet and growth during their first year of life. In recent decades, age‐0 walleye diet and growth may be responding to food web changes in western Lake Erie. To determine how age‐0 walleye have responded to changes in prey species and abundance, we compared diet between 2019, 2014 and 1994–1999. Larval walleye ate predominantly cyclopoids in 2019, compared to 1994–1999 when calanoids were the most consumed copepod. Juvenile walleye ate predominantly large cladocerans and benthic invertebrates in 2019, compared to 2014 and 1994 when fish was the most consumed prey. Additionally, in 2019 and 2014, age‐0 walleye ate two of the current aquatic invasive species (AIS), Bythotrephes longimanus and Neogobius melanostomus, and the historical AIS, Osmerus mordax. Age‐0 walleye were smaller in 2019 than in 2014 and switched to consuming more AIS and less fish suggesting that more energetically favourable prey were not available. While age‐0 walleye showed adaptation to new prey and conditions, they had a lower quality diet because they consumed less fish, but also because the invasive fish they now consume have a lower energy density than native species. However, lower quality diet and size may not result in reduced survival, if adequate alternative prey is available. Continued monitoring of age‐0 walleye diet could provide confirmation that lower diet quality during the first year decreased walleye growth and aid to identify any effects changes in age‐0 diets has on recruitment to the adult population.

Depensation in fish recruitment driven by context-dependent interactions with another predator

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, Percidae) populations in Wisconsin identified by Sass et al., (2021), we tested for potential abiotic and biotic predictors of walleye recruitment depensation. The best fitting model contained covariates for climate, land cover, and fish community composition, all interacting with the relative abundance of largemouth bass (Micropterus salmoides, Centrarchidae). The consistent interaction effect of largemouth bass across the other covariates suggests a key role of this species in regulating walleye recruitment dynamics at low population size. The risk of depensation was negatively correlated with largemouth bass abundance in our dataset, pointing towards continued challenges for walleye populations given the increasingly favorable social and environmental conditions for largemouth bass. Using the model, vulnerability to depensation was predicted for an additional 115 walleye lakes with insufficient data to directly estimate the risk of depensation. Predictions suggested that 73 prediction lakes are vulnerable to depensatory recruitment should population sizes significantly decrease. This predictive framework could be used to prioritize lakes for different management actions based on depensation strength and average adult population size. Lakes with low walleye abundances, but low risk of depensation, may be more likely to respond positively to management efforts and are likely better candidates than those where depensation effects are likely strong when abundance is low.

Synthesizing Professional Opinion and Published Science to Build a Conceptual Model of Walleye Recruitment

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. We used a systematic literature review, a survey, and a workshop attended by professionals with expertise in recruitment of WalleyeSander vitreusto identify common environmental drivers of Walleye recruitment and additional sources of variation (i.e., context dependencies) among populations. The importance of individual environmental drivers, as well as the direction of their influence, differed as a function of geographic region, lake surface area, and Walleye life stage. The literature suggested abiotic conditions (e.g., temperature) during the first year of life were influential in determining recruitment. Professional opinion noted the importance of biotic factors, with prey availability and predation risk having the most consistent relationships with recruitment. We synthesized this information to propose a conceptual model that illustrates the suite of characteristics that shape Walleye recruitment over large spatial and temporal scales. Our findings emphasize the importance of first‐year growth and system‐specific contextual factors, which can alter the relative importance of the environmental drivers of recruitment.

Black Crappie Influences on Walleye Natural Recruitment in Northern Wisconsin Lakes

AbstractWalleye 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 effects on recruit survival. Previous research in other systems has suggested that White Crappie Pomoxis annularis negatively influence Walleye recruitment, but interactions between Walleye recruitment and Black Crappie Pomoxis nigromaculatus have not been examined. We evaluated trends between Black Crappie and age‐0 Walleye relative abundance (catch per effort [CPE]) collected in northern Wisconsin during 1991–2017. Specifically, we tested for (1) trends in age‐0 Walleye and Black Crappie CPE over time, (2) a relationship between age‐0 Walleye and Black Crappie CPE, and (3) the influence of several abiotic and biotic covariates (including Black Crappie CPE) on age‐0 Walleye recruitment. Age‐0 Walleye CPE declined and Black Crappie CPE increased significantly during 1991–2017. Within lakes, the relationship between age‐0 Walleye and Black Crappie CPE showed a threshold effect such that age‐0 Walleye CPE was always low when Black Crappie CPE was high. Of the abiotic and biotic covariates tested to explain variability in the age‐0 Walleye and Black Crappie CPE relationship, only Black Crappie CPE was significant. Our results suggest that Black Crappie may negatively influence Walleye natural recruitment; however, we caution that our findings only reveal a pattern and not a mechanistic explanation for negative interactions between the species. Additional research is needed to test for mechanistic interactions between Walleye and Black Crappie and to inform comanagement of these species.

Correction: Drivers of walleye recruitment in Minnesota’s large lakes

Correction: Drivers of walleye recruitment in Minnesota’s large lakes

Resisting ecosystem transformation through an intensive whole‐lake fish removal experiment

AbstractLake 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 species and concurrent increases in warm‐water fishes (e.g. Centrarchidae) may have contributed to declines. To test the utility of an intensive management action to resist walleye loss, an experimental removal of ~285,000 centrarchids from a 33‐ha lake over 4 years was conducted while monitoring the fish community response. Centrarchid abundance declined and yellow perch Perca flavescens (Mitchill) increased, yet no evidence of walleye recruitment was observed. These findings explore the feasibility of intensive resistance as a management strategy in supporting walleye facing environmental change and provide a platform for management discussions to move beyond resist strategies in the Resist‐Accept‐Direct (RAD) framework to navigate ecosystem change.

It’s Complicated and It Depends: A Review of the Effects of Ecosystem Changes on Walleye and Yellow Perch Populations in North America

AbstractWalleye Sander vitreus and Yellow Perch Perca flavescens are culturally, economically, and ecologically significant fish species in North America that are affected by drivers of global change. Here, we review and synthesize the published literature documenting the effects of ecosystem changes on Walleye and Yellow Perch. We focus on four drivers: climate (including temperature and precipitation), aquatic invasive species, land use and nutrient loading, and water clarity. We identified 1,232 tests from 370 papers, split evenly between Walleye (n = 613) and Yellow Perch (n = 619). Climate was the most frequently studied driver (n = 572), and growth or condition was the most frequently studied response (n = 297). The most commonly reported relationship was “no effect” (42% of analyses), usually because multiple variables were tested and only a few were found to be significant. Overall responses varied among studies for most species‐response–driver combinations. For example, the influence of invasive species on growth of both Walleye and Yellow Perch was approximately equally likely to be positive, negative, or have no effect. Even when results were variable, important patterns emerged; for example, growth responses of both species to temperature were variable, but very few negative responses were observed. A few relationships were relatively consistent across studies. Invasive species were negatively associated with Walleye recruitment and abundance, and higher water clarity was negatively associated with Walleye abundance, biomass, and production. Some variability in responses may be due to differences in methodology or the range of variables studied; others represent true context dependence, where the effect of a driver depends on the influence of other variables. Using common metrics of impact, publishing negative results, and robust analytical approaches could facilitate comparisons among systems and provide a more comprehensive understanding of the responses of Walleye and Yellow Perch to ecosystem change.

Similar Environmental Conditions are Associated with Walleye and Yellow Perch Recruitment Success in Wisconsin Lakes

AbstractSince the mid‐2000s, recruitment of WalleyeSander vitreusin some northern Wisconsin lakes has declined, potentially because of climate‐induced changes in lake environments. Yellow PerchPerca flavescensis also an ecologically and culturally important fish species in this region, but mechanisms driving Yellow Perch recruitment are unclear because of a lack of targeted sampling. Previous studies have suggested that recruitment of these two species may be regulated by similar factors, and observed declines in Walleye recruitment may be cause for concern about Yellow Perch recruitment. Our objectives were to determine if abiotic factors related to recruitment success were similar between Walleye and Yellow Perch populations in northern Wisconsin lakes and if the probability of successful Walleye recruitment was related to estimates of juvenile Yellow Perch abundance before Walleye recruitment declines were observed. We addressed these objectives using historical data from Wisconsin lakes. Random forest analysis incorporating lake‐specific averages of predictor variables indicated that winter conditions (duration or severity), growing degree days, variation in spring temperatures, peak summer temperature, and Secchi depth were important predictors of recruitment success for both species. Logistic regression indicated that before Walleye recruitment declines were observed on some lakes (2000–2006), Walleye recruitment success was related to relative abundance of juvenile Yellow Perch in mini‐fyke‐net sampling. Our results indicate that landscape‐level patterns in recruitment success for the two species are likely similar and additional research to understand Yellow Perch recruitment trends is warranted. Better information on Yellow Perch recruitment could contribute to a better understanding of Walleye recruitment trends as declines in Yellow Perch could influence prey availability and survival of age‐0 Walleye. Furthermore, potential declines in Yellow Perch could lead to changes in the numbers and size of Yellow Perch caught by anglers, which may have implications for harvest management.

Evaluation of Walleye Minimum Length Limits with Changing Water Regimes in the Great Plains

AbstractAbove‐normal precipitation in the 1990s resulted in new waters and Walleye Sander vitreus fisheries across northeastern South Dakota. Concerns with overharvest led to the implementation of a Walleye minimum length limit (MLL) on many new fisheries, but over time most of the MLLs were removed. We were interested in knowing why the MLLs failed. We compared Walleye gill‐net data and angler creel data under rising and declining water regimes and between periods with and without an MLL regulation in two new waters (Bitter Lake and Waubay Lake). We also assessed Walleye annual recruitment and growth patterns and examined if water regimes, MLLs, or Walleye recruitment were potential drivers of Walleye relative abundance, growth, and size structure. Few differences were found across water regimes and between periods with and without an MLL. At Bitter Lake, significant differences were identified across water regimes for the number of age‐3 Walleyes per gill net, Walleye proportional size distribution of preferred length (PSD‐P), angling pressure, and angler catch rates of Walleyes. Walleye relative weight and PSD‐P significantly differed between water regimes at Waubay Lake. Mean length at capture for age‐3 Walleyes and proportional size distribution were significantly different between periods having an MLL and no MLL at Bitter Lake. At Waubay Lake, Walleye gill‐net CPUE (number/gill net) and PSD‐P significantly differed between periods with and without an MLL. Water regimes, MLL, and Walleye recruitment were not identified as strong drivers of Walleye population characteristics. Recruitment was variable in each lake (Bitter Lake age‐3 CPUE CV = 148%, Waubay Lake age‐3 CPUE CV = 166%), with occasional strong cohorts recruiting. We believe recruitment dynamics influenced Walleye abundance and growth, which led to the removal of MLLs from each lake. Knowledge concerning Walleye population recruitment dynamics and growth is important when implementing MLLs and evaluating their effectiveness.

Evidence that copepod biomass during the larval period regulates recruitment of Lake Erie walleye

Walleye (Sander vitreus) is an economically and culturally important species in Lake Erie that has experienced large interannual variability in recruitment. We examined the importance of prey biomass during the larval period to walleye recruitment while also considering the importance of temperature. Using nine years of field data over a 22-year period (1994–2016) for larval walleye and zooplankton, we found that strong recruitment events occurred in years when the biomass (dry µg L-1) of copepods (e.g., calanoids, cyclopoids) was greater during the spring larval period. Conversely, the biomass of cladocerans and mean spring water temperatures were poor predictors of walleye recruitment. Our results highlight the need to consider zooplankton availability during the larval period when seeking to understand the recruitment dynamics of freshwater fish populations such as Lake Erie walleye.

Recruitment Bottlenecks for Age‐0 Walleye in Northern Wisconsin Lakes

AbstractSome northern Wisconsin lakes have shown declines in catches of age‐0 Walleye Sander vitreus in standardized fall electrofishing sampling, suggesting that recruitment bottlenecks are occurring in the first several months of life. In 2016 and 2017, we sampled six lakes with declining trends in natural Walleye recruitment (D‐NR lakes) and seven lakes with a history of sustained natural recruitment (S‐NR lakes) to determine if timing of potential recruitment bottlenecks for age‐0 Walleye were consistent among D‐NR lakes and if abiotic and biotic metrics differed between D‐NR and S‐NR lakes. We also examined diets of larval Walleye to assess prey items that may be important to early growth and survival and to determine if occurrence of piscivory was related to larval Walleye total length. Differential patterns in the presence and absence of age‐0 Walleye at different life history stages in the first 6 months of life suggested that recruitment bottlenecks in D‐NR lakes were consistently occurring before mid‐July (five of six lakes). Mean Secchi depth, surface conductivity, abundance of larval Yellow Perch Perca flavescens, and most metrics of zooplankton abundance and mean size were similar between D‐NR and S‐NR lakes. Log10 transformed number of adult Walleye per hectare was lower and adult mean total length was higher in D‐NR lakes. Across all lakes, diets of larval Walleye consisted of zooplankton and larval fish and the occurrence of piscivory was higher than reported in previous studies and was positively related to total length of larval Walleye. Causes of recruitment bottlenecks in D‐NR lakes remain unclear, making it difficult to identify management actions that might be implemented to circumvent these bottlenecks. However, our results indicate that future research should focus on the period between egg deposition and mid‐July.

Effects of Reservoir Elevation and Spatial Synchrony on Walleye Recruitment in Lake Oahe, Missouri River

AbstractRecruitment is an important driver of fish population abundance and size structure and can be affected by a variety of density‐dependent and density‐independent factors. Walleye Sander vitreus populations often exhibit variable year‐class strength, which has been attributed to a suite of factors. In this study, we quantified variability in Walleye recruitment, assessed within‐lake recruitment synchrony, and modeled recruitment variability for year‐classes that were produced from 1988 to 2013 in Lake Oahe, a large Missouri River reservoir. The objectives of this study were to determine (1) whether Walleye recruit annually, (2) whether Walleye recruitment is spatially synchronous, and (3) whether Walleye recruitment is better described by biotic or abiotic factors. The variability of Walleye recruitment was indexed by using gill‐net catch of age‐2 Walleye across nine locations in Lake Oahe, and factors affecting recruitment were evaluated by using stock–recruit analysis. Over the 26 years that were assessed, all year‐classes were present and four exceptionally large year‐classes were produced. Recruitment synchrony was apparent among locations within Lake Oahe, but this relationship was largely influenced by the spatial synchrony of the four exceptionally large year‐classes and was no longer detectable when those year‐classes were removed. The relative abundance of age‐4 and older Walleye, taken as an index of spawner abundance, was a poor predictor of Walleye recruitment, indicating that Walleye recruitment was regulated by density‐independent factors across the range of observations. The interactive effects of reservoir elevation and elevation change improved model fit to explain 59% of the recruitment variation and indicated that increased elevation from the previous year improved recruitment. Our results indicate that Walleye recruitment may be favored by increasing the water levels in the reservoir in spring.

Drivers of walleye recruitment in Minnesota’s large lakes

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 Minnesota’s nine largest inland lakes. Our model explained 20% of the variation in year-class strength overall, with predictive performance varying among lakes (–8% to 37% explained variance). Of the variables analyzed, degree-days during the first year of life and first winter severity were the most important for predicting recruitment, with relatively weak year classes predicted to occur with cold first growing seasons and severe first winters. Other thermal variables were secondarily important predictors of year-class strength. Predicted year-class strength was positively related to stock size and stocking and negatively related to the presence of invasive species; however, these variables were less important than thermal variables. Our results indicate that thermal conditions in early life can have a substantial impact on walleye recruitment and highlight the potential for differing recruitment drivers and dynamics among lakes.

Crustacean zooplankton available for larval walleyes in a Lake Michigan embayment

Adequate densities of zooplankton prey are critical for growth and survival of larvae of many fish species. Little information exists on the density of zooplankton in Great Lakes inshore areas during early spring, when larvae of important fishes rely on zooplankton. Reduced age-0 walleye recruitment and the absence of data on zooplankton availability for larval walleyes in northern Green Bay, Lake Michigan, led us to assess zooplankton densities during this critical spring period. We conducted biweekly vertical plankton tows in 2014–2016 near reefs and river plumes used by spawning walleyes for periods when larval walleyes were expected to be relying on zooplankton prey. Densities of zooplankton were well below literature values identified for good growth and survival of larval walleyes, averaging 1.5 individuals L−1 for all taxa and 0.12 individuals L−1 for large-bodied taxa across all sites and sampling dates. Various factors could contribute to the low density of zooplankton observed. We found low but significantly higher densities of cyclopoid copepods, nauplii, Bosmina, and total zooplankton at river mouth sites compared to open water sites. These results suggest that food availability for larval walleye in our study area was severely limiting which is consistent with the paucity of strong year classes observed since 2000. We suspect northern Green Bay has limited potential for producing strong year classes of walleyes under such conditions. Fishery managers working in unproductive waters should consider assessing the zooplankton community during critical periods to identify potential bottlenecks to reproductive success and larval fish survival.

Walleye inland lake habitat: considerations for successful natural recruitment and stocking in North Central North America

Raabe JK, VanDeHey JA, Zentner DL, Cross TK, Sass GG. 2019. Walleye inland lake habitat: considerations for successful natural recruitment and stocking in North Central North America. Lake Reserve Manage. 36:335–359. Walleye (Sander vitreus) occur naturally or through extensive introductions in many inland lakes (i.e., non-Laurentian Great Lakes) throughout North Central North America. Persistence of walleye in these systems is influenced by factors including habitat, species interactions, exploitation, and stocking. Managers have expressed concerns about recent declining walleye recruitment and abundance in many inland populations, despite various conservation efforts (e.g., stocking, regulations). Therefore, we synthesized the scientific literature to provide information on how habitat influences successful natural recruitment and stocking. Historical and more recent studies indicate walleye are most successful in coolwater, mesotrophic, intermediate-to-large (>100 ha) lakes and that they spawn close to shore, in shallow water, and predominately over gravel and cobble substrates. Recent studies suggest that age-0 recruitment bottlenecks are likely occurring between hatching and midsummer. Relatedly, survival of stocked walleye tends to be higher for large fingerlings over fry or small fingerlings. Modeling studies indicate walleye declines may be attributed to warmer water and increasing water clarity, especially in smaller lakes or those with higher Centrarchidae or northern pike (Esox lucius) abundance. Important future walleye research includes connecting spawning habitat quality and quantity with hatching and recruitment success and continued evaluation of influential factors in the first year and later life stages. Management should focus on identifying and protecting high quality lakes and important habitats (e.g., spawning), along with understanding habitat and biological factors to determine whether walleye populations can be improved (e.g., habitat projects, stocking, regulations) or in some cases not managed for altogether (e.g., too warm).

Eroding productivity of walleye populations in northern Wisconsin lakes

Managing fisheries through rapid environmental change requires diverse approaches for identifying and adapting to novel ecological conditions. For the Wisconsin Ceded Territory, we calculated 473 adult walleye (Sander vitreus) production (P), biomass (B), and P/B estimates for 1990–2012. Frequency distributions for production statistics were right-skewed, indicating the fishery is generally dominated by low production populations. Mean P, B, and P/B were significantly elevated in natural recruitment (NR) lakes compared with combination (NR + stocking) and stocked-only lakes. Furthermore, combination populations had significantly higher production compared with stocked-only lakes. In NR lakes, walleye productivity changed little over time; however, the proportion of NR populations has declined over time. In combination and stocked-only populations, there were significant temporal declines in P, B, and P/B, and the proportion of these lakes has increased through time. This study reveals the crucial link between fish recruitment potential and fish production, helping to explain why the regional walleye fishery is struggling. Causes for walleye recruitment and production declines remain unclear, but long-term shifts in fish habitats are likely involved (e.g., from climate change and indirect food web effects). Decreasing walleye production is an important and emerging fishery management challenge in the region and portends a need to adapt fisheries management systems collaboratively for future sustainability.

Maternal effects better predict walleye recruitment in Escanaba Lake, Wisconsin, 1957–2015: implications for regulations

Maternal influences on age-0 walleye (Sander vitreus (Mitchill, 1818)) recruit abundance and survival from egg to fall were observed in Escanaba Lake, Wisconsin, in 1957–2015. Annual egg production best explained variation in age-0 recruitment, compared with female relative abundance, and adult abundance (sexes combined). Age-0 recruitment was not significantly correlated with any temperature metric tested or our index of yellow perch (Perca flavescens (Mitchill, 1814)) abundance. Survival of walleye from egg to fall age-0 was positively correlated with the percent contribution of large females (>55.9 cm) to annual egg production. Mean size diversity of females by length class did not influence age-0 recruit abundance or survival over time. Evidence for maternal effects via size- and age-specific influences on fecundity and age-0 walleye survival suggest that exploitation may influence natural recruitment by altering adult female size structure. Given recent declines observed in walleye natural recruitment in the upper Midwestern USA, understanding the roles of maternal drivers and exploitation on recruitment is critical for sustainable walleye management.