Invasive species represent a threat to aquatic ecosystems globally; however, impacts can be heterogenous across systems. Documented impacts of invasive zebra mussels (Dreissena polymorpha) and spiny water fleas (Bythotrephes cederströmii; hereafter Bythotrephes) on native fishes are variable and context dependent across locations and time periods. Here, we use a hierarchical Bayesian analysis of a 35-year dataset on two fish species from 9 lakes to demonstrate that early life growth of ecologically Electronic supplementary material The online version of this article (

Large‐scale ecological stressors such as climate change, habitat degradation, and invasive species increasingly affect fisheries across watershed or political boundaries within which they are typically managed. Though broad‐scale analyses of trends in fish populations and changes in aquatic communities can be useful for detecting the effects of these stressors, they are rarely possible due to a lack of long‐term data sets. The Minnesota Department of Natural Resources has used gill nets and trap nets to monitor fish communities in lakes since 1940, and the techniques have been standardized since 1970. We applied a random‐coefficient mixed‐effects model to mean CPUE data to describe statewide and local population trends of eight key fish species (Black Crappie Pomoxis nigromaculatus, Bluegill Lepomis macrochirus, Largemouth Bass Micropterus salmoides, Northern Pike Esox lucius, Smallmouth Bass M. dolomieu, Walleye Sander vitreus, White Sucker Catostomus commersonii, and Yellow Perch Perca flavescens) sampled from 1970 to 2013 in 119–1,499 lakes. We found increasing statewide trends in gill‐net CPUE of Black Crappie, Bluegill, Largemouth Bass, Smallmouth Bass, Northern Pike, and Walleye and decreasing trends for Yellow Perch and White Sucker. Statewide trends in average trap‐net CPUE were positive for Bluegill, negative for Black Crappie, Walleye, White Sucker, and Yellow Perch, and stable for Largemouth Bass, Northern Pike, and Smallmouth Bass. We compared the CPUE trends across lake types developed for Minnesota lakes and found some differences, especially in medium and large mesotrophic lakes, suggesting that some species display changes in abundance more in those lakes types than in others. This study quantifies temporal changes in Minnesota's fish community structure and can help managers focus future research and management activities in the state and in similar waters across central North America. Received May 14, 2014; accepted September 9, 2014

Eutrophication and climate warming are profoundly affecting fish in many freshwater lakes. Understanding the specific effects of these stressors is critical for development of effective adaptation and remediation strategies for conserving fish populations in a changing environment. Ecological niche models that incorporated the individual effects of nutrient concentration and climate were developed for 25 species of fish sampled in standard gillnet surveys from 1,577 Minnesota lakes. Lake phosphorus concentrations and climates were hindcasted to a pre-disturbance period of 1896–1925 using existing land use models and historical temperature data. Then historical fish assemblages were reconstructed using the ecological niche models. Substantial changes were noted when reconstructed fish assemblages were compared to those from the contemporary period (1981–2010). Disentangling the sometimes opposing, sometimes compounding, effects of eutrophication and climate warming was critical for understanding changes in fish assemblages. Reconstructed abundances of eutrophication-tolerant, warmwater taxa increased in prairie lakes that experienced significant eutrophication and climate warming. Eutrophication-intolerant, warmwater taxa abundance increased in forest lakes where primarily climate warming was the stressor. Coolwater fish declined in abundance in both ecoregions. Large changes in modeled abundance occurred when the effects of both climate and eutrophication operated in the same direction for some species. Conversely, the effects of climate warming and eutrophication operated in opposing directions for other species and dampened net changes in abundance. Quantifying the specific effects of climate and eutrophication will allow water resource managers to better understand how lakes have changed and provide expectations for sustainable fish assemblages in the future.

Catch rates of Yellow Perch Perca flavescens in standard gill-net surveys conducted by the Minnesota Department of Natural Resources have declined since 1970, but it is unclear whether this trend was due to reduced abundance or to changes in size structure affecting catchability. Because the minimum capture length of standard gill nets may limit effective sampling of some populations, the objectives of this study were to determine if length-based metrics could be used to characterize populations and their susceptibility to standard gill nets, if these metrics were correlated with a suite of abiotic and biotic variables, and if temporal trends in these metrics were evident. Data were collected from a broad size distribution of Yellow Perch sampled with standard gill nets, boat electrofishing, and small-mesh gill nets in 17 lakes. Estimated length at 50% maturity (L50) for females varied up to 100 mm across lakes, with values as small as 70 mm documented in some populations. Female L50 from supplemental gears was significantly positively correlated with the average length of the 15 largest fish (L max ) from all gears, and both of these metrics were positively correlated with standard gill-net catch. Exploratory analysis of female L50 indicated that this metric was positively correlated with latitude and lake size and negatively correlated with water clarity. Additionally, a statewide analysis of L max conducted with standard gill-net data from over 1,000 lakes found significant declines during the past 25 years, indicating that populations in Minnesota have likely shifted towards a smaller size structure, reducing catchability in standard gill nets. These results indicate that standard gill nets were ineffective for sampling some Yellow Perch populations and that length-based metrics such as L50 and L max can be used to infer catchability in standard gear and to monitor populations through time.Yellow Perch Perca flavescens are a percid species of management interest in the Upper Midwest region of the United States, occupying diverse lentic systems from the Great Lakes to glacial ponds. Yellow Perch fulfill dual ecological roles as a primary forage species for top predators, such as Walleye Sander vitreus (Johnson and Hale 1977) and Northern Pike Esox lucius (Pierce 2012), but are also piscivorous and targeted for harvest at larger

Two primary goals in fisheries research are to (1) understand how habitat and environmental conditions influence the distribution of fishes across the landscape, and (2) make predictions about how fish communities will respond to environmental and anthropogenic change. In inland, freshwater ecosystems, quantitative approaches traditionally used to accomplish these goals largely ignore the effects of species interactions (competition, predation, mutualism) on shaping community structure, potentially leading to erroneous conclusions regarding habitat associations and unrealistic predictions about species distributions. Using two contrasting case studies, we highlight how joint species distribution models (JSDMs) can address the aforementioned deficiencies by simultaneously quantifying the effects of abiotic habitat variables and species dependencies. In particular, we show that conditional predictions of species occurrence from JSDMs can better predict species presence/absence compared to predictions that ignore species dependencies. JSDMs also allow for the estimation of site-specific probabilities of species co-occurrence, which can be informative for generating hypotheses about species interactions. JSDMs provide a flexible framework that can be used to address a variety of questions in fisheries science and management.