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Knowledge of environments used during early life history and movement patterns of Bighead Carp (Hypophthalmichthys nobilis) and Silver Carp (H. molitrix), collectively termed bigheaded carps, in the Upper Mississippi River (UMR) would be valuable for informing control measures to limit further population expansion and impacts of these species. Lock and Dam 19 (LD19) is a high-head dam on the UMR that delineates downriver areas where bigheaded carps are well established from upriver pools where these species are less abundant and evidence of reproduction and recruitment are limited. Principal natal environments supporting recruitment of emerging bigheaded carp populations in the UMR are unknown. The objectives of this study were to (1) infer environments occupied during early-life stages by bigheaded carps collected in UMR Pools 19-21 during 2013-2014 using otolith microchemistry and stable isotope analyses, and (2) use early-life environment assignments and capture location to identify individuals that passed through LD19. Differences in multivariate water chemistry signatures (Sr:Ca, Ba:Ca and δ18O) among the UMR, its tributaries, and the Missouri and Middle Mississippi rivers enabled development of a classification model for inferring early-life environment of bigheaded carps. Multiple sources of recruits, including from tributaries, have contributed to upriver expansion of bigheaded carps in the UMR. Sustainable control of bigheaded carps upstream of LD19 will likely require efforts to control local recruitment and immigration from downriver. The frequency of bigheaded carps collected in Pool 19 that were downstream of LD19 during early life suggests that bigheaded carps upstream of LD19 still predominantly consisted of immigrants from downriver during 2013-2014. Otolith chemistry provides an approach for assessing the extent to which changes in abundance of bigheaded carps upstream of LD19 are associated with local recruitment or immigration from downriver.

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Abstract. Moderation of stream temperatures by riparian shading and groundwater are known to promote growth and survival of salmonid fishes, but effects of riparian shade and groundwater on to be growth of warmwater stream fishes are poorly understood or assumed to be negligible. We used stream temperature models to relate shading from riparian vegetation and groundwater inflow to summer water temperatures in Missouri Ozark streams and evaluated effects of summer water temperatures on smallmouth bass, Micropterus dolomieu, growth using a bioenergetics model. Bioenergetics model simulations revealed that adult smallmouth bass in non-spring-fed streams have lower growth potential during summer than fish in spring-fed streams, are subject to mass loss when stream temperatures exceed 278C, and will likely exhibit greater interannual variation in growth during summer if all growth-influencing factors, other than temperature, are identical between the two stream types. Temperature models indicated that increased riparian shading will expand the longitudinal extent of thermal habitat capable of supporting adult smallmouth bass growth in spring-fed stream reaches when mean daily air temperatures exceed 278C. Optimum growth temperature (228C) will be present only in spring-fed streams under these conditions. Potential for increasing shade through riparian restoration is greatest for streams ,5 m wide and along north-south reaches of larger streams. However, temperature models also indicated that restoring riparian shading to maximum levels throughout a watershed would increase the total stream mileage capable of supporting positive growth of adult smallmouth bass by only 1-6% when air temperatures are at or near average summer maxima; increases in suitable thermal habitat would be greatest in watersheds with higher spring densities. Riparian management for maintenance or restoration of the thermal habitat of adult smallmouth bass during summer should be focused in areas strongly influenced by groundwater. Restoring riparian shading along spring-fed warmwater streams will likely benefit adult smallmouth bass growth and may ultimately influence population sizes.

Data from laboratory evaluations of seven fish bioenergetics models (BEMs) were used to investigate possible associations between BEM prediction error in relative growth rate (RGR error ) and levels of model input variables: mean daily food-consumption rate and fish body weight. Correlation between RGR error and fish body weight was found in three BEMs applied under submaintenance feeding conditions. A strong correlation between RGR error and mean daily consumption level was observed in all models over full consumption ranges; consumption level explained 70%-96% of variation in RGR error . All BEMs underestimated (by 2-to 5-fold) growth at lower consumption levels and overestimated (by 2-to 3-fold) growth at higher consumption levels. RGR error values associated with higher consumption levels were greater (up to 22 cal·g -1 ·day -1 ) than those at lower consumption levels (up to 10 cal·g -1 ·day -1 ). Correlation between consumption rate and RGR error in all seven models indicates widespread systematic error among BEMs that likely arises from deficiencies in consumption-dependent model parameters. Results indicate that many BEMs are substantially inaccurate when predicting fish growth from higher feeding rates or estimating consumption from higher growth rates, even when higher consumption levels or growth episodes are of short duration. Findings obtained under submaintenance feeding conditions indicate that additional body-weight-and consumption-dependent terms should be added to BEM subequations for routine metabolism to account for metabolic reduction.Résumé : Les données des évaluations en laboratoire de sept modèles bioénergétiques (BEM) de poissons nous ont servi à étudier les associations possibles entre l'erreur de prédiction par les BEM du taux relatif de croissance (RGR erreur ), d'une part, et la valeur des variables d'entrée des modèles, soit le taux journalier moyen de consommation de nourriture et la masse corporelle des poissons, d'autre part. Il existe une corrélation entre RGR erreur et la masse corporelle des poissons dans trois des BEM utilisés dans des conditions d'alimentation inférieures au niveau de maintien (SMFC). Il y a aussi une forte corrélation entre RGR erreur et le taux journalier moyen de consommation dans tous les modèles sur toute l'étendue des taux de consommation; le taux de consommation explique 70 -96 % de la variation de RGR erreur . Tous les BEM sous-estiment la croissance (par un facteur de 2-5) aux faibles taux de consommation et la surestiment (par un facteur de 2-3) aux taux de consommation plus élevés. Les RGR erreur associées aux taux plus élevés de consommation sont plus grandes (pouvant atteindre 22 cal·g -1 ·jour -1 ) que celles liées aux taux de consommation plus faibles (atteignant 10 cal·g -1 ·jour -1 ). La corrélation entre le taux de consommation et RGR erreur dans les sept modèles indique qu'il y a une erreur systématique générale dans les BEM qui provient vraisemblablement d'imprécisions des paramètres des modèles reliés à la consommation. Nos rés...

Laboratory growth and food consumption data for two size classes of age 2 year yellow perch Perca flavescens, each fed on two distinct feeding schedules at 21° C, were used to evaluate the abilities of the Wisconsin (WI) and Karas–Thoresson (KT) bioenergetics models to predict fish growth and cumulative consumption. Neither model exhibited consistently better performance for predicting fish body masses across all four fish size and feeding regime combinations. Results indicated deficiencies in estimates of resting routine metabolism by both models. Both the WI and KT models exhibited errors for predicting growth rates, which were strongly correlated with food consumption rate. Consumption‐dependent prediction errors may be common in bioenergetics models and are probably the result of deficiencies in parameter values or assumptions within the models for calculating energy costs of specific dynamic action, feeding activity metabolism or egestion and excretion. Inter‐model differences in growth and consumption predictions were primarily the result of differences in egestion and excretion costs calculated by the two models. The results highlighted the potential importance of parameters describing egestion and excretion costs to the accuracy of bioenergetics model predictions, even though bioenergetics models are generally regarded as being insensitive to these parameters. The findings strongly emphasize the utility and necessity of performing laboratory evaluations of all bioenergetics models for assurance of model accuracy and for facilitation of model refinement.

Nonnative fishes represent a significant impediment to the recovery of imperiled fishes, including those endemic to the Colorado River in the southwestern United States. Efforts to control nonindigenous fish abundance in the upper Colorado River basin have been unsuccessful owing in part to lack of knowledge regarding nonnative fish recruitment sources. We determined the source habitat (floodplain pond versus riverine habitats) for nonnative centrarchid fishes (largemouth bass Micropterus salmoides, green sunfish Lepomis cyanellus, bluegill L. macrochirus, and black crappie Pomoxis nigromaculatus) in the upper Colorado River using stable hydrogen isotopic composition (δD) and strontium: Calcium (Sr: Ca) ratios in fish otoliths as natural markers of environmental history. Stable hydrogen isotope analysis revealed that 59% of centrarchids exhibited the otolith core signatures expected for riverine‐origin fish, while 22% had emigrated from floodplain ponds and 19% were of uncertain origin. Strontium: Calcium ratio data were consistent with the δD assays and indicated that relatively few fish immigrated to the river from high‐salinity habitats. Black crappie was the only species that originated primarily from floodplain ponds. Efforts to control the abundance of most of the fishes included in this study should be concentrated in riverine habitats given the hydrologic conditions (below‐average river discharge) present during our study. However, the proportion of pond‐origin fish increased with fish age, which, coupled with historical river discharge data, suggested that floodplain pond contributions to riverine nonnative fish populations fluctuate with the interannual variations in flow regime and river‐pond connectivity. Our results are the first to demonstrate the utility of δD as a natural marker of fish environmental history that will probably provide valuable insights into the management of fish in other environments.

Knowledge of habitats used by fish throughout their life history is important for management and conservation of riverine fish populations and habitats. Naturally occurring chemical markers in otoliths have recently been used to determine natal origins and environmental history of fishes in a variety of marine and freshwater environments.However, to our knowledge no studies have examined the applicability of this technique in large floodplain rivers in the U.S.A. We evaluated otolith microchemistry and stable The ability to reconstruct environmental history of individual fish using naturally occurring isotopic markers in otoliths may also facilitate efforts to quantify nutrient and energy subsidies to the Illinois River provided by fishes that emigrate from floodplain lakes or tributaries.3