Climate change is the defining environmental problem for our generation. The effects of climate change are increasingly evident and are anticipated to profoundly affect our ability to conserve fish habitats and fish assemblages. Reservoirs are important structures for coping with projected shifts in water supply, but they also provide refuge for riverine fishes and retain distinct fish assemblages that support diverse fisheries. The effects of climate change on reservoirs are unique among aquatic systems because reservoirs have distinctive habitat characteristics due to their terrestrial origin and strong linkage to catchments. This article reviews (1) the projected effects of rising temperature and shifting precipitation on reservoir fish habitats, and (2) adaptation strategies to cope with the anticipated effects. Climate warming impacts to reservoirs may include higher water temperatures and shifts in hydrology that can result in reduced water levels in summer and fall, altered water residence cycles, disconnection from upstream riverine habitats and backwaters, increased stratification, eutrophication, anoxia, and a general shift in biotic assemblages including plants, invertebrates, and fishes. What is needed to adapt to these changes is a perspective that focuses on maintaining ecosystem functionality rather than on retaining a certain species composition. To that end, various strategies organized into planning, monitoring, and managing compartments are identified.

Length limits have been implemented by fisheries management agencies to achieve population density, size structure, and angler satisfaction objectives. By redirecting harvest towards or away from particular length‐ or age‐groups, length limits rely on harvest by anglers to maintain a population at or near a desired state. The fish population changes that follow the implementation of harvest regulations may take several years to manifest, so long‐term monitoring may be needed to adequately evaluate length limits. We used an innovative application of cluster analysis to facilitate evaluation of the effects of three consecutive length limits on a population of Largemouth Bass Micropterus salmoides over a 28‐year period in Ross Barnett Reservoir, Mississippi. A 13–16‐in protected slot length limit (10 years), followed by a 15‐in minimum length limit (MLL; 11 years), followed by a 12‐in MLL (7 years) failed to restructure the Largemouth Bass population due to what we suggest was the expansion of a voluntary catch‐and‐release attitude that started in the first decade of the study period. Various population metrics shifted towards values expected in an unharvested population, and the observed shifts can be attributed to a harvest deficit created by the prevailing catch‐and‐release attitude. Largemouth Bass harvest regulations may no longer be relevant in many waters. The utility of regulations for restructuring Largemouth Bass populations is largely dependent on harvesting attitudes that vary geographically, depending on cultural characteristics and demographics. Received September 15, 2016; accepted March 15, 2017 Published online May 4, 2017

As the median age of the thousands of large reservoirs (> 200 ha) in the United States tops 50, many are showing various signs of fish habitat degradation. Our goal was to identify major factors degrading fish habitat in reservoirs across the country, and to explore regional degradation patterns. An online survey including 14 metrics was scored on a 0 (no degradation) to 5 (high degradation) point scale by 221 fisheries scientists (92% response rate) to describe degradation in 482 reservoirs randomly distributed throughout the continental United States. The highest scored sources of degradation were lack of aquatic macrophytes (41% of the reservoirs scored as 4–5), lack or loss of woody debris (35% scored 4–5), mistimed water level fluctuations (34% scored 4–5), and sedimentation (31% scored 4–5). Factor analysis identified five primary degradation factors that accounted for most of the variability in the 14 degradation metrics. The factors reflected siltation, structural habitat, eutrophication, water regime, and aquatic plants. Three degradation factors were driven principally by in-reservoir processes, whereas the other two were driven by inputs from the watershed. A comparison across U.S. regions indicated significant geographical differences in degradation relative to the factors emphasized by each region. Reservoirs sometimes have been dismissed as unnatural and disruptive, but they are a product of public policy, a critical feature of landscapes, and they cannot be overlooked if managers are to effectively conserve river systems. Protection and restoration of reservoir habitats may be enhanced with a broader perspective that includes watershed management, in addition to in reservoir activities. A medida que la edad media de cientos de grandes reservorios (> 200 ha) en los Estados Unidos de Norteamérica (EEUU) alcanza los 50 aṋos, muchos de ellos ya están presentando signos de degradación de hábitat para los peces. Nuestro objetivo fue identificar los principales factores que degradan el hábitat para los peces en los reservorios a lo largo del país, y explorar los patrones de degradación regional. Se realizó un sondeo en línea que incluye 14 medidas en una escala de 0 (sin degradación) a 5 (altamente degradado) a 221 científicos pesqueros (tasa de respuesta del 92%) para describir el grado de degradación de 482 reservorios distribuidos al azar a través de los EEUU. Las fuentes de degradación más destacables fueron la falta de macrofítas acuáticas (41% de los reservorios fueron calificados de 4 a 5), falta o pérdida de escombros de madera (35% se consideraron entre 4 y 5), fluctuaciones asincrónicas en el nivel del agua (34% fueron calificadas entre 4 y 5), y sedimentación (31% se calificaron de 4 a 5). Mediante un análisis factorial se identificaron cinco factores principales que explicaron la mayor parte de la variabilidad de las 14 medidas de degradación. Los factores incluyeron la sedimentación, hábitat estructural, eutroficación, régimen de aguas y plantas acuáticas. Tres factores de degradación estuvieron controlados mayormente por procesos sucedidos al interior de los reservorios mientras que los otros obedecieron a los influjos provenientes de los parte-aguas. En una comparación a lo largo de las regiones de EEUU, se encontró que existen diferencias geográficas significativas en cuanto a la degradación en función a factores particulares para cada región. Los reservorios se han considerado como innaturales y fuentes de perturbación, pero son producto de las políticas públicas, son un rasgo críticos del paisaje y, en caso que los manejadores pretendan conservar de manera efectiva los sistemas fluviales, no pueden ser ignorados. La protección y restauración de los hábitats en los reservorios pueden mejorarse con una perspectiva más amplia que contempla el manejo de cuencas y actividades realizadas al interior de estos cuerpos de agua.

It has been conjectured that reservoirs differ in the rate at which they manifest senescence, but no attempt has been made to find an indicator of senescence that performs better than chronological age. We assembled an indicator of functional age by creating a multimetric scale consisting of 10 metrics descriptive of reservoir environments that were expected to change directionally with reservoir senescence. In a sample of 1,022 U.S. reservoirs, chronological age was not correlated with functional age. Functional age was directly related to percentage of cultivated land in the catchment and inversely related to reservoir depth. Moreover, aspects of reservoir fishing quality and fish population characteristics were related to functional age. A multimetric scale to indicate reservoir functional age presents the possibility for management intervention from multiple angles. If a reservoir is functionally aging at an accelerated rate, action may be taken to remedy the conditions contributing most to functional age. Intervention to reduce scores of selected metrics in the scale can potentially reduce the rate of senescence and increase the life expectancy of the reservoir. This leads to the intriguing implication that steps can be taken to reduce functional age and actually make the reservoir grow younger. Se ha discutido que los reservorios se diferencian entre sí por la tasa a la cual manifiestan senescencia, sin embargo no ha habido esfuerzos para encontrar un indicador de senescencia que funcione mejor que la edad cronológica. Se construyó un indicador de edad funcional mediante una escala multimétrica que consiste en diez métricas descriptivas del ambiente de los reservorios que se previó que cambiaran de dirección a medida que aumenta la senescencia de los reservorios. En una muestra de 1,022 reservorios en los EE.UU., no se encontró correlación entre la edad cronológica y la edad funcional. La edad funcional estuvo directamente relacionada con el porcentaje de tierra cultivada y la capacidad de captación del reservorio, e inversamente relacionada con la profundidad de este. Más aún, algunos aspectos de la calidad para la pesca en el reservorio y características de las poblaciones de peces explotadas, también se relacionaron con la edad funcional. Una escala multimétrica como indicativo de la edad funcional de un reservorio presenta la posibilidad para intervenir en el manejo en varios frentes. Si un reservorio está envejeciendo en términos funcionales a una tasa acelerada, se pueden tomar acciones para remediar aquellas condiciones que más contribuyen con el envejecimiento funcional. La intervención dirigida a reducir las calificaciones sólo de métricas selectas puede potencialmente reducir la tasa de senescencia e incrementar la expectativa de vida del reservorio. Esto da pie a la curiosa implicación que es posible reducir la edad funcional de los reservorios y, de hecho, hacerlos más jóvenes.