Fish Habitat Degradation in U.S. Reservoirs

• Published in: Fisheries 2010-04, Vol.35 (4), p.175-184
• Main Authors: Miranda, L. E., Spickard, M., Dunn, T., Webb, K. M., Aycock, J. N., Hunt, K.
• Format: Article
• Language: English
• Subjects: Aquatic plants; Environmental degradation; Environmental protection; Environmental restoration; Eutrophication; Factor analysis; Fish; Freshwater; Habitats; Land degradation; Macrophytes; Public policy; Reservoirs; River systems; Siltation; Surveying; Water level fluctuations; Water levels; Watershed management
• ISSN: 0363-2415; 1548-8446; 1548-8675
• DOI: 10.1577/1548-8446-35.4.175

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