Changes in fish communities of the Shoalhaven River 20 years after construction of Tallowa Dam, Australia

Abstract

This study was undertaken as part of a long-term investigation of the ability of high-level fishways to rehabilitate fish communities upstream of high dams. Effects of Tallowa Dam on fish of the Shoalhaven River system were studied by comparing species abundances, population size-structures and the structure of fish communities above and below the dam. Fish were sampled twice yearly for two years at 12 sites throughout the catchment. Species richness was greater downstream of the dam, with 21 species, compared to 16 species upstream of the dam. Ten diadromous species are believed to be extinct above the dam because of obstructed fish passage. Another four migratory species capable of climbing the wall have reduced abundances upstream. Accumulations of fish, particularly juveniles, directly below the dam were evident for nine species. Fish communities upstream and downstream of the dam differed significantly, identifying the dam as a significant discontinuity in the available fish habitats within the system. Historical evidence suggests that before the dam was built, fish communities from the tidal limit to at least 130 m elevation were largely continuous. This study has demonstrated that Tallowa Dam is a major barrier to fish migration and has had adverse effects on the biodiversity of the system. The creation of Lake Yarrunga by Tallowa Dam has resulted in distinctive fish communities in riverine and lacustrine habitats. Populations of five species that occur both upstream and downstream of the dam have developed differences in their size structures. The fish community downstream of the dam also differs from its historical condition because of the virtual disappearance of Australian grayling (Prototroctes maraena) and the establishment of non-native species.A high-level fishway is now being designed for the dam to restore fish passage. Data from this study will serve as a baseline against which to assess the effectiveness of the fishway in rehabilitating fish communities of the river system.

Distribution patterns of fish communities with respect to environmental gradients in Korean streams

“…Although the importance of conservation is widely acknowledged, development almost always takes priority (Balmford et al, 2002). Changes in fish communities caused by construction projects have been widely reported (Martinez et al, 1994;Gehrke et al, 2002;Habit et al, 2007).…”

Spatial variations in fish assemblage structure in a southeastern Brazilian reservoir

“…The fish assemblages present in reservoirs are a result of the restructuring of those assemblages that occupied the river segment before damming (Araújo-Lima et al, 1995). This process is marked by the extirpation of some species, reduced abundances of many species (Gehrke and Harris, 2001;Gomes and Miranda, 2001;Gehrke et al, 2002), and proliferation of other species (Pelicice and Agostinho, 2009). It is expected that species with greater plasticity in their feeding and spawning requirements are among the dominant ones (Gehrke and Harris, 2001).…”

“…This process is marked by the extirpation of some species, reduced abundances of many species (Gehrke and Harris, 2001;Gomes and Miranda, 2001;Gehrke et al, 2002), and proliferation of other species (Pelicice and Agostinho, 2009). It is expected that species with greater plasticity in their feeding and spawning requirements are among the dominant ones (Gehrke and Harris, 2001). Population depletions occur mainly among species that are migratory, long-lived, and have low reproductive potential (Agostinho and Gomes, 2006).…”

Ecological assessment of a southeastern Brazil reservoir

“…Physical habitat modifications directly influence the composition and structure of aquatic communities (Kaufmann et al 2014), and alter organism diets, reproduction, and growth (Benedito-Cecílio et al 1997). As a result of all these influences, and because of the dam itself, aquatic communities undergo changes (Gehrke et al 2002, Agostinho et al 2008) that favor biological invasion (Rocha et al 2011).…”