Habitat utilisation by fish community in a short-term regulated river reservoir

The population dynamics and behavior of an assemblage of fishes in a small bog lake were studied in a succession of whole-lake manipulations of piscivores. Total prey fish biomass declined after the addition of northern pike (Esox lucius). This decline was the result of emigration by cyprinid prey and consumption by northern pike. The emigration response of the cyprinids was dependent on cyprinid density. At high prey fish biomass, a significant portion of the loss in biomass was the result of emigration; this was not the case at low prey fish biomass. The prey fish community shifted from small-bodied soft-rayed species prior to the introduction of northern pike to species with spines or deep bodies after predator stocking. The community response was analyzed at four levels of numerical resolution: absolute, relative, and ranked abundance and presence–absence of prey species. High numerical resolution captured the dynamic short-term population responses to predation and suggests unstable community structure.

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Response of a floodplain fish community to river-floodplain connectivity: natural versus managed reconnection

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2013-0042 ◽

2014 ◽

Vol 71 (2) ◽

pp. 236-245 ◽

Cited By ~ 21

Author(s):

R.J. Stoffels ◽

K.R. Clarke ◽

R.A. Rehwinkel ◽

B.J. McCarthy

Keyword(s):

Native Species ◽

Fish Community ◽

Large Scale ◽

Environmental Flows ◽

Regulated River ◽

Pest Species ◽

Fish Community Structure ◽

River Floodplain ◽

Natural Connection ◽

Flood Pulses

To restore lateral connectivity in highly regulated river-floodplain systems, it has become necessary to implement localized, “managed” connection flows, made possible using floodplain irrigation infrastructure. These managed flows contrast with “natural”, large-scale, overbank flood pulses. We compared the effects of a managed and a natural connection event on (i) the composition of the large-bodied fish community and (ii) the structure of an endangered catfish population of a large floodplain lake. The change in community composition following the managed connection was not greater than that exhibited between seasons or years during disconnection. By contrast, the change in fish community structure following the natural connection was much larger than that attributed to background, within- and between-year variability during disconnection. Catfish population structure only changed significantly following the natural flood. While the natural flood increased various population rates of native fishes, it also increased those of non-native carp, a pest species. To have a positive influence on native biodiversity, environmental flows may need to be delivered to floodplains in a way that simulates the properties of natural flood pulses. A challenge, however, will be managing river-floodplain connectivity to benefit native more than non-native species.

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