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Large River Fish
• ~ 10,000 species
• > 2,000 species in Amazon (not all unique)
• Ancient freshwater fishes are river fishes
Factors Influencing Distribution/Diversity
• Current Velocity
• Substrate
• Refugia
• Habitat– “normal”– Spawning– Seasonal
• Biodiversity
Raibley et al. (1997)
• Winter habitats used by largemouth bass in the Illinois River. N. Amer. J. Fish. Mgmt.
• Radio-tagged fish in Illinois River
• Tracked through different seasons and electroshocked
Most winter sites are man-made. Why?
Wintering Sites
• Current velocities lower– Winter site 2 cm/sec– Channel 19 cm/sec
• Temperatures higher– Springs– Industrial outflows
• Dissolved oxygen remains high
Most winter sites are man-made. Why?
Boys and Thoms (2006)
• A large-scale hierarchical approach for assessing habitat associations in large dryland rivers. Hydrobiologia
• Effects of scale on distribution and diversity of fishes
Zone 1 very different Zones 2 and 3, not zone 4fewer fish, higher abundance native species
Zone 2 distinct from all other zonesfewer native fish, more non-native species
Zone 3 very different Zones 1 and 2, not zone 4High abundance of some natives and carp
Zone 4 fish composition highly variable; greatest species richness of all zones
Valdez et al. (2001)
• Effects of a test flood on fishes of the Colorado River in Grand Canyon, Arizona. Ecological Applications 11:686-700.
• Extensive loss of beach and slackwater habitats since dam construction
• Managed flood used to rebuild these patches
• Examined response of fish
Figure 2
Why no difference infish abundance beforeand after flood?
BUT, What about other aspects of hydrology?
• Five aspects of river flow (Poff et al. 1997)
• Colorado River – predictable flood pulse, relatively low intraannual variability
• Plains rivers – greater hydrological variability
Adams et al. (2004)
• Spatial and temporal patterns in fish assemblages of upper coastal plain streams, Missississippi, USA. Hydrobiologia 528:45-61.
• Examined fish assemblages in a hydrologically variable river
Community dominated by “colonizingassemblages” – r-selected taxa
Same Pattern for Plains Rivers (Kansas R.)
• Dominant taxa– Small Cyprinidae (Notropis, Cyprinella,
Macrhybopsis, Hybognathus)– Fundulus– Other small-bodied, short-lived taxa
• Rare taxa– Piscivores– Large omnivores (e.g., Ictiobus)