8142

• UCREFRP Catalog Number: 8142
• Author: Horn, M. J.
• Title: Nutritional Limitation of Recruitment in the Razorback Sucker ‎(
• USFW Year: 1996.
• Copyright Material: NO

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13

reservoirs are changed from seasonally variable to predetermined limits, with substantial

fluctuations dictated by daily, weekly, seasonal or other water and power demands, thus

limiting availability and productivity of fringing habitats (Figure 2b) (Cushman 1985;
Weisberg et al. 1990; Stanford 1994; Blinn et al. 1995).

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Introduced Fishes
Introduced fishes, such as common carp (Cyprinus carpio) and catfishes [bullhead

(Ameiurus) sp., and perhaps channel catfish (Ietalurus punctatus)] were locally common

near Yuma, Arizona, by 1900 (Minckley 1973). Dill (1944) reported these and several

additional alien species, while Minckley (1979) found 29. The river also has experienced

similar increases in non-indigenous species of aquatic plants, molluscs, crustaceans, and

other groups (USFWS 1981). In this, and almost all examples of river modification shifts

in species and abundances have occurred.

Appearances of these organisms mostly resulted from intentional stocking by

humans for their potential or actual values as food (Le., common carp, some catfishes),

sport [trouts, flathead catfish (Pylodictis olivaris) channel catfish, centrarchids,
percichthyids], forage for sport fishes [red shiner (Cyprinella lutrensis), threadfin shad
(Dorosoma petenense) or agents of biological control [western mosquitofish, (Gambusia
affinis), African cichlids (Tilapia zilli) and (Sarotherodon spp.), grass carp
(Ctenopharyngodon idellus)]. Accidental introductions of bait fishes, crayfish
(Astacidae) and aquarium fishes [e.g., sailfin molly (Poecilia latipinna)] also contributed
to this artificial biota. Most aliens that became naturalized were lentic adapted, with