Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: May 01, 2000

Temperature Effects of Hypolimnial-Release Dams on Early Life Stages of Colorado River Basin Big-River Fishes

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Page Range: 402 – 412
DOI: 10.1643/0045-8511(2000)000[0402:TEOHRD]2.0.CO;2
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Abstract

Declines of native big-river fishes of the Colorado River Basin, southwestern United States, have been attributed in part to emplacement of hypolimnial-release dams. Lowered spring-summer tailwater temperatures inhibit spawning and embryonic development, depress swimming performance and growth, and reduce survival of early life stages. We examined effects of three temperatures (10 C, 14 C, 20 C) on aspects of growth, development, and physiology of larval and early juvenile life stages of Xyrauchen texanus (Razorback Sucker), Catostomus latipinnis (Flannelmouth Sucker), Gila cypha (Humpback Chub), and Ptychocheilus lucius (Colorado Squawfish) in the laboratory. Lengths, weights, and specific growth rates of all species were significantly lower at 10 C and 14 C than at 20 C, and time to transformation from larval to juvenile life stage was delayed at colder temperatures. Transfer of fishes from 20 C to 10 C (simulating transport from warm tributaries to cold tailwaters) caused loss of equilibrium in youngest life stages. All these effects increase exposure of larvae to existing sources of mortality. Conservation of the big-river species in hypolimnial-release tailwaters will require thermal modification of dam discharges to lessen detrimental effects of cold water temperatures. Because such action may also benefit nonindigenous biota, recovery of the native fauna may ultimately depend upon implementation of comprehensive (and likely expensive) control measures against nonnative species.

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Copyright: The American Society of Ichthyologists and Herpetologists
Fig. 1.
Fig. 1.

Changes in length (TL) over time of early life stage big-river fishes reared at three temperatures. Points represent mean responses of each species; ages are days posthatch at initiation of experiment. Circles denote 10 C, squares 14 C, and triangles 20 C


Fig. 2.
Fig. 2.

Changes in weight over time of early life stage big-river fishes reared at three temperatures. Points represent mean responses of each species; ages are days posthatch at initiation of experiment. Circles denote 10 C, squares 14 C, and triangles 20 C. Note the y-axis scale breaks for age-7 and age-14 Gila cypha


Fig. 3.
Fig. 3.

Mean specific growth rate (SGR) of early life stage big-river fishes reared at three temperatures. Ages are days posthatch at initiation of experiment. Circles denote 10 C, squares 14 C, and triangles 20 C


Accepted: Sep 24, 1999