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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ABSTRACT
An increasing tendency toward alteration and destruction of natural habitats has

accompanied the growth of human demands upon the global environment. There are few

rivers world-wide where one to many indigenous species are not imperiled due to changes

in ecosystem characteristics. Aquatic habitats of arid western America have suffered in

particular, and freshwater fishes ill-adapted at some stage of their life-history to cope with

such changes have decreased precipitously in abundance. Identification of life-stages

most sensitive to environmental pressures may reveal why these species are disappearing.

Among factors regulating populations, nutrition and predation upon larvae have been

identified as major bottlenecks to recruitment among large river fishes identified as

seasonal strategists. Of these fishes, the razorback sucker appears especially constrained

by lack of recruitment through the larval stage. Major changes in ecosystem structure and

function have altered the patterns of productivity and floral and faunal characteristics in

the Colorado River system where the razorback lives. As such this study tested the

hypothesis that nutritional limitation on larval razorbacks is acting as an primary limiting

factor to recruitment in this species. Identification of the effect of different feeding

regimes on larval razorbacks was tested and developed in the laboratory using analyses of

age-structure, growth, lipids, morphology, and histology. Nutritional classification

criteria obtained were then applied to a series of larvae obtained from Lake Mohave and

an adjacent, highly productive backwater, Yuma Cove. As predicted for larvae in Lake

Mohave there is evidence that nutrition does playa potentially important role in limiting

recruitment in this species. There was substantial seasonal and spatial variability in

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