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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OVERVIEW
The objective of this research was to test the hypothesis that nutritional deficiency exists

among early life stage razorback sucker larvae (Xyrauchen texanus). If found can

nutritional deficiency explain the continuing demise of this species? Chapter 1 provides

brief synopse of life-histories of fish in seasonal environments and the importance to

studies in large river basins. This chapter provides a historical background of the

Colorado River system and the changes occurring to bring it to its present form. This

chapter introduces the razorback sucker, the general methodology and the approach used

in this study. Chapters 2-5 cover suitability of several techniques used to assess larval

fish populations to the razorback sucker. Relative condition and landmark analysis

represent novel approaches to the analysis of condition in larval fishes. Chapter 6 applies

the techniques developed in Chapters 2-5 to wild-caught larval razorback suckers

collected from Lake Mohave during 1992-1995, and from the adjacent Yuma Cove

backwater and discusses results and relative merits of each application. The chapter also

discusses potential ecological ramifications of reservoir and river management for this

species. Like Chapter 1, many of the analogies drawn for effects of river modifications

on this species are comparative in nature and based on results from other species, as

larvae for this study could only be obtained for a reservoir environment. It has only been

in the last two years (after this research was completed) that numbers of larvae to support

such investigations have been captured from riverine sections (all in the upper basin).

There are no captures of significant numbers of larvae elsewhere within the species'

current range.

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