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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CHAPTER 3. ANALYSIS OF A RELATIVE CONDITION (KN) INDEX AND

PROXIMATE BODY COMPOSITION TO ASSESS NUTRITIONAL STATUS IN

LARV AL RAZORBACK

I. Introduction:

Events affecting mortality during the early life-history phases of many fishes are

important in determining their survival and its subsequent effect on population

recruitment dynamics (May 1974; Cushing 1975; Houde 1987; Rice et al. 1987).

Differences observed between groups of larvae sampled at various stages in their life-

history can provide information on how agents of mortality act, including whether they

are size or age-specific, or depend on timing of external environmental factors (Brown

1978; Rice et al. 1987). Growth patterns are thus an important indicator of environmental

conditions. Growth directly affects survival because fast-growing fishes are less

vulnerable to size-selective predation for shorter duration and may be in better condition

to overwinter or compete (Ware 1975; Fogarty et al. 1991; Thompson et al. 1991).

Growth in fishes is related to the environment through temperature and food availability,

habitat quality, and water quality, and represents the last repository for energy after

demands of metabolism and activity are met (Brett and Groves 1979; Ney 1993; Diana

1995). Thus, determining differences in growth patterns among and within populations

provides a generalized picture as to how fishes are responding to their environment.

The difficulty associated with growth is how to measure and interpret it in a

meaningful way. Length, mass, and proximate measures of body composition such as

lipids, are generally used to describe growth. However, each may individually prove only

of limited usefulness. Body length is readily measured, but two fish of the same length