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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of first feeding (Lasker 1975; Parrish et al. 1981; Theilacker 1986; Simpson 1987;

Theilacker 1987). Thus, environmental changes affecting distribution and abundance of

food are reflected in year-class strength.

Altered environments can add new bottlenecks but more often change timing

and/or magnitude of existing impacts (Minckley et al. 1991). Thus, identification oflife

stage{s) most sensitive to perturbations and factor{s) limiting that stage in nature are

critical to understanding how change is likely to affect a species (Kaeding and

Osmundson 1988). Environmental changes often have similar effect for species with

similar reproductive strategies (Berkman and Rabeni 1987).

Fish communities in seasonally variable habitats are often dominated by two kinds

of strategists, opportunists and seasonal (Winemiller 1989). The former tend to be short-

lived and small-bodied, such as many cyprinid fishes that may remain reproductive even

in periods of high potential adult and larval mortality (Reznick and Endler 1982). Here,

maturation rates are rapid and populations build rapidly following perturbations. An

ability to recolonize marginal habitats under unpredictable conditions is a major adaptive

feature (Minckley and Barber 1971; Winemiller 1989). Such fishes are most often

associated with smaller or headwater streams and less commonly with larger ones.

Alternatively, seasonal strategists tend to be large-bodied, long-lived, with cyclic

(seasonal) reproduction, relatively long generation time, large clutches, and small

investment in each offspring (Murphy 1968; Baltz 1984; Winemiller 1989). They tend to

occupy high-order streams, spawning at the onset of or during floods. Population

increases can be rapid, owing to the large influx of juveniles. The time required for larval

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