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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38

Under normal circumstances, feeding regimen is not thought to influence daily

increments (Reznick et al. 1989). Food deprivation only has an effect after energy

reserves are exhausted, as in starving fish (Secor and Dean 1982). Temperature

significantly reduces deposition rates when low enough to curtail growth (Taubert and

Coble 1977; Neilson and Geen 1982; Radke and Dean 1982) and formation of more-than-

single increments per day have been noted at high environmental temperatures (Eckman

and Rey 1989). The primary influence of photopeiod is to entrain the daily cycle of

increment formation (Tanaka et al. 1981). Due to these uncertainties, and depending on

goals of a study, species-specific validation is advisable.

Accordingly, my goal was to validate daily otolith increments for larval razorback

suckers. This, along with impacts of starvation on otolith formation and growth relative

to somatic growth, were studied in the laboratory.

ll. Methods:

Analyses of otoliths in laboratory larvae were performed to determine: 1) timing

of initial increment formation; 2) frequency of increment deposition; 3) if increment

formation was dependent on growth; and 4) if otolith growth was proportional to somatic

growth. Larvae were placed on Starved, Suboptimal, and Ad libitum rations and

periodically sacrificed for analysis.
Eggs for the Suboptimal feeding level were from fish spawned March 9. Otoliths
were examined for Starved and Ad libitum larvae spawned March 15. For each