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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37

Neilson 1985). Daily otolith growth increments form via differential deposition of

calcium carbonate and protein, and appear as a bipartate structure consisting of light and

dark banding. The light banding (incremental zone) is largely calcium carbonate

deposited as aragonite, and appears to be a under endochronological control. The dark

zone is a matrix of the protein otolin, but little is understood of the cycle of its formation.

Under most circumstances otolioths provide a more accurate record of growth than do

other structures, because of the diel and conservative nature of increment formation

(Campana and Neilson 1985).

The accuracy with which aging can be done is based on two assumptions con-

cerning otoliths themselves: 1) features are produced consistently and at a constant

periodic rate (daily, yearly); and 2) distances between features (e.g., otolith increment) are

proportional to growth of other body parts (panella 1974). Consistency of daily otolith

increments appear to fit the first assumption well for many species, more so than for

annual increments marked by annuli (Campana and Neilson 1985; Jones 1986). The

second assumption is, however, less reliable.

Relationships between otolith and somatic growth are influenced by numerous

factors (Rice et al. 1985; Geffen 1992). Generally, time of formation varies among

species, and periodic growth increments are mediated by an endogenous, endocrine-

driven circadian rhythm (Taubert and Coble 1977; Campana and Neilson 1982).

Periodicity of increments, however, may by influenced by feeding regimen, temperature,

and photoperiod.