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 2. EV ALUA nON OF OTOLITHS FOR AGING LARVAL RAZORBACK

SUCKERS

I. Introduction:

Defining environmental variables affecting recruitrilent is a central problem in

fisheries (Lasker 1987). Year-class strength is often determined within the first few

weeks of life, thus differences in hatching dates, size-selective mortalities, and spatial

differences in survival may provide information regarding mechanisms affecting

recruitment success (Houde 1987). Age-structure analysis provides an accurate record of

temporal and spatial differences in mortality in fish populations (Methot 19,83; Rice et al.

1985, Houde 1987).

Scales, opercular bones, spines, rays, and otoliths have been used to accurately

age individual fish (Campana and Neilson 1985). Age analysis was, however, carried a

step further when Panella (1971, 1974) described otolith depositional layers in young-of-

the-year fishes occurring with 24-hour periodicity, thus offering a previously unavailable

means of studying this life-history stage.

Three pairs of otoliths (asterisci, lapilli, and saggittae) are present in the inner ear

of teleost fish, where they serve a sensory function. Otoliths are much denser than the

surrounding body, which is essentially acoustically transparent, and consequently they

move out of phase with the sensory epithelia (popper and Platt 1993). Otoliths are

stimulated directly through vibrations, or indirectly via Weberian ossicles when present,

which acoustically couple the gas-bladder to the inner ear. Otolith size generally reflects

fish size closely. Their conservative growth relative to other structures such as scales

suggest they configure precisely to the rest of the fish's otic system (Campana and