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UCREFRP
UCREFRP Catalog Number
8021
Author
Bestgen, K. R. and J. M. Bundy
Title
Environmental Factors Affect Daily Increment Deposition and Otolith Growth in Young Colorado Squawfish
USFW Year
1998
USFW - Doc Type
Transactions of the American Fisheries Society
Copyright Material
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<br />\~q~ ~t~~~~~() <br /> <br />Transactions of the American Fisheries Society 127:105-117, 1998 <br />@ Copyright by the American Fisheries Society 1998 <br /> <br />1{Dd.\ <br /> <br />Environmental Factors Affect Daily Increment Deposition and <br />Otolith Growth in Young Colorado Squawfish <br /> <br />. <br /> <br />KEVIN R. BESTGEN1 AND JAY M. BUNDY <br /> <br />Larval Fish Laboratory, Department of Fishery and Wildlife Biology <br />Colorado State University, Fort Collins, Colorado 80523, USA <br /> <br />Abstract.-Otolith microstructure of endangered Colorado squawfish Ptychocheilus lucius was <br />investigated to determine patterns of otolith growth and to validate daily deposition of increments. <br />Sagittae and lapilli formed prior to hatching. After fish hatched, otolith increments were deposited <br />daily whether larvae were reared at a constant 220C temperature or subjected to fluctuating tem- <br />peratures (:t2.50/d) centered at 18, 22, or 26"C. Otolith increments were clearer and counts of <br />increments were more accurate for fish reared at fluctuating than at constant temperatures. Otolith <br />growth was lower at 180C than at 22 or 260C, but evidence of a direct effect of temperature on <br />otolith growth was inconclusive, Lapillus diameters of slow-growing Colorado squawfish were <br />larger than those of similar-sized but fast-growing fish, indicating that fish and otolith growth rates <br />were not proportional. When larvae were starved, growth in body length generally ceased im- <br />mediately but otolith growth continued for up to 15 d, Otolith growth was reduced for up to 5 d <br />after starved fish began to feed. Timing of starvation and reduced growth may not be accurately <br />recorded by reduced otolith increment spacing. Low-contrast otolith increments in wild fish may <br />illdicate periods of low food abundance and starvation, Increased otolith growth early in life could <br />reflect the start of exogenous feeding by Colorado squawfish larvae, a habitat ~hift to warmer <br />water, or both, Otolith analysis will be useful for elucidating age, growth, and recruitment patterns <br />of young Colorado squawfish, <br /> <br />t, <br /> <br />Numbers of daily increments in fish otoliths, <br />patterns of increment deposition, and otolith <br />growth rates may record life history events such <br />as hatching, growth stanzas, periods of physiolog- <br />ical stress, movements, and changes in water tem- <br />perature or food abundance (Methot 1983; Cam- <br />pana and Neilson 1985; Penney and Evans 1985; <br />Rice et aI. 1985; Eckmann and Rey 1987). Cor- <br />relation of biological data from otoliths with en- <br />vironml~ntal factors such as water temperature, riv- <br />er discharge, food availability, and predator abun- <br />dance bas elucidated mechanisms that control <br />growth. survival, and recruitment of early life <br />stages of fish (Crecco and Savoy 1985; Houde <br />1987; Rice et aI. 1987). <br />Uses of otolith data in biological investigations <br />accelerated after Pannella (1971) discovered daily <br />otolith growth increments. Subsequent research in- <br />dicated that increment formation and otolith <br />growth rates are influenced by photoperiod, water <br />temperature, diel water te~ature fluctuations, <br />food abundance, somatic growth rate, and meta- <br />bolic rates (Taubert and C6ble 1977; Campana and <br />NeiIsOCl1985; Secor and Dean 1989, 1992). More- <br />over, rhythmic environmental events such as pho- <br />toperiod and diel temperature shifts may entrain <br /> <br />~ <br /> <br />1 Corresponding author: <br />kbestgen@picea.cnr.colostate.edu <br /> <br />an endogenous endocrine-driven circadian rhythm <br />that controls daily increment deposition and otolith <br />growth (Campana and Neilson 1985; Secor and <br />Dean 1992). Although otolith growth and somatic <br />growth (used in this paper to mean increase in body <br />length) generally are positively correlated (Cam- <br />pana and Neilson 1985), the assumption of closely <br />proportional growth may be flawed because otolith <br />growth sometimes is consistent during periods of <br />variable somatic growth (Mosegaard et aI. 1988; <br />Reznick et al. 1989; Secor and Dean 1989; Wright <br />et al. 1990; Francis et aI. 1993). This "growth rate <br />effect" may invalidate some back-calculations of <br />fish length based on proportional otolith and so- <br />matic growth (Campana 1990). Species-specific <br />validation of increment deposition and otolith <br />growth patterns-defined by Francis (1995) as es- <br />timating the accuracy of determination methods- <br />is critical because of the many factors that affect <br />otolith microstructure. <br />Here, we report on effects of environmental con- <br />ditions on daily increment formation and otolith <br />growth in young Colorado squawfish Ptychochei- <br />Ius lucius, an endangered cyprinid endemic to the <br />Colorado River basin (Behnke and Benson 1983; <br />Tyus 1991). To determine if otoliths can be used <br />to describe age and growth of early life stages of <br />Colorado squawfish in the wild, we tested the fol- <br />lowing hypotheses: (1) increment deposition be- <br /> <br />105 <br />
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