8021

• 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: YES

110

BESTGEN AND BUNDY

TABLE 4.-Least-squares statistics for regression of lapillus diameter (LD, fLm) as a function of loge (total length,
nun) of Colorado squawfish incubated and reared for 165 d with constant temperatures (220C) or with diel temperature
fluctuations centered on 18, 22, or 260C, Regressions are LD = a + b.loge (total length). Fish less than 2 d old were
excluded from this analysis because their otolith and length measurement residuals were positively biased.

Intercept: Slope:
Treatment df a (SE) b (SE) r2
\8'e fluctuating 45 -\98,\1 (5,47) \06.73 (2,13) 0,983
22'e fluctuating 4\ - 220.20 (6,97) \16,75 (2,60) 0.98\
22'C constant 40 -227,81 (4.62) 120,43 (1.76) 0,992
26'e fluctuating 51 -22237 (5.56) \18,43 (2,14) 0,984
All treatments
combined \80 -2]6.72 (3,\2) \15,49 (1.\9) 0,98\

Somatic Growth versus Otolith Growth

Three experiments were conducted to determine
the effects of slow and fast somatic growth rate
(experiment 1) and different starvation periods
(experiments 2, 3) on otolith growth patterns.
When analyzed by ANCOV A, squared values for
dependent variables resulted in better fits than loge
transformations. Also r2 values for linear equa-
tions with squared dependent variables were as
high as or higher than those achieved by nonlinear
regressions.
For experiment 1 (growth rates), ANCOV As in-
dicated significant differences in regression slopes
between treatments whether dependent variables
were squared or log-transformed. This experiment

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showed that otoliths of slower-growing fish were
larger than otoliths of faster-growing fish of the
same length (Figure 1). Fitted equations show, for
example, that lapillus diameter of a 25-mm fish
was 18% larger in the slow-growth treatment than
in the fast-growth treatment. Such an outcome re-
sulted from differential treatment effects on so-
matic and lapillar growth. A 60-d-old fish in the
slow-growth treatment averaged 56% smaller than
the same-aged fish in the fast-growth treatment
(Figure 2), but its lapilli averaged only 33% small-
er (Figure 3).
In experiment 2, wherein food was withheld
from fish for 6 d between two 6-d feeding periods,
somatic growth of starved fish ceased whether

o

o

10 20 30 40 50
Colorado squawfish TL (mm)

60

FIGURE l,-Regressions of squared lapillus diameter (LD, /Lm) as a function of Colorado squawfish total length
(TL) for fish in slow- and fast-growth treatments, For the slow-growth treatment, LD2 = -135,742.1 + 15,658(TL);
r2 = 0,97; N = 40; SE of intercept = 11,293; SE of slope = 485. For the fast-growth treatment, LD2 = -133,328.4
+ 13,984,9(TL); y2 = 0,97; N = 24; SE of intercept = 13,847; SE of slope = 490.