8136

• UCREFRP Catalog Number: 8136
• Author: Bestgen, K. R.
• Title: Growth, survival, and starvation resistance of Colorado squawfish larvae.
• USFW Year: 1995.
• USFW - Doc Type: \
• Copyright Material: YES

202

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260C
/j; 300C
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100 150 200 250
Ration (nauplii fish'l d.1 )

350

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300

Fig, 2. Main and interaction treatment effects on mean growth of Colorado squawfish larvae in water temperatures of 18,22,26, and 300 C
and food abundance levels of 12.5,28,63,142, and 320 nauplii fish-I day-I, Mean (SE) growth for each treatment combination and the
response surface model coefficients are in Tables 1 and 2,

1988). The interaction here is orderly because
growth at higher food rations at 180 C is always less
than other temperatures, so straightforward inter-
pretation of main effects is appropriate.

Survival response

Survival of Colorado squawfish larvae was not sig-

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Ration (nauplii fish' d-')

Fig, 3, Response surface of surVival of Colorado squawfish larvae
in replicated treatments as a function of water temperature and
food abundance (In scale). Mean (SE) survival for each treatment
combination and the response surface model coefficients (as logit
(S)) are in Tables 1 and 2; the star represents the optimal survival
response as a function on the independent variables,

nificantly different in constant and fluctuating re-
gimes (p = 0.67), and QAIC did not select models
with regime or any of its interaction terms included,
so data for the same temperatures were pooled in
subsequent analyses. Response surface analysis
and QAIC indicated survival of Colorado squaw-
fish larvae was best predicted by a model that in-
cluded food abundance (In transformed), temper-
ature, squared terms, and the interaction (Fig. 3).
Use of In transformed food abundance was justified
by improved survival model fit over that given by
untransformed values. Ln food abundance x tem-
perature interaction was the most important expla-
natory variable as determined by a stepwise regres-
sion selection procedure, followed by In food abun-
dance and its squared term, temperature squared,
and temperature (Table 2). The response surface
and model solutions indicated survival> 90% when
temperature ranged from 20 to 300 C and when
food abundance was> 180 nauplii fish-1 day-I. Ac-
tual survival values were about 90% or higher at ex-
perimental food abundances of 142 and 320 nauplii
fish-I day-I at temperatures of 22, 26 and 300 C (Ta-
ble 1). Survival was slightly reduced at 180 C, the
lowest temperature tested, even in the presence of
high food abundance and was lowest overall when
food abundance was low and temperature was high.