7760

• UCREFRP Catalog Number: 7760
• Author: Beyers, D. W., R. T. Muth and M. S. Farmer.
• Title: Experimental Evidence of Competition Between Larvae of Colorado Squawfish and Fathead Minnow.
• USFW Year: 1994.
• USFW - Doc Type: \
• Copyright Material: NO

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Materials and Methods
Experimental animals
Colorado squawfish were obtained from Dexter National Fish Hatchery and
Technology Center, Dexter, New Mexico. Fathead minnow larvae were purchased
from a commercial source (Aquatic Biosystems, Inc., Fort Collins, Colorado).
After onset of first feeding, all larvae were fed live 24-h-old brine shrimp
nauplii (Aquarium Products, Glen Burnie, Maryland) twice daily.
To ensure that larval Colorado squawfish and fathead minnow were capable
of eating the same prey, the experiment was initiated when both species first
began to consume brine shrimp nauplii. This was accomplished by purchasing
fathead minnow that were expected to reach the developmental phase at
approximately the same time as Colorado squawfish. Thus, the decision of when
to start the experiment was based on functional development of foraging
abilities instead of correlated measures such as body length or mouth gape.
Mean wet mass and total length at start of the experiment were 4.16 mg and
8.4 mm for Colorado squawfish 'and 2.23 mg and 7.0 mm for fathead minnow.
Initial mass and length were determined by measuring 20 fish sacrificed and
preserved at the start of the experiment.
Experimental design and conditions
The duration of the experiment was 14 d. Experimental treatments were
assigned to replicate aquaria using a completely randomized, 3X5 factorial
design. The first factor, feeding regime, had three levels (32, 80, and
200 zooplankton•fish-~•day~~). The second factor, relative abundance, had five
levels (ratios) of % Colorado squawfish:q° fathead minnow (100:0, 75:25, 50:50,
25:75, and 0:100). Each treatment was replicated three times and the
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