7016

• UCREFRP Catalog Number: 7016
• Author: Larval Fishes Laboratory.
• Title: Development of Marking and Otolith-ageing Techniques for Colorado Squawfish
• USFW Year: 1986.
• USFW - Doc Type: Report on Study-Phase 1.
• Copyright Material: NO

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-All lot.- in both tests were incubated in a _
water bath. Fish were not fed during experiment.
-Experiments were terminated 10 days after start
of treatment for egg test and 3 days after start
of treatment for larva test; otoliths were
removed and examined with U-V light microscope.
--Experiment 2
-Larvae, 2 days post
mg/l TC solution of
About 3,000 marked
plastic tank, fed
and reared for more
hatching, were immersed in 100
freshwater for 7 hr at 20C.
larvae were keLt in 500 ml
rotifers and commercial food.
than 5 months.
-About 15 times during the experiment, 50-100 fish
were sampled and otoliths removed and examined in
same manner as in Experiment 1.
--Experiment
-Same ,procedures as in Experiment 2 plus 3,000
control fish.
-monitored survival and changes in body length of
both groups.
-Results
--Experiment '1_
-200-300 mg/l for 24-48 hr optimal for eggs;
200-300 mg/l for 3-24 hr optimal for larvae.
--Experiment 2
-Marked easily detectable (100%) for 105 days post
hatching without any special preparation of
otoliths. Even 164 days after hatching the
percent retention was 100% after grinding or,
etching of otoliths.
--Experiment 3
-Treatment had no effect on survival and growth of
larvae.
-Conclusions
--Method can be applied to field surveys on the ayu.
--Merits of method: (1) suitable for eggs and newly
hatched larvae, (2) rapid mass-marking with 100%
initial success can be achieved, (3) retention time
is comparatively long, (4) no effect on fish's
growth or mortality.

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