8061

• UCREFRP Catalog Number: 8061
• Author: Mueller, G. and P. Marsh.
• Title: Post-Stocking Dispersal, Habitat Use, and Behavioral Acclimation of Juvenile Razorback Suckers ‎(
• USFW Year: 1998.
• Copyright Material: NO

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inside sago pond weed beds or behind dense stands of submerged tamarisk, detection range was
reduced to <40 m. Unfortunately, as spring run-off increased, rising reservoir elevations flooded
broad (>200 m) bands of tamarisk. Tests proved submergent vegetation not only interfered with
signal reception, but also proved impenetrable to watercraft. We were unable to effectively
survey hundreds of hectares of flooded habitat near Owls Point and Wagon Wheel Cove (Lake
Mohave) or at Piute Farms (Lake Powell).

Equipment failure is always a consideration when contact is lost with a fish. Initial failure rate
was 2.5% (2 of 80). It is impossible to determine transmitter failure after fish were released,
however, based on the longevity ofthe stationary transmitters, we believe failure was low.
While we acknowledge that we could not be 100% effective on each survey, we feel that any fish
that remained active, in either of the survey areas would have been eventually detected. The only
other explanations for losses are: 1) equipment failure, 2) the removal offish and transmitter
from the system by terrestrial or avian predator, or 3) fish found, penetrated, and remained in the
large, impenetrable flooded habitats where they were undetectable by telemetry equipment.

Tank Tests

We conducted tank tests on 2 groups of juvenile suckers to determine the shedding rate of
externally attached transmitters and the healing process. Transmitters were attached with a
single suture to the dorsal keel ofa group offive fish (5<23 crn/2I-27 cm). Fish were held in a
holding tank ( 2 m diameter X 1 m deep) for 8 weeks. Fish were fed daily and examined weekly.
The sutures gradually worked through the dorsal tissue. The wounds appeared clean, no bacterial
or fungal infections were noticed. Average transmitter retention was 3.8 weeks (2->.8 weeks)
and all fish recovered. Suture wounds healed within 2-4 weeks.

Similar tests were conducted with ten larger fish (5<=29 crn/27-32 cm) using two sutures. A
control fish (no transmitter) was also placed in the tanle Five fish, including the control, died of
unknown causes. Sutures of the study fish did not appear inflamed or infected. The first
transmitter was lost on week 5 and the remaining 5 fish retained their tags through week 9.

DISCUSSION

Stocking Dispersal

Individual movements and ranges are quite variable. It appears roughly 50% of stocked suckers
emigrate out of the 46 krn study area during the first month. These movements are similar to
those reported for juvenile flannelmouth suckers by Chart and Bergensen (1992). They reported
that juvenile flannelmouths moved more, and had ranges larger than sexually active adults.
Results were similar to comparisons made between the home ranges of adults and the movements
of a single juvenile razorback sucker in Lake Mohave (Mueller et ale 1998).

Other than knowing that dispersal is wide spread, the actual range continues to be unknown.