| To
better understand fish use of Delta Marsh, during
2000, 10 walleye were implanted with miniature radio
transmitters. In 1999, 22 walleye and six carp were
implanted. Fish entering the marsh at Clandeboye
Channel and within the marsh at Waterhen Creek were
caught in gill nets. Fish that were large enough
for implantation were anesthetized and a transmitter
was surgically implanted into their abdominal cavity.
Transmitters measure 11 x 59 mm and weigh 10.3 g.
Minimum expected life of the batteries is 163 days.
Fig. 4- Clandeboye Channel
Fig. 5- The gill net
Fish surgery
Mobile
Tracking
Once the fish were implanted
with the transmitters, they were released into
Clandeboye Bay and Waterhen Creek. Fish locations
within the marsh are determined using a mobile
boat-mounted antenna and receiver. Each day,
field staff move from bay to bay within the
marsh and scan for radio signals from the transmitters.
Each radio transmitter has a unique frequency
which permits us to identify individual fish.
Once a signal has been detected, the crew will
narrow down the location of the signal. When
a site has been determined for a fish, a Global
Positioning System is used to pinpoint the location.
This information can then be used with a georeferenced
map to plot the location and movements of each
fish.
Fig. 11- The mobile antenna
Fixed
Antenna
Two stationary antennas
are situated on the bank of Clandeboye Channel.
One antenna faces the marsh and the other faces
Lake Manitoba. They are both connected to a
data-logging receiver that operates continuously.
When a fish leaves or enters the marsh, the
receiver records their radio frequency and logs
the time and antenna. We are then able to determine
which fish has either left the marsh or returned
from the lake.
Fig. 12- The fixed antenna
Aerial
Tracking
In 1999, we were also locating
fish using airplane-mounted receiving antennas.
Using an airplane we can track fish that have
moved further into the marsh or out into Lake
Manitoba, areas that are too large to survey
with a boat.
Fig. 13- The airplane mounted antenna
|
Pulling
a gill net on Clandeboye Bay.
Passing through
Clandeboye Channel.
Data recorded by
the fixed antenna receiver is downloaded
to a computer weekly.
Andrea and Dale
looking at data.
Photos-Ian
McCausland
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