Lake Sturgeon Radio Telemetry Study
Ontario
Ministry of Natural Resources
Lake Superior Management Unit
Natural resource agencies in Canada
and the United States have developed a Lake
Sturgeon Rehabilitation Plan for Lake Superior.
The goal of the plan is to maintain, enhance and rehabilitate
self-sustaining populations where the species historically occurred basin
wide.
One
of the strategies to achieve this goal is to protect and rehabilitate habitats
for all lake sturgeon life stages. With
support from the Ontario Federation of Anglers and Hunters, the Great Lakes
Sustainability Fund and the Lake Superior Binational Program, the Lake Superior
Management Unit has initiated a radio telemetry study of adult and juvenile lake
sturgeon in the Kaministiquia River (figure 1).
This study will allow us to determine the seasonal distribution and
movements patterns of these fish and identify important habitat areas (i.e.
spawning and feeding).
MATERIALS
AND METHODS
From Sept 6 to October 2/ 2000, lake sturgeon were captured using 114 (4.5”),
216 (8.5”), 241 (9.5”), 254 (10”), 305 (12”) and 381 mm (15”)
stretched mesh, multifilament gill nets. Net
lengths were 50, 85 and 100 yards. All
sturgeon were sampled for fork length, total length, legal length, weight and
were tagged with a five digit, orange floy tag applied along the left hand side
of the dorsal fin. Some sturgeon
were also tagged with a six digit, clear disc tag applied anterior to the dorsal
fin. Sex determination was
attempted by internal examination using an autoscope.
Twenty Advanced
Telemetry Systems radio transmitters, with trailing external whip antenna, were
surgically implanted into the body cavities of adult and juvenile lake sturgeon.
Sturgeon were selected for transmitter placement so that the weight of
the transmitter did not exceed 2% of the fish weight.
Seventeen 75g tags (figure 2) with a life of 1095 days, two 26g tags with
a life of 400 days and one 20g tag with a life of 280 days were used.
Each transmitter is coded with a unique frequency between 150.000 –
151.990 MHz.
Prior
to surgery the magnet taped to the transmitter was removed to activate the tag.
The receiver was then turned on, locked on the frequency of the tag and
the volume turned up until the pulse of the tag was heard.
This verified the tag was functioning properly before implantation. The surgical procedure was as follows.
· A
solution of 1.2 ml clove oil to 10.8 ml ethanol was used as an anesthetic.
· 36 ml of
the clove oil/ethanol solution was mixed into 60 litres of water.
· Fish were
immersed in a tub containing the anesthetic for approximately 5 minutes
depending on fish condition and size.
· Once
immobilized, the fish was placed belly up in a foam lined, v-shaped tagging
trough.
· A squirt
bottle containing the anesthetic solution was used to irrigate the gills.
This ensured the fish would not recussitate during the surgery (figure
3).
· A
scalpel, (# 60 blade) was used to make a 2 inch incision just off the midline of
the body, half way between the pectoral and pelvic fins (figure 3).
· A 4”
(10cm) # 11 Jamshidi Bone Marrow Biopsy/Aspiration Needle was used to make a
small hole approximately 2 cm behind the main implant incision (figure 4).
· The end
of the needle was pushed forward until the end was visible in the main incision.
· The
antenna was then threaded into the end of the needle and pushed far enough until
it exited the body.
· The tag
was then inserted into the body cavity (figure 5).
· At this
point the gills were then irrigated with water to wash off the anesthetic and
allow the fish to start recovering.
· The main
incision was then sutured using Ethicon absorbable nylon prethreaded cutting
sutures (figure 6).
· For 10-15
minutes the fish was allowed to recover in a tub that was situated in the river.
· Once able
to swim off the fish was released.
RESULTS
Fifteen overnight gill net sets and 16 short term sets were carried out between
September 6 and October 2, 2000. Twenty
sturgeon implanted with radio transmitters ranged in weight from 1.7 kg to 24.7
kg. Forty additional sturgeon were
captured during the netting.
Recaptured
individuals included three from 2000, ten from 1998 and one from an unidentified
source (orange floy tag # 12090). One
radio-tagged fish was recaptured 14 days after the surgery and the incision was
healing well.
None
of the fish could be sexed based on internal examination.
All fish have been located and are moving throughout the Kaministiquia River.
