7979

• UCREFRP Catalog Number: 7979
• Author: Tyus, H. M.
• Title: Fish Radiotelemetry
• USFW Year: 1982.
• USFW - Doc Type: Theory And Application For High Conductivity Rivers.
• Copyright Material: NO

Table 4. Water conductivity (umho/cm)a, Green River, Utah 1980. Temperature
rounded to degrees Centigradeb.
whip antenna. Each time contact was re-established, and the fish remained in
the same spot. When the boat was anchored at this spot, the loop antenna was
virtually useless.
Conductivity Temperature
Standards
~ The fish surfaced at times, and reception became very strong, almost
Month n range z z conductivity "deafening." Reception at other times was very weak. Apparently, the fish
ascended and descended in the water column, and a 3 m depth was the limit of
April 27 420- 770 443 9 620 radio reception at the estimated conductivity of 800 to 1000 pmho.
May 13 245- 625 334 15 401 On April 21, rising water flooded the holding pen, and three implanted
fish escaped. One of these fish was located in midchannel not far from the
June 11 175- 291 223 19 252 holding pen. On April 22, this fish (No. 165) was re]ocated in the same
general area in water 1.3 m deep. The signal was adequate for the whip antenna
July 9 240- 291 433 18 519 from a distance of about 80 m. Conductivity was about 940 umho.
August 7 750-1200 895 25 895 On April 24, fish No. 028 was located about 3 m from the bank, when the
conductivity was 700 pmho. The reception was identical to that experienced
September 6 610- 950 809 21 890 with fish No. 001 on April 15 at a conductivity of 812 pmho. Radio reception
with the elevated whip was adequate to over 100 m, while the loop antenna was
useful only at distances less than 50 m and usually between 25 to 30 m.
sCorrected to 25° C. Figure 7, illustrating receving antenna efficiency, was drawn from results
obtained using crude experimental techniques with "naked" transmitters. It
bReadings taken in the Green River immediately below the Duchesne River displays general relationships between water depths and the distance an antenna
are omitted due to the very high conductivity in the Duchesne River. can detect signals. At 2 m deep, the most effective antenna was the whip
antenna with a ground reference plane. The whip antenna without a base was
less effective, but -still more effective than the loop antenna. The loop
antenna was useless at distances beyond 60 m.
The three transmitters performed similarly, although the small AVM fish
module seemed to produce a slightly better signal. This could have been a
function of transmitted power or due to auditory quality perceived by the
radio receiver. This type of performance was unexpected because the module had
been retrieved from an implanted fish after being in operation for more than
' four months. Some fish modules produced a "better sound" than others, depend-
ing to some extent on the relative length of the pulsed transmission. However,
some tones were "mushy" and some "sharp". Sharp bursts of sound are more
desirable for radio reception.
Ranges of transmitters can be Increased by implanting transmitters in
fish. According to Ringe (pers. comm.), results with Smith-Root antennas
anchored in the mouth of salmon give a significant increase in apparent signal
strength over "naked" transmitters. However, we did not experience more than
a minor increase in range when transmitters were fmplanted.
Conclusions
Results of this study indicate that it is possible to use radiotelemetry
to follow movements of fish, even in rivers where conductivities are relatively
high. Field sampling produced better results than expected, mainly because of
shallow water and the behavior of the fishes.
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