9710

• UCREFRP Catalog Number: 9710
• Author: Connolly, P.J., I.G. Jezorek, K.D. Martens and E.F. Prentice.
• Title: Measuring the performance of two stationary interrogation systems for detecting downstream and upstream movement of PIT-tagged salmonids.
• USFW Year: 2008.
• USFW - Doc Type: North American Journal of Fisheries Management
• Copyright Material: YES

PERFORMANCE OF PIT TAG INTERROGATION SYSTEMS

407

Creek, we divided low and high tlow at a depth of 16
cm over the top of the most embedded antenna
(equivalent to a stage height of 1.48 m and a flow of
0.38 m3fs). This depth corresponded to the maximum
read distance for BE-type PIT tags (the weakest tag
used in the watershed) at low EMF noise levels and
optimum orientation. In Beaver Creek, we reasoned
that low flow should be categorized as 22.9 cm or less
from the top of the most embedded antenna (equivalent
to a stage height of 1.69 m and a flow of 0.57 m3fs),
which was based on the water column height that
corresponded to the readable range of ST-type PIT tags
(the weakest tag used in the watershed) at low EMF
noise levels and optimum orientation for all six
antennas. While this method to separate low flow and
high flow ba'ied on water depth and read distance of the
weakest PIT tag type increased a'isurance that equal
probability of reading tags was achieved during periods
oflow flow, it did not assure it for periods of high flow,
and it did not incorporate enhancements for orientation
and EMF noise issues that later tags incorporated.
To help separate the events in which a fish wa'i likely
to have moved pa'it the entire interrogation system from
those when a fish did not complete the pa'isage (Figure
3), we developed criteria to select events suitable for
use in efficiency calculations (Table I). Based on the
frequency of time to pass the system. we selected a

I I

Fish 1 Fish 2 FiSh:> Fish 4 Fish 5 Fish .6

TABLE I.-Rules for delemlining when the detection of a
PIT tag qualifies as a fish-detection event and a fish-passage
event tor the pUl]Jose of estimating tlIe probability of detecting
a fish passing a PIT tag inlelTogation system composed of
tlrree arrays with two antennas in each array.

l. Eliminate detections of PIT tags in fish that were captured,
tagged, and released within 50 m of the antennllS.
2. \\-'hen a lish is detected at only one array. assume that it passed
all three aITays bnt was . not detected at the other two.
3. If a PIT-tagged fish is detected at more than one alllenna and the
time between the lirst and last detections does not exceed 18 min.
treat it as a tish-detection event. (The 18-min value correspOllds
to the 90th percentile of all potential fish-derection events for the
Rattlesnake Creek interrogation site.)
4. If the direction of mavement cannot be reasonably detemlined
from previous or later derections. do not use the detection event.
5. If a fish-detection event meets all of the criteria above, treat it as
a fish-passage event
6. Do not use a fish-passage event if the same fish is detected on
any antenna t2 h before or after this event.

value of 18 min, which corresponded to the 90th
percentile value, to be the time frame within which a
fish had to pass the interrogation system. To avoid
using fish that were swimming back and forth over the
antennas, we eliminated a fish passage event if the same
fish was detected by any antenna within 12 h previous
or subsequent to the first passage event. When we
compared this 12-h criteria (protocol 1) with a much
more restrictive criteria of I month (protocol 2),

Flow

l

Array A

Array a

Array C

FIGURE 3.-Possible routes and detections of PIT-tagged tish moving across a tlrree-array PIT tag interrogation system. A
straight vertical line that crosses a horizontal array line represents a successful fish detection. The movemenb of fish 1-5 would
be classified as tish passage events (see Table 1); that of fish 6 would not. The movements illustrated by the circles and ovals
would probably not be considered fish passage events.