DEVELOPMENT OF A HIGHLY EFFICIENT SMOLT TRAP FOR USE IN
HEAVILY DEBRIS LADEN STREAMS
An increasing number of ecological studies on Atlantic salmon populations
rely on data collected from a large number of individuals. The individuals
are usually tagged and sampled multiple times creating an extensive
history of growth and movement for each fish. Sampling of the individuals
as they smolt is necessary to complete the development history of the
individuals and to obtain accurate population estimates. In these studies
it is ideal to sample each surviving tagged fish is when it smolts.
Many study areas need a portable trap that is highly efficient at capturing
all the migrating individuals. The traps also need to withstand high
flow events in streams with a large amount of debris. A portable trap
design that is sufficient for our needs does not exist. Therefore the
objectives of this study are 1) Develop a smolt trap that can be utilized
during low and high flow events under heavy debris loading, 2) evaluate
the trap in the 20-foot wide flume at the S.O. Conte Anadromous Fish
Research Center, 3) estimate the efficiency of the trap in the field
using mark and recapture, 4) track smolt movements using radio telemetry
as another estimate of efficiency and to determine how they encounter
the trap.
Initial tests of the trap currently used in the field were conducted
in the 20-foot wide flume at the Conte Anadromous Fish Research Center
during the fall of 2000. The purpose of these tests was to locate the
weaknesses of the current trap under various flow regimes and determine
what areas need to be addressed. Using the information gathered from
those tests new traps were designed and tested in the flume in the winter
of 2000-2001.The best trap design (a rotary screw trap and resistance
board weir hybrid) was installed in the field in the spring of 2001.
The new trap design continued to successfully fish after the old design
was washed out during a high flow event. Stratified mark and recapture
sampling in the field estimated the efficiency of the trap at 66.7%.
Modifications of the new design were tested in flume during the fall
of 2001. The modifications will be tested in the field during the spring
smolt run of 2002. As in the spring before, efficiency will be determined
by stratified mark and recapture samples. The efficiency of the trap
will also be further evaluated through the use of radio tracking of
smolts.
