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The McIntyre River projects are cooperative ventures between the Northshore Steelhead Association (NSSA) and the Lake Superior Management Unit (LSMU). The main objective of the work involved on this system is to monitor the status or health of the rainbow trout population. Two main projects have been underway for a number of years. One of the projects is the Adult Rainbow Trout Fish Counter Project, and the other project is the YOY Rainbow Trout Monitoring Project.
Adult Rainbow Trout Fish Counter Project
This project began in 1999, and is designed to determine the numbers of adult rainbow trout migrating from Lake Superior to the sections of stream above a fish ladder located on Lakehead University's campus (Figure 1). After ice-out each year, a Resistivity Fish Counter is installed above the fish ladder at Lakehead University to determine the numbers of adult rainbow trout migrating upstream beyond this point.
Background
The project began with the installation of the Lake Tamblyn fishway in 1989. The dam at Lake Tamblyn was a barrier to migration under all but perfect water conditions (warm and at adequate flows) when Steelhead were able to navigate through the original and inefficient Denial fish ladder. This caused fish to bottleneck at the dam, and unless conditions were perfect, often not get by at all, leaving the productive upstream areas devoid of adults and their progeny. The new Fishway was expected to eliminate this problem, and provide an ideal location for assessment work on the migratory population.
Concerned anglers perceived that the dam, combined with years of heavy fishing and harvest had left the McIntyre Steelhead runs a shadow of their former glory. Data obtained from the Cooperative Angler Program revealed that the population was, indeed, under stress, but an accurate population estimate was next to impossible. After consultation between NSSA and LSMU, it was decided that a Resistivity Fish Counter would be installed at the fishway, with expenses to be shared. The Resistivity Fish Counter utilizes an interrupted electrical signal to count each upstream movement over the dam and to estimate the size of the fish. This project, combined with a renewed emphasis on angler collected length and scale information, has provided many years of population data, and will likely continue to be used annually. At the time (1999), it was the first Fish Counter of its type in the Lake Superior basin, and will help to ensure that the McIntyre River is managed so that populations do not continue to decline, but rebound and grow to their potential.
Rainbow Trout Population Assessment Using
Fish Counter Technology
The introduction and
naturalization of rainbow or steelhead trout into Lake
Superior has provided anglers with the benefit of fishing
for this renowned sport fish. Rainbow trout are one
of the most popular fish sought in Lake Superior and
in tributary streams. In the past decade, however, concerns
for declining populations have surfaced throughout the
lake.
One of the recommendations
of the Rainbow Trout Management Plan (draft version) for Lake Superior
was to implement restrictive regulations for rainbow
trout on the McIntyre River as an experimental exercise
on a heavily exploited system. The McIntyre River originates
at Trout Lake and flows through the City of Thunder
Bay before emptying into Lake Superior in the Thunder
Bay Harbour. The river supports a self-sustaining population
of rainbow trout (steelhead) that migrate up the river
each spring to spawn. During the spawning migration,
rainbow trout are actively sought by anglers particularly
in the stretch between the Harbour Expressway and Lakehead
University. As part of the Management Plan, the North
Shore Steelhead Association and the Lake Superior Unit
are conducting a long-term rainbow trout monitoring
program on the McIntyre River. The goal of the project
is to gain a better understanding of the population
dynamics of rainbow trout in Lake Superior and to determine
the status of an individual stock in a heavily exploited
system.
A daily catch
and possession limit of one fish with a minimum total
length of 69 cm (27 in) was put into place in 1999. To quantify
the effect of this regulation change on rainbow trout
numbers a resistivity fish counter (Aquantic 2100C)
was installed at the upper end of the McIntyre River
fishway at Lakehead University in the spring of 1999, 2000, 2001, 2003, and 2004 (Figure 2). The typical phases of the migration that occurred during each year of monitoring are depicted in Figure 3. The counter detects the passage
of fish across an array of three electrodes. The counter
continually monitors the resistance of the water above
the counting array and calibrates for changes in this
resistance every 30 minutes. When a fish passes over
the three electrodes, a change in resistance occurs,
which is recorded and analyzed by the counter using
a firmware algorithm to determine if it fits a typical
fish pattern. Should the counter assess that a fish
has passed over the array (based on this comparison),
the time, direction of travel, and peak signal strength
(change of resistance measurement) of the fish event
is recorded and stored for later downloading and analysis.
In general, the numbers of rainbow trout that are estimated to have passed through the fish counter over the years have increased (414 in 1999, 413 in 2000, 361 in 2001, unknown in 2002, 493 in 2003, and 952 in 2004 (Figure 2).
While an accurate
estimate of numbers of adults is extremely valuable,
some idea of the age composition of the run was also
required. In 2000 and 2001 anglers collected biological
information from rainbow trout angled in the McIntyre
River. Anglers sampled fish for fork length, sex, and
removed a scale sample for aging purposes.
Anglers sampled
186 rainbow trout ranging in length from 200 - 760mm
with an average length of 563mm. Rainbow trout ranged
in age from 2 - 10 years but were dominated by four
and five year old fish (view Cooperative Angler - McIntyre River PDF). The repeat spawning
rate for females was 73% (30 of 41) in 2000 and 65%
(51 of 78) in 2001. The duration of stream residence
before migration to Lake Superior ranged from 1-3 years
but was dominated by two-year-old smolts. Rainbow trout
spent approximately 2 years in Lake Superior before
returning to the McIntyre River to spawn for the first
time. The duration of lake residence before spawning ranged from 1-5 years, but was dominated by 1-2 years for males and 2-3 years for females.
The main objective
of the Rainbow Trout Management Plan (draft version) is to maintain
healthy rainbow trout populations in Lake Superior and
its tributaries. To assess if this objective is being
met the following targets have been established:
- Maintain a high
percentage of repeat spawners (50-55%) in rainbow
trout stocks over one generation.
- Maintain a wide
range of year classes in rainbow trout populations.
- Ensure each of three
year-classes represent 15% or more of the adult population.
Population dynamics indicate that this
population is exhibiting the characteristics of a healthy
fishery as established in the Management Plan.
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