| dc.description.abstract | Coaster brook trout are one of two salmonine species native to Lake
Superior. Abundant and widely distributed in Lake Superior a century ago, they
have been reduced to a few remnant stocks due to exploitation and habitat loss.
Twenty coaster brook trout, captured from Nipigon Bay, Lake Superior were
surgically implanted with radio transmitters and were located from June 1999 to
October 2000. Coaster brook trout locations were used to determine the
characteristics of utilized lake habitat, identify streams and the critical habitat
characteristics within them utilized for spawning, and establish home ranges and
movement patterns on a daily and seasonal time scale. A total of 638 locations
were obtained during the tracking period with 483 locations within Nipigon Bay
and the remaining 155 within tributary streams. Coaster brook trout were located
almost exclusively within the shallow nearshore areas of Nipigon Bay with 92% of
locations in areas less than 7 m deep (mean depth = 3.4 m), and 94% less than
400 m from shore (mean distance to shore = 116.1 m). Coaster brook trout
inhabited deeper areas (ANOVA, F=3.533, p=0.002) with steeper shoreline
slopes (ANOVA, F=2.562, p=0.013) during July and August when the water
temperature of shallow nearshore areas became higher than their tolerable limit.
Following selected individuals for 24 hours revealed coaster brook trout utilized
deeper areas during daylight hours and moved to extremely shallow nearshore
areas during the night (ANOVA, F=3.187, p=0.02). Home range estimates for
individual coaster brook trout using a 95% fixed kernel varied from less than 1 km
to 185 sq. km. in size. Home range size was not correlated with the number of
locations for the individual (r2=0.046), or fork length (r2=0.009). Tagged coaster
brook trout began ascending streams during late summer in both 1999 and 2000.
The mean residency time for brook trout in spawning tributary streams in 1999
was 46 days. Spawning occurred in early October with most tagged coaster
brook trout returning to Lake Superior by mid-October. Four different streams
were used by tagged coaster brook trout, with all brook trout entering streams
exhibiting strong spawning site fidelity. Catchment size of spawning streams
varied from 8.38 sq. km to 288.04 sq. km, but stream reach characteristics of
spawning areas were similar, exhibiting a moderate gradient, riffle-pool
complexes, coarse sands and gravels, and groundwater input. These results
suggest that coaster brook trout utilize specific areas depending upon the time of
year. Protection of these identified areas is critical to maintain these remnant
natural stocks. | |
