Habitat use, movement patterns, and home ranges of coaster brook trout in Nipigon Bay, Lake Superior
Mucha, Jamie Michael
Master of Science
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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.