Distribution and Abundance of the Migratory Bull Trout Population in the Castle River Drainage (Year 4 of 4)
Alberta’s bull trout populations have declined over the last century due to anthropogenic disturbances, including habitat fragmentation and degradation, migration barriers, introduction of non-native fish species, and overharvest. In southwestern Alberta, bull trout distribution has been reduced to approximately 31% of its historical range. Current populations, all of which are At Risk of extirpation, exist only in headwater streams. The abundance and distribution of these remnant populations are unclear. ACA has completed abundance and spawning habitat assessments in the Castle River drainage to update the status of these remnant populations. During fall 2014, we installed fish traps in South Castle River, Carbondale River and Mill Creek to capture bull trout migrating downstream. We marked all adult bull trout (≥300 mm fork length) with an internal transponder tag to track individuals during recapture events. We captured a total of 191 adult migratory bull trout in three major spawning streams: 73 fish in South Castle River, 89 in Carbondale River, and 29 in Mill Creek. We conducted redd (fish nest) counts in spawning streams and observed 211 redds in a total of 68 stream kilometres: 48 in South Castle River, 14 in West Castle River, 72 in Mill Creek, and 77 in the Carbondale River drainage. The 2014 field season marks the final year of the study. Since 2011, we have captured and marked 493 adult bull trout and documented spawning habitat use throughout the major streams of the Castle River drainage.
Alberta Environment and Parks, Devon Canada Corporation, Shell Canada Energy
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|Distribution and Abundance of the Migratory Bull Trout Population in the Castle River Drainage (Year 4 of 4)||2014-2015||1|