Ram River Bull Trout Assessment, 2017–2022
Author(s)
Chad Judd, Mike Rodtka, and Zachary Spence
Summary
Bull trout (Salvelinus confluentus) in Alberta have decreased in population size and distribution compared to historical levels, and Saskatchewan–Nelson River populations are listed as Threatened under the Species at Risk Act. The federal recovery strategy identifies anthropogenic threats including habitat alteration and fragmentation, sediment introductions, non-native fish stocking, hybridization, and angling mortality as the leading causes of the decline in bull trout populations. The Native Trout Recovery Program is a collaboration between government and non-government organizations with the goal of assessing, recovering, and monitoring native trout populations throughout Alberta’s eastern slopes. Recovery of the populations can be achieved by mitigating the identified threats in the watersheds through actions such as restoring degraded habitat, reducing sediment inputs, suppression of non-native fish, and possibly changes in angling regulations. Our objective was to monitor the distribution and abundance of bull trout and other salmonids in the Ram River watershed in Alberta, which has been identified through the Native Trout Recovery Program as a priority watershed for mitigation measures and monitoring of the bull trout population.
We used backpack electrofishing gear to monitor bull trout and other fish species abundance and distribution from 2017 to 2021 in Ram River tributaries. We sampled between 8 and 12 sites per year throughout the study area; because of changes in study methods not all sites were sampled each year. During our study, we captured a total of 273 salmonids, including 182 bull trout. Bull trout ranged in size from 45 to 478 mm fork length. There were six sample sites that had zero fish captures the entire study period, while only one site had bull trout each of the five years of the study. Non-native brook trout (Salvelinus fontinalis) were found primarily in Makwa Creek and made up a small percentage of our overall catch. We did, however, capture suspected brook trout x bull trout hybrids at two sites during our sampling.
Water conditions early in our study made monitoring bull trout abundance in the Ram River impractical, so we used redd surveys (2018–2022) and fish counts (2019–2022) in Fall Creek to monitor adult bull trout abundance in the watershed. Fall Creek is a tributary to the Ram River used by migratory bull trout from the river for spawning. Redd counts ranged between 42 and 76 during the study period and together with our fish fence counts we estimated 1.2–1.3 spawners per redd. Independent redd surveys were between 79% and 124% of our best counts. Based on sixteen years of survey data collected by ACA, the bull trout population spawning in Fall Creek appears to fluctuate in a cyclic manner with no significant linear trend. Surveying Fall Creek for redds is a cost-effective technique for monitoring the Ram River’s migratory bull trout population.