Status of the Bow River
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In 2000, with the support of the Bow River Advisory Committee, regulations on the lower Bow River were changed in part to simplify and update the regulations were in existance for over 15 years.These regulation changes made in 2001 were indentified to deal with current emerging issues on the Lower Bow River |  |
On a continued basis, Fish and Wildlife in the Southeast region monitors the size structure and abundance of trout and mountain whitefish in an index section of the Lower Bow River. The index section is four kilometres in length and is located just downstream of the city limits. The most recent information has been collected in 1999, 2000, 2003, and 2005 (post flood). These assessments are completed in the late summer, early fall, typically in August or early September.
Summary
Rainbow Trout
Sizes – The relative size structure for rainbow trout has changed slightly in the last five years. Higher numbers of larger (> 38 cm or 15 in) trout were captured in the index section in 2003, when compared to our evaluations in 2005, however there is still a broad size class range available for anglers catch (i.e. up to 60 cm or 24 inches). There were also fewer of the smaller sized rainbow trout within the index study section when compared to previous years.
Abundance – Population estimates indicate relatively little change in population numbers. Despite the lower numbers found in 2005, the population abundance is still within the range of historic natural fluctuations. Rainbow trout population numbers have ranged between 250 and 1000 trout per kilometre, dating back to the mid 1980’s.
Brown trout
Sizes – Brown trout size distributions have remained relatively unchanged. In 2000 and 2003, there appeared to be a higher proportion of smaller sized brown trout, when compared with 2005. Overall, brown trout in this section cover all size classes, with a few exceeding 60 cm (24 in).
Abundance – Population estimates indicate a small reduction in all size classes, resulting in an overall lower abundance of total brown trout in the index section. However, similar to rainbow trout, the population abundance of brown trout remains well within the normal fluctuation of population changes noted in the Bow River.
Mountain Whitefish
Sizes – Unlike the rainbow and brown trout, our assessment of mountain whitefish suggests a large decrease in all sizes in 2005. The decrease was also evident between the 2000 assessment and the 2003 results. Mountain whitefish are still present in the index section and represent all size classes.
Abundance – As indicated by the decrease in the size distributions, the abundance of mountain whitefish has decreased. The lower abundance levels of smaller whitefish have been evident before the 2005 flood. Mountain whitefish greater than 28 cm have also decreased, however, there is no significant change. We have not collected abundance data on mountain whitefish prior to 1999, therefore we will re-assess this population within the next few years to see if the trend continues downward.
