Lake Level – Fish and Wildlife


A section from the Lake Level Monitoring report contained in Staff Report from the December 13, 2012 board meeting material.  This section drafted by district staff.

LLRpt Fig 16Devils Lake is home to a genetically distinct line of federally listed Coho Salmon. These fish make their upward migration in the winter period, when the lake is not impounded, but their outward migration occurs from May to Mid July which is typically a period of impoundment. In 2012 the impoundment period was reduced to beginning no earlier than June 1st, with an anticipated impoundment starting date of June 15th, based on lake level at the time. Historically the lake was impounded from April 15th. The District had a practice of pulsing the dam every other night from May 15 to May 31 in an attempt to mitigate some of impacts to juvenile fish trying to make their way to sea. Non-native ambush predators such as large mouth bass and other piscivorous fish may take advantage of the shadowy, narrow outlet the juvenile Coho would necessarily have to traverse in their escapement.

LLRpt Fig 17The consequences of not impounding water until at least June 1st, all but did away with this potential impact through the peak period of migration. Impoundment beginning in June however does still require a change in the essential behavior pattern for lategoing fish as Migration runs through Mid July. Additionally Sea run cutthroat another native anadromous fish species have migration patterns that only start in June and extend even further through the summer to Mid August. Should the District impound as early as June, no mitigation to the impacts on these fish would be accomplished. Similarly Pacific Sea Lamprey have an inward migration period from February to October, so the dam serves as a physical barrier to their upward migration at as significant portion of the time irrespective of the date it is put in. The District has though committed itself to a retrofit of the structure for the 2013 impoundment season to be more Lamprey friendly by providing curved surfaces more typically of river rocks through the weir which the lamprey necessarily must pass during impoundment.

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Filed under DLWID, Lake Level

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