Coastal Cutthroat Trout as Sentinels of Lower Mainland Watershed ...

625.2.4. Cutthroat Stream Stock Management RecommendationsFor effective management of Lower Mainland cutthroat streams, a key question is howmuch effort should be spent on an expanded inventory of coastal cutthroat streams versusother management activities. The latter can provide trend data on stock status, the resultsof which can be directed at conservation. Until limited funding is expanded considerably,inventory of all cutthroat streams, including their lengths and areas, should not become apriority. Although this has merit for a much smaller number of steelhead streams withdimensions that are readily quantifiable, this is not the case for a plethora of cutthroatstreams along the coast of British Columbia. Rather, further documentation of stream useand densities of coastal cutthroat should be directed in order of priority at:• anadromous (sea-run) and/or fluvial (river-run) cutthroat streams, which are atgreater conservation risk than lacustrine (lake) stocks, with highest priority givento cutthroat-coho streams that are at risk from urban development in Region 2;• key cutthroat production streams, given that 13 of a large sample of cutthroatstreams in 1979 accounted for 85 % of estimated parr abundance; and• stock and habitat assessments of streams from Chilliwack to Hope (includingHarrison River tributaries) which did not receive earlier coverage by DeLeeuwand Stuart (1980). These may be dominated by fluvial river-run stocks ofimportance to the Lower Fraser sport fishery.Overall, there is currently insufficient recent data from cutthroat streams of the LowerMainland Region to be able to make definitive inferences about stock status. However,smolt and adult enumerations at Salmon River suggest a downward trend. Smolt countsat this index site should be continued and additional index streams for juvenile densitiesshould be selected in locations where one to two years of intensive population samplingwas conducted earlier. However, stream reaches and density data should be re-checkedto ensure suitability. Additional stock status work is urgently required given the declineof sea-run cutthroat trout in Oregon and southern Washington State, as graphicallysummarized earlier. The overriding objective should be to establish trend data for a set ofcutthroat streams, whereby population sampling is repeated periodically.Because there is circumstantial evidence of impacts of hatchery-wild interactions amongsome large populations of sea-run cutthroat in US waters (e.g., Figure 14), cautionarypractices are warranted in the Lower Mainland Region. Stocking should be consistentlyrestricted to the lower most reaches, and largely to non-nursery streams such as the StaveRiver, lower Harrison River (Kilby) and the mainstem lower Fraser River. Similarly,there is a need to monitor the ecological and genetic effects of residualism, includingpotential hybridization with steelhead, such as at the Alouette River and the SeymourRiver. From a genetics perspective, it is important that there is a similar policy forcutthroat and steelhead.Analyses of cutthroat scales for marine elements (strontium, iridium, or the ratio ofstrontium to calcium) and electronic tracking are needed to confirm if Lower Fraserstocks are indeed sea-run versus river-run populations. Some stocks of cutthroat trout ofthe Lower Fraser are likely fluvial or river-run stocks, or both, and some may also inhabit