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

10Cutthroat trout are prized by many coastal estuary, river and lake anglers, but regardlessthey are the least studied and understood of salmonids (Haig-Brown 1960, Anon. 1996).Ironically, their apparent guarded profile by anglers has ultimately contributed to ascarcity of habitat and stock status data on coastal cutthroat trout (Raymond 1997),resulting in little trend data on their populations and sport fisheries in British Columbia.Although coastal cutthroat are not routinely censused in their natal streams, as aresteelhead and salmon, their geographic distribution is well documented, and they arewidely spread in their range from northern California in the Eel River drainage to SouthEast Alaska in Prince William Sound (Costello and Rubidge 2004). Thus, they areknown to be very broadly distributed throughout coastal British Columbia (Slaney et al.1997), and they are a separate sub-species from westslope cutthroat trout (O. c. lewisi)which inhabit the south eastern Interior. Comparatively, the mature coastal subspecieshas a characteristically large jaw that extends past the eye, accommodating a highlypiscivorous adult life history. Coastal cutthroat are known to have highly variablephenotypic traits and life histories (Costello and Rubidge 2004), where their habitats arehighly associated with the Pacific rainforest belt (Trotter 1997). Thus, they occur withintwo ecoregions in British Columbia: the Coast and Mountains, and the GeorgiaDepression. Habitats range from small streams to large rivers, bogs to sloughs, ponds tolarge lakes, and coastal lagoons to estuaries and ocean beaches.Life history traits are the most complex among salmonids and include at least four typesor forms including resident, fluvial, lacustrine and sea-run (Anon. 1997). These formsare present throughout their entire geographic range (Trotter 1997). In addition to thiscomplexity, the relationships between populations with these various life histories largelyremain unknown (Anon. 1997), but mixed life histories within the same population havebeen documented (Anon 1997).As the fisheries literature suggests, many cutthroat populations are depressed relative totheir historical abundance because they have been widely subject to habitat loss anddegradation, as well as over-fishing (Hall et al. 1997). Numerous local extirpations havebeen documented in the Pacific Northwest (Costello and Rubidge 2004), for which pastintensive hatchery practices are also implicated in some areas of Oregon and Washington.Further, fishing mortality is considered an important source of risk, based on statusreviews in the 1990s associated with the US federal Endangered Species Act (ESA)(Johnson et al. 1999). Clearly, in the US Pacific Northwest, it is the anadromous formthat is of greatest conservation concern owing to some serious declines in major stocks.The status of cutthroat has also been reviewed in British Columbia, albeit highlyconstrained by the sparseness of available data. Further, anadromous cutthroat weresurveyed qualitatively as part of a larger American Fisheries Society investigation of thestatus of salmon and trout. Five coastal cutthroat populations in the Lower MainlandRegion were judged as extinct, and four as at high risk of extinction, but the status ofmost (80 %) were unknown (Slaney et al. 1997). Populations in adjacent streamspossibly formed a separate stock, which added complexity to the review. More recently,the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) examined