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

61Past brood stock capture at natal streams indicated little straying of hatchery adults fromriver stocking locations into natal streams (K. Scheer pers. comm. 2004), and it remainsuncertain where hatchery fish spawn. There is a risk of wild spawners breeding withhatchery spawners that have lower-fitness. For example, timing of spawner migration ishighly heritable and may differ between wild adults and hatchery adults, as documentedin steelhead (Chilcote et al. 1984). Mixing different Fraser stocks of different timingwould tend to create panmixis of timing and other genetic migratory traits, which couldbe detrimental if sea-run stocks were mixed with river-run or lake-river stocks. Thus,there is a need to monitor natal streams for incidence of wild and hatchery adults wherestocking rates are high and the catch ratio of hatchery to wild adults is high (i.e., as at theAlouette River). DeLeeuw and Stuart (1982) estimated a wild parr population of 5,050from Alouette River tributaries which was estimated to yield 404 adults. Given that18,000 smolts are released into the lower Alouette River, several hundred hatchery adultscould potentially return to the system. Therefore, management studies are needed toexamine abundances of wild and hatchery adults in the mainstem and nursery tributaries,as well as the abundance of wild juveniles compared to earlier estimates made byDeLeeuw and Stuart (1980).Stocking targets could be further reviewed in terms of providing angler opportunitieswith the least risk to wild cutthroat production. For example, current stocking ofcutthroat smolts at the Alouette River includes triploids, and if their incidence is lowamong brood fish collections, a decision may have to be made whether to treat theAlouette River as a hatchery stream relative to anadromous cutthroat stocking. Also, theCapilano River is degraded from a hydrologic and fish stock perspective, to the extentthat salmonid stocks require hatchery support. Yet from a 1980 creel survey, theCapilano River was rated by Lower Mainland anglers as the most popular stream to anglecutthroat. Thus, significant smolt releases could be redirected to lower Capilano Riverwith little genetic or ecological risks, possibly using a captive brood stock from BrothersCreek reared at a nearby hatchery such as Seymour River 1-year smolts. This wouldpotentially generate a major cutthroat fishery in proximity to the population centre ofVancouver, and reduce stocking rates and risks at wild cutthroat streams (such asAlouette River system) in the Lower Mainland Region.There may be viable alternatives to cutthroat smolt stocking in the Alouette River system.Of about one million m 2 of anadromous stream area, only 36,800 (4.0 %) is suitable forcutthroat trout production (DeLeeuw 1981). Regardless, the Alouette River systemranked 2 nd overall in potential for stream enhancement/restoration. An estimatedcapability of 1,377 adults was predicted versus existing 404 (from parr) at the time ofassessment, which could readily compensate for fewer hatchery fish. The best streamsfor habitat restoration were Jacobs Creek reach 2, reach 1 of the third tributary of theAlouette River, and the third reach of the North Alouette River. Fry stocking in underrecruitedreaches was also listed as a priority (DeLeeuw and Stuart 1980), and if nativefry were well dispersed at the unfed stage, genetic impacts from stocking would benegligible.