Chapter 5 – Anadromous Movement and Estuarine Habitat Use of Coastal Cutthroat Trout

Principal Investigator: Allan Costello


The Cutthroat Trout Protocol was designed to assess the potential effects of the Kitimat LNG facility on the use of Bish Creek estuary, near-shore, and marine environments by coastal cutthroat trout (Oncorhynchus clarkii clarkii). The coastal cutthroat trout is an anadromous fish with an extended nearshore-marine residency period, and one known to be sensitive to anthropogenic activities affecting freshwater habitat quality. Unlike pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon, which utilize the estuarine environment around Bish Creek and Cove for a relatively limited time prior to migrating offshore, anadromous coastal cutthroat trout remain in the nearshore marine environment throughout their life, often in the immediate vicinity of their natal stream. They repeatedly move between freshwater and nearshore-marine habitats to access productive habitats and locally abundant food resources like salmon fry (Giger 1972; Behnke 1992; Pearcy 1997; Trotter 1997). Furthermore, the species is listed as of special concern in BC and are known to be particularly sensitive to anthropogenic effects to their freshwater habitats (Johnson et al. 1999; Costello and Rubidge 2005; Slaney 2005).

Throughout its range, the number and distribution of coastal cutthroat trout populations have been steadily declining in response to the cumulative impacts of habitat loss and degradation, overexploitation, and detrimental interactions (i.e., competition, predation, hybridization) with introduced species (Allendorf and Leary 1988; Liknes and Graham 1988; Nehlsen et al. 1991; Johnson et al. 1999; Costello and Rubidge 2005; Shepard et al. 2005). The declines over the last century clearly indicate that the greatest threats to cutthroat trout are the anthropogenic manipulation and degradation of the environment in which it lives. All available information for BC suggests that many populations are depressed relative to historic levels, particularly in the Georgia Basin where numerous local extirpations have been documented (Costello and Rubidge 2005). Although believed to be less impacted than populations further south, the status of most anadromous salmonids along the north coast of BC is largely unknown outside of human-populated areas where declines in Coho (O. kisutch), steelhead (O. mykiss) and coastal cutthroat trout were first noted in the early 1980s. At that time, it was apparent that anadromous, fluvial, and resident forms of coastal cutthroat trout in some parts of the region were being overharvested to the point where populations were no longer capable of sustaining even modest fishing pressures. Severe harvest restrictions, reduced catch limits and closures were recommended for the Terrace-Kitimat area to prevent further declines and extensive habitat restoration, inventory and assessment of remaining stocks was deemed ‘mandatory’(Whatley 1984).

Anadromous cutthroat appear to rely heavily on marine-derived protein (e.g., meiobenthic fauna, salmon fry and smolts, juvenile smelt and perch, etc.) that promotes overwintering survival and reproductive success. Rocky beaches, eelgrass (Zostera marina), or kelp beds near creek mouths provide excellent estuarine habitat for coastal cutthroat, especially if structures such as old pilings and docks are located nearby. Construction of marine terminals and jetties at Bish Cove could, therefore, potentially benefit anadromous cutthroat, as they often use the cover provided by such structures to evade marine predators.