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Recovery Strategy for Nooksack Dace
The Nooksack dace is a small (<15 cm) stream-dwelling cyprinid (minnow). It is considered a subspecies of the widespread and common longnose dace Rhinichthys cataractae. Within Canada it is known from four lowland streams in British Columbia’s Fraser Valley. The global distribution includes approximately 20 additional streams in north-west Washington (McPhail 1997). The Nooksack dace is extirpated from some tributaries in Canadian watersheds where it was abundant in the 1960s (McPhail 1997). Its current status in Washington State is unknown.
Nooksack dace are strongly associated with riffle habitats (McPhail 1997) and the proportion of riffle in a reach is the strongest predictor of their presence (Pearson 2004a). Young-of-the-year fish require shallow pool habitats in close proximity to the riffles inhabited by adults (McPhail 1997). Home range size is typically very small (<50 m of channel) although a few individuals venture for at least hundreds of metres (Pearson 2004a). This suggests that clusters of riffles may contain semi-isolated subpopulations and that metapopulation dynamics may be important at the watershed scale(Pearson 2004a).
Nooksack dace populations appear to be most vulnerable to seasonal lack of water, habitat loss to drainage activities, sediment deposition, and riffle loss to beaver ponds. Introduced predators are widespread in the range but probably have minimal impacts on Nooksack dace because of lack of habitat overlap. Hypoxia and toxicity are significant threats in some sections of at least one watershed, but do not threaten the species throughout its range.
Critical habitat for Nooksack dace has not been formally described in this recovery strategy. The Recovery Team has compiled scientific data which will assist in the definition of critical habitat, and this information should provide the basis for an official designation of critical habitat through the action planning process, which will include socioeconomic analysis and consultation with affected interests. Critical habitat for Nooksack dace should be defined at the reach scale, and should include specific features such as riffles, shallow pools, and riparian habitat. Further studies are required to confirm the presence of other Nooksack dace populations and their critical habitats, and to characterize specific threats. Defining critical habitat will contribute to the refinement of recovery objectives and the management of activities that impact the species.
Recovery of Nooksack dace populations is both technically and biologically feasible. It will involve the establishment and/or maintenance of sufficient high quality riffle habitat in each creek to maintain a population. Specific requirements will vary, but will generally include in-stream flow protection, restoration of riffle habitat and, in some circumstances, restriction of beaver impoundment. Some management will be required in all watersheds.
The goal of recovery is:
To ensure long-term viability of Nooksack dace populations throughout their natural distribution in Canada.
The recovery strategy has three objectives, each of which is discussed in detail in the text.
- For all currently and historically suitable habitats in native streams to be occupied by 2015.
- To increase Nooksack dace abundance to target levels in all watersheds by 2015.
- To ensure that at least one reach in each watershed supports a high density of Nooksack dace.
Eight broad strategies have been identified in support of these objectives:
- Protect, create and enhance riffle habitat in habitat reaches with high potential productivity.
- Establish or maintain adequate baseflow in all habitats with high potential productivity.
- Reduce sediment entry to creeks.
- Ensure the integrity and proper functioning of riparian zones throughout watersheds.
- Reduce habitat fragmentation.
- Encourage stewardship amongst private landowners and the general public.
- Minimize toxic contamination of creeks.
- Minimize impacts of introduced predators.
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