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Recovery Strategy for the Nooksack Dace (Rhinichthys cataractae) in Canada

Executive summary

Background

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).

Threats

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

Critical Habitat for Nooksack dace consists of reaches in their native creeks and that consist of (or are known to have previously consisted of) more than 10% riffle by length. It includes all aquatic habitats and riparian reserve strips of native vegetation on both banks for the entire length of the reach. Reserve strips are continuous and extend laterally from the top of bank to a width equal to the widest zone of sensitivity (ZOS) calculated for each of five riparian features, functions and conditions.  The ZOS values are calculated using methods consistent with those used under the British Columbia Riparian Areas Regulation (Reg. 837) under the Fish Protection Act (S.B.C. 1997, c. 21). The combined length of critical habitat for Nooksack dace is 33.1 km (of 93.9 km of surveyed stream channel).

Recovery

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.

  1. For all currently and historically suitable habitats in native streamsto be occupied by 2015.
  2. To increase Nooksack dace abundance to target levels in all watersheds by 2015.
  3. 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:

  1. Protect [1], create and enhance riffle habitat in habitat reaches with high potential productivity.
  2. Establish or maintain adequate baseflow in all habitats with high potential productivity.
  3. Reduce sediment entry to creeks.
  4. Ensure the integrity and proper functioning of riparian zones throughout watersheds.
  5. Reduce habitat fragmentation.
  6. Encourage stewardship amongst private landowners and the general public.
  7. Minimize toxic contamination of creeks.
  8. Minimize impacts of introduced predators.

[1] Protection can be achieved through a variety of mechanisms including: voluntary stewardship agreements, conservation covenants, sale by willing vendors on private lands, land use designations , and protected areas.