COSEWIC Assessment and Update Status Report on the Nooksack dace in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Tables
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status Designations
- Technical Summary
- Acknowledgements, Authorities Contacted, and Information Sources
- Biographical Summary of the Report Writer and Collections Examined
R. cataractae are widely known as stream riffle specialists (Facey and Grossman, 1992; Gibbons and Gee, 1972; Thompson et al., 2001; McPhail, 1997). Adult densities are highest in depths of 10 to 20 cm, at water velocities greater between 20 and 35 cm/s, over loose gravel, cobble or boulder substrates (Inglis et al., 1994; McPhail, 1997). Overwintering Nooksack adults have been found beneath cobble substrate in fast flowing riffles (Pearson, unpubl. data). Nooksack dace typically spawn at the upstream end of riffles and young-of-the-year occupy shallow (10-20 cm), calm, pools over fine substrates at the downstream end of riffles (McPhail, 1997).
The proportion of riffle habitat in a stream reach is the strongest predictor of Nooksack dace presence. They are rarely found in reaches with less than 10 percent riffle by length, or in reaches where long stretches of deep pool habitat separate riffles (Pearson, 2004). Natural habitat fragmentation occurs where low stream gradient precludes riffle formation and where beaver ponding converts riffles to pools. Anthropogenic fragmentation, caused by channel dredging and seasonal lack of flow due to ground and surface water extraction, is also common in the Canadian range.
In Canada Nooksack dace are associated with small to moderate-sized channels (1-10 m in width), but this probably reflects available habitat in occupied watersheds rather than a preference (McPhail, 1997). On the Olympic Peninsula mean channel width at occupied sites was 45.2 m (range 14.9-76 m, n=12, Mongillo and Hallock 1997).
Streams in the Fraser Delta area typically have small watersheds, minimal low flows in July and August, and limited natural or artificial storage; some have significant water demands. Storage development, riparian zone management, and erosion control are all important issues (Rood and Hamilton 1994).
The Brunette River is considered to have undergone significant alteration to its hydrological regime due to urbanization. In particular, the lower portion of the Brunette River is characterized by channelization and dyking, with no instream cover, high water temperatures and low dissolved oxygen (Rood and Hamiltion 1994).
The current extent of riffle habitats and occupancy in the Nooksack tributaries is well documented (Fig. 4; Pearson 1998a,b; Pearson 2004). The trend in its quantity and quality is clearly one of decline. At least some riffles in all three creeks are compacted by sediment from bank erosion and/or urban storm sewer effluent (Pearson, 2004). The mainstem of Fishtrap Creek was dredged for flood control by the City of Abbotsford in 1990-1991, eliminating most of its previously abundant riffle habitat (J.D. McPhail, pers. comm. 2006). In particularly dry years (e.g. 2002) flow ceases completely in some occupied reaches of Bertrand Creek, eliminating riffle habitat. Reaches with strongest baseflows still lose over 80% of riffle area relative to winter levels (Pearson, unpubl.). Aquifer draw-down by local wells is estimated to have reduced the creek’s baseflow by 24% since 1960 (Golder and Associates, 2004). Surface withdrawals for irrigation are also of water licences held in the Nooksack drainage is significant. These large-scale abstractions or diversions undoubtedly limit availability of nooksack dace habitat (riffles) in the low-flow summer months in some locations as all of these licences are run significant, but have not been quantified.
A number of river withdrawals occur during the dry periods for irrigation purposes. Bertrand, Fishtrap and Pepin creeks are all relatively small streams that begin to lose riffle habitat (width) when flows drop below 10% mean annual discharge (mad) and riffle quality (depth and velocity) when flows drop below 20% mad (mad; Ptolemy and Lewis 2003). In recent years (1984-2005), Betrand Creek in particular has seen 30-day summer flows as low as 1% mad (Ron Ptolemy, Standards and Guidelines Specialist, Ecosystems Branch, BC Ministry of Environment, Victoria, BC; personal communication 2007) Fishtrap Creek baseflows are also a concern with monitored flows averaging 10% mad and dropping to <1% mad in the 2003 drought. Pepin Creek flows in contrast are relatively healthy with baseflows averaging 24% mad and lows as >10% during drought periods (R. Ptolemy, pers. comm.).
Only crude estimates of habitat loss are possible, due to lack of baseline data (Table 3). They suggest that approximately half of the original riffle habitat from the Nooksack tributaries has been lost, most of it prior to 1996. Losses in the past 10 years appear to have been minimal, mostly due to beaver pond inundation of riffles in Pepin Creek (Pearson, 2004).
|Units||Pepin Creek||Fishtrap Creek||Bertrand Creek||Brunette River|
|Existing Area (from Table 1)||(m2)||2 000||2 300||3 000||20 155|
|Losses to 1996||(m2)|
|Losses since 1996||(m2)*||235||0||0||0|
Habitat was assumed to have comprised 20% of channel length in reaches known or believed to have lost substantial riffle area prior to 1996.
* measured by Pearson (2004)
** Areas calculated as product of mean wetted widths (from Pearson, 1998a) and 20% of reach length rounded to nearest 100 m2
There is no known Nooksack dace habitat on federal or provincial lands, but approximately 2 km of occupied habitat in the Nooksack River tributaries (Table 4) and at least 5.2 km of suitable or occupied habitat in the Brunette River (Pearson unpubl. data) occur on regional or municipal parkland. This amounts to somewhat more than 10% of suitable habitat.
Virtually all of the remaining habitat is on private, urban or agricultural lands. There is limited legislative protection at present. The ‘harmful alteration, disruption or destruction’ of fish habitat, including that of Nooksack dace, is partially prohibited by the federal Fisheries Act (R.S.C. 1985, c. F-14, s. 35-36). The Species at Risk Act prohibits the destruction of habitat identified as critical in an approved recovery strategy or action plan (SARA, S.C.2002, c.29, s. 57-58), but the competent minister must make an order before the prohibitions apply.
All occupied or potential habitats in the Nooksack River tributaries (Fig. 4) are proposed by the Recovery Team for designation as critical habitat under SARA.
|Watershed||Ownership||Description||Channel Length Present/ Suitable/ Occupied||Status/Comments|
|Pepin Creek||Greater Vancouver Regional District||Aldergrove Lake Regional Park||4825 m Pepin Brook and tributaries; 1660 m occupied||Regional parkland|
|Bertrand Creek||Township of Langley||Otter Park||225 m Bertrand Creek; 225 m occupied||Municipal parkland; Extremely vulnerable to drying|
|Federal Government Dept. Nat. Defence||Naval Station Aldergrove||2850 m Bertrand Creek; 0 suitable||Military lands; Extreme headwaters|
|Township of Langley||Vanetti Park||175 m Bertrand Creek; 0 suitable||Municipal parkland; Upstream of suitable habitat|
|Township of Langley||Creekside Park||185 m Bertrand Creek; 0 suitable||Municipal parkland|
|Fishtrap Creek||City of Abbotsford||Gardner Park, City of Abbotsford||260 m Enn’s Brook; 120 m suitable||Municipal parkland|
|City of Abbotsford||East Fishtrap Creek Park||1500 m East Fishtrap Creek; 0 suitable||Municipal parkland; Upstream of suitable habitat|
|Brunette River||Greater Vancouver Regional District||Burnaby Lake Regional Park||9000 m of mainstem and tributaries; 2450 msuitable||Regional parkland|
|City of Burnaby||Deer Lake Park||2400 m of Deer Lake and Creek; 515 m suitable||Municipal parkland|
|City of Burnaby||Hume Park||415 m Brunette River; 415 m occupied||Municipal parkland|
|City of Burnaby||East Lake Park||500 m Stoney Creek; 500 m suitable||Protected as municipal parkland|
|City of Burnaby||Stoney Creek Park, City of Burnaby||825 m Stoney Creek; 825 m suitable||Municipal parkland|
|Greater Vancouver Regional District||Burnaby Mountain Conservation Area||1565 m Stoney Creek; 500 m suitable||Regional park; Extreme headwaters|
Only 3.27 km of the 21.4 km marked consists of riffle and could actually be occupied (adapted from National Recovery Team for Salish Sucker and Nooksack Dace, 2005). Pepin Brook = Pepin Creek.
- Date Modified: