Nooksack Dace (Rhinichthys cataractae ssp.): residence description

1 Introduction

SARA states that

“No person shall damage or destroy the residence of one or more individuals of a wildlife species that is listed as an endangered species or a threatened species, or that is listed as an extirpated species if a recovery strategy has recommended the reintroduction of the species into the wild in Canada.” [section 33]

Also, SARA defines “residence” as:

“a dwelling-place, such as a den, nest or other similar area or place, that is occupied or habitually occupied by one or more individuals during all or part of their life cycles, including breeding, rearing, staging, wintering, feeding or hibernating.” [subsection 2(1)]

Sections 2 and 3 below provide a description of a residence for Nooksack Dace. The information in these sections was adapted from the “Recovery Strategy for the Nooksack Dace (Rhinichthys cataractae ssp.) in Canada” (DFO 2020). The geographic distribution of the Nooksack Dace is described in the recovery strategy for this species (DFO 2020).

2 Structure, form and investment

Nooksack Dace (Rhinichthys cataractae ssp.) spawn at night during the spring and usually at the upstream end of riffles (McPhail 1997). They establish small breeding territories (a 10 cm diameter nest) in coarse substrate (Bartnik 1972). A 2015 survey of Bertrand Creek revealed newly emerged fry at virtually all riffles in the watershed (Pearson 2016). All riffles within critical habitat and occupied areas should be regarded as containing residences during spawning and incubation season (mid-April to mid-August).

The nest site is a 10 cm diameter depression in the gravel cleaned and formed by probing with the snout. Nests are constructed by males prior to courtship, and by both sexes during courtship. A study of the Nooksack-Columbia Dace hybrids of the Alouette River documented male defence of territories against all fish except receptive female dace. Males entice females to spawn in their territory using complex courtship cues (Bartnik 1972). Females do not deposit all of their eggs in a single spawning event or remain in the nest after spawning; they usually deposit eggs in multiple nests (Bartnik 1973; McPhail 2007).

3 Occupancy and life-cycle function

Nests are occupied by eggs during incubation and are occupied and defended by males during nest preparation, courtship, and egg incubation (Bartnik 1973). Incubation averages one week, but varies with water temperature. Hatching is a protracted process, requiring at least 2 days at 18°C (McPhail 2007). At least two pulses of spawning have been detected in populations in the Columbia system and in North Carolina (Roberts and Grossman 2001; McPhail 2007) and female Nooksack Dace in spawning condition have been captured in Canada between the end of April and the beginning of July (M. Pearson pers. comm. 2017). Egg incubation and emergence of fry is likely complete by mid-August. Typically all riffles in occupied reaches support spawning and incubation (Pearson 2016) and should be assumed to contain residences between mid-April and mid-August (Pearson 2004).

4 References