Rainbow Trout (Oncorhynchus mykiss): 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 Rainbow Trout (Athabasca River populations). The information in these sections was adapted from the “Recovery Strategy for the Rainbow Trout (Oncorhynchus mykiss) in Canada (Athabasca River populations)” (DFO 2020). The geographic distribution of the Athabasca Rainbow Trout is described in the recovery strategy for this species (DFO 2020).

2 Structure, form and investment

Redds are created by female Athabasca Rainbow Trout (Oncorhynchus mykiss) for spawning and the initial development of eggs and alevins. Athabasca Rainbow Trout redds meet the SARA definition of residence. As spawning gravel moves from year to year, residence locations are temporary. Females select spawning sites in areas with subgravel flow. Prior to spawning, the female excavates a nest by turning on her side and forcefully moving her caudal fin, causing gravel to be moved downstream by the current. A few larger stones are usually kept and used to form a pocket to hold the eggs. The female then moves immediately upstream and begins excavating another nest, covering the fertilized eggs in the previous nest. The female may excavate three to four nests sequentially, forming a redd. The eggs, and later the alevin, remain in the nest until emergence from the gravel (Alberta Athabasca Rainbow Trout Recovery Team 2014, DFO 2018).

Redds created and used by Athabasca Rainbow Trout for spawning demonstrate there is significant investment in the creation and to some extent, in the protection of the residence (the act of filling with gravel) by Athabasca Rainbow Trout. Thus, a redd is considered to be the residence of this fish. The residence is limited to the redd itself and the spawning and incubation time period during which eggs and alevins are present in the redd.

3 Occupancy and life-cycle function

Spawning habitat for Athabasca Rainbow Trout is characterized by clean, small to medium gravel beds, which are generally found upstream of riffle crests in small to medium perennial streams. Fry emerge from the redd in flowing water and establish territories in shallow water along stream margins (COSEWIC 2014).

4 References