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Recovery Strategy for the Rocky Mountain Sculpin (Cottus sp.), Eastslope populations, in Canada

7. Critical habitat

7.1 General identification of the Rocky Mountain sculpin’s critical habitat

Critical habitat is defined in the Species at Risk Act (SARA) (2002) section 2(1) as:

“…the habitat that is necessary for the survival or recovery of a listed wildlife species and that is identified as the species’ critical habitat in a recovery strategy or in an action plan for the species.” [s. 2(1)]

SARA defines habitat for aquatic species at risk as:

“… spawning grounds and nursery, rearing, food supply, migration and any other areas on which aquatic species depend directly or indirectly in order to carry out their life processes, or areas where aquatic species formerly occurred and have the potential to be reintroduced.” [s. 2(1)]

Critical habitat for the Rocky Mountain Sculpin is identified to the extent possible, using the best information currently available. Section 58 ensures that the critical habitat of listed species at risk is legally protected either by way of a prohibition, under SARA, against the destruction of critical habitat, or by provisions in, or measures under, SARA or other Acts of Parliament.

Critical habitat identified in this recovery strategy describes the geospatial area and the biophysical features which support functions necessary to support the survival and or recovery of the species. The schedule of studies outlines the activities required to refine areas of critical habitat and further describe the features, functions and attributes of those habitats to support its protection.


7.1.1 Information and methods used to identify critical habitat

Using the best available information, critical habitat has been identified in Lee Creek as well as in the St. Mary, North Milk, and Milk rivers using a slightly modified ‘bounding box’ approach. This approach assumes that there is a thorough understanding of the features functions and attributes of the habitats associated with all life stages of the sculpin but the actual locations of these habitats are not known. In the case of the Rocky Mountain Sculpin there is fairly uniform distribution of individuals at different life stages in certain habitats, particularly in the North Milk and St Mary rivers. The features functions and attributes of those habitats in which Rocky Mountain Sculpin generally occur may be described in detail; essentially, most if not all life stages of Rocky Mountain Sculpin occur in riffle and run type habitats as defined in Table 14. Considering the above, the approach to identifying critical habitat for the sculpin was further modified by catch per unit effort (CPUE) as well as ecological classification. CPUE was used to help identify critical habitat limitations in the St. Mary River and Lee Creek. In the North Milk and Milk rivers, critical habitat was identified using CPUE and ecological features and attributes. Life stage habitat information is described in sections section3.4.1 (Biology and Life History) and section3.4.2 (Habitat). The bounding box approach was the most appropriate, given the limited information available for the species and the lack of detailed habitat mapping for these areas.

The areas identified can be refined and/or additional areas could be also identified if new information comes to light regarding the life history needs of the Rocky Mountain Sculpin. Areas of critical habitat identified at some locations may overlap with critical habitat identified for other co-occurring species at risk; however, the specific habitat requirements within these areas may vary by species.

St. Mary River:

Comparable backpack electrofishing CPUE data was collected for the St. Mary River from the U.S. Border to the Highway 5 crossing on the St. Mary River. The species is common and abundant throughout this stretch of the St. Mary River with an average density of 0.75 fish/m2 at flows <20 m3/s (D. Watkinson, unpubl. data).

Lee Creek:

CPUE declines quickly moving upstream from the confluence of Lee Creek with the St. Mary River. The CPUE is highest in the lower 13 km of the creek (>0.01 fish/sec of backpack electrofishing). Limited sampling has been conducted upstream and CPUE was <0.01 fish/sec of backpack electrofishing.

North Milk and Milk Rivers:

Boat electrofishing has provided CPUE data from Canadian reaches of the Milk River downstream from its confluence with the North Milk River. While the number of sites sampled by backpack electrofishing on the North Milk River is low, the CPUE at these sites has been high from the U.S. Border to the confluence with the Milk River (river km 238). In the Milk River, the area of occurrence extends from the U.S. Border downstream into R1. The CPUE is low in the Milk River upstream of its confluence with the North Milk River. This habitat is considered marginal as surface flow often stops during the summer. While the species has been caught downstream of the R3/R2 reach break (river km 162), it was absent from the boat electrofishing catches in these reaches which provides standardized sampling for comparisons. This abrupt decline in CPUE corresponds with a change in habitat to predominately silt and sand substrates (≥70%). The habitat in reaches R2 and R1 is not preferred for sculpin, although pockets of suitable habitat may exist.

The approach used to identify critical habitat for the Rocky Mountain Sculpin is independent of a specific population recovery target. Population numbers and habitat do no appear to require recovery or restoration. Recovery planning should focus on protecting and maintaining existing Rocky Mountain Sculpin populations and their habitats.


7.1.2 Identification of critical habitat: geospatial

Critical habitat for Rocky Mountain Sculpin in Alberta is defined as all of the St. Mary River from the U.S. Border to the St. Mary Reservoir (upstream 49.0000 degrees North – 113.32870 degrees West to 49.24966 degrees West – 113.25595 degrees West), the lower 13 km of Lee Creek (upstream 49.16847 degrees North to confluence of St Mary River). Further sampling is needed to refine the upstream extent of critical habitat in Lee Creek. The North Milk and Milk rivers from the U.S. Border to the confluence of mainstem Milk River, and the mainstem Milk River from the confluence with the North Milk River downstream to the R3/R2 reach boundary are also considered critical habitat for Rocky Mountain Sculpin (upstream 49.00000 degrees North – 112.99867 degrees West to 49.10961 degrees North – 111.85008 degrees West). The Milk River upstream of the confluence with the North Milk River was not considered critical habitat as surface flows are periodically absent; likewise, the predominance of fine substrates downstream from the R2/R3 reach break makes those habitats marginal for Rocky Mountain Sculpin. To provide a buffer zone, the bankfull channel is considered part of the critical habitat. The locations of critical habitat are shown in Figure 5. These are areas that the Minister of Fisheries and Oceans considers necessary to support the species’ survival or recovery objectives.

Critical habitat is not comprised of all the area within the identified geographic boundaries but only those areas where the specified biophysical features occur. Permanent anthropogenic features such as marinas, road crossings, infiltration galleries, outfalls, canals etc. that require routine maintenance and are within the areas delineated as critical habitat are excluded and not considered to be critical habitat for the Rocky Mountain Sculpin.


Figure 5. Critical habitat for the Rocky Mountain Sculpin in Alberta.

Map showing species occurrence (see long description below).

Description of Figure 5

Figure 5 is the same map from Figure 3 showing species occurrence, sampling locations and habitat features. This map also shows a wide band that encompasses the entire river width representing critical habitat. The band covers a portion of the upper St Mary River and the mid to upper portion of the Milk River.


7.1.3 Identification of critical habitat: biophysical functions features and their attributes

Information on some key aspects of the life history and biology of the Rocky Mountain Sculpin is limited. Table 14 summarizes available knowledge on the essential functions, features and attributes for each life-stage. Refer to Section 3.4.1 (Biology and Life History) for full references. Areas identified as critical habitat must support these features.

Table 14. General description of essential functions, features and attributes of critical habitat for each life stage of the Rocky Mountain Sculpin
Life StageHabitat Requirement (Function)Feature(s)Attribute(s)
Larvae to Young of the Year (Age 0+)
  • Rearing/Nursery
  • Riffle and runs
  • Depth 10-75 cm
  • Velocity 0.1-0.5 m/s
  • Substrate, gravel
  • Temperature ranging 7.8-17.2°C.
Juvenile (Age 1-3)
  • Feeding and cover
  • Riffles and runs
  • Depth 20-80 cm
  • Velocity 0.5-1.1 m/s
  • Substrate, gravel, and cobble
Adult (Age 3+)
  • Spawning (mid May to June)
  • Riffle and runs
  • Temperatures between 7.5 and 12.8 °C.
  • Substrate cobble to boulder
  • Aquatic vegetation, large woody debris)
Adult (Age 3+)
  • Feeding and cover
 
  • Depth 25-80 cm
  • Velocity 0.6-1.1 m/s
  • Substrate, gravel, and cobble


Habitat that falls outside the definition above may also be recommended as critical in subsequent action plans if it is known to provide a critical function as per the description of habitat in SARA. The ranges of attributes in table 14. are optimal for the Rocky Mountain Sculpin. The species is not limited to these areas and may and are known to occur outside of these areas throughout their distribution.

Studies to further refine knowledge on the essential functions, features and attributes for various life-stages of the Rocky Mountain Sculpin are described in section 7.2 (Schedule of studies to identify critical habitat).

7.2 Schedule of studies to identify critical habitat

This recovery strategy includes an identification of critical habitat to the extent possible, based on the best available information. Further studies are required to identify and/or refine additional critical habitat necessary to support the population and distribution objectives for the species as per Table 15 below.

Table 15. Schedule of Studies to identify or refine critical habitat
Description of StudyRationaleTimeline
Conduct studies to identify and characterize habitat use by life stage of Rocky Mountain Sculpin.There is limited information known about the reproductive strategy of adults or specific habitat needs for early life-stages.

This work will help refine critical habitat and will specifically link habitat use to life stage.
2012-2015
Movement studiesThe seasonal movements and area required by individual fish are unknown.

These studies will determine the extent of movement for this species, particularly for spawning and overwintering purposes and the potential to re-colonize habitat. They may also help refine areas of critical habitat by clearly identifying distribution
2012-2015


These studies are designed to provide a more complete picture of the critical habitat requirements of the Rocky Mountain Sculpin. A precautionary approach to the identification of critical habitats was utilized to help meet the population and distribution objective until a more comprehensive analysis has been completed. The prescribed schedule of studies is, of necessity, a long term planning document and will be revised periodically or refined on an ongoing basis as further information warrants.

7.3 Examples of activities likely to result in the destruction of critical habitat

The definition of destruction is interpreted in the following manner:

Destruction of critical habitat would result if any part of the critical habitat were degraded, either permanently or temporarily, such that it would not serve its function when needed by the species. Destruction may result from single or multiple activities at one point in time or from cumulative effects of one or more activities over time.”

Under SARA, critical habitat must be legally protected from destruction once it is identified. This will be accomplished through a s.58 Order, which will prohibit the destruction of the identified critical habitat.

The activities described in the table below are neither exhaustive nor exclusive and have been guided by the General Threats described in section 4.1 of the recovery strategy for the species. The absence of a specific human activity does not preclude, or fetter the department’s ability to regulate potential impacts pursuant to SARA. Furthermore, the inclusion of an activity does not result in its automatic prohibition since it is destruction of critical habitat that is prohibited not the activity. Since habitat use is often temporal in nature, particularly in fluvial systems like southern Alberta, the potential of destruction of critical habitat is assessed on a case-by-case basis and site-specific mitigation is applied. In every case where projects are proposed in areas of critical habitat, sufficient lead time and baseline information will be necessary to better inform management and regulatory decision-making.

Table 16. Examples of activities likely to result in the destruction of critical habitat for the Rocky Mountain Sculpin
ThreatActivityAffect –PathwayFunction AffectedFeature AffectedAttribute Affected
Habitat Loss or DegradationDam Construction (water impoundment or reservoir creation)Large-scale loss of habitat (change from riverine to reservoir)
  • Spawning
  • Rearing/nursery
  • Feeding and cover
  • Riffles and runs
  • Depth
  • Velocity
  • Substrate
  • Temperature
Habitat Loss or DegradationDam Operation (flow modification)Reduction in available habitats
  • Spawning
  • Rearing/nursery
  • Feeding and cover
  • Riffle and runs
  • Depth
  • Velocity
  • Substrate
  • Temperature
Habitat Loss or DegradationWater withdrawalReduction in available habitats
  • Spawning
  • Rearing/nursery
  • Feeding and cover
  • Riffles and runs
  • Depth
  • Velocity
  • Temperature
Point Source PollutionRelease of harmful substancesReduction in available habitat (e.g. loss of interstitial spaces)
  • Rearing/nursery
  • Feeding and cover
  • Rifles and runs
  • Substrate
  • Temperature