Recovery Strategy for Cultus Pygmy Sculpin
4. Habitat Trends
Current and historic data are lacking for quantity and quality of Cultus pygmy sculpin habitat, so specific trends in habitat availability are unknown. Comparisons of limnological information from 2001 with that collected in the 1930s and 1960s suggest that Cultus Lake limnetic habitat has changed little over the past 65 years, despite a considerable increase in public use of the lake and adjacent lands (COSEWIC 2003). Land use practices and other human activities have likely caused some decline in habitat quantity and quality, but the magnitude of change appears to be greatest in shallow littoral areas. The impact of these changes on Cultus pygmy sculpin is not known. Below we discuss general trends in land and water use in the watershed.
Cultus Lake has been a popular recreation destination dating back to the late 1800s. The watershed is heavily developed for recreation, residential and agricultural uses, and virtually all developable shoreline is developed to some extent (Ministry of Lands, Parks & Housing 1980). The remaining shoreline is steep-sided and inaccessible by road. Cultus Lake Provincial Park was formed in 1948, and today contains 656 ha on both east and west shores of Cultus Lake. In 1969, International Ridge Recreation Area was established, totalling 2080 ha encompassing all of the land between the eastern boundary of the park and the height of land. Cultus Lake Municipal Park is located on the north shore of the lake and covers about 259 ha. The park was formed under provincial statute in 1932 and is owned and operated by the City of Chilliwack.
Cultus Lake Provincial Park is the most popular destination area in the Lower Mainland and ranks either second or third in the province for total campground visitation, depending on the weather during a given summer (Ministry of Lands, Parks & Housing 1980). Park use is heavy and sustained throughout the summer, resulting in capacity crowds each weekend and on most midweek days during fine weather (Ministry of Lands, Parks & Housing 1980). Historic park use has been proportional to population growth in the region, with approximately 1.5 million park visitors per year at present (COSEWIC 2003). Both parks are operated for intensive water and beach activities. The foreshore and upland areas of the park continue to be developed, primarily for recreation and tourism (Ministry of Lands, Parks & Housing 1980; Cultus Lake Parks Board 2006).
Activities such as hunting and forest harvest are permissible within the Recreation Area, but logging is unlikely throughout much of the watershed due to steep and unstable soils (Ministry of Lands, Parks & Housing 1980). Present forest cover on the east side of the lake is predominantly second growth Douglas fir and maple, a result of logging prior to park status. At present, logging occurs only in the headwaters of Frosst Creek in the United States (COSEWIC 2003). The impacts to Cultus Lake from forest harvesting are probably minor (COSEWIC 2003).
Permanent housing is restricted to small areas on the northeast and northwest sides of the lake and at Lindell Beach at the south. Farming occurs near the south end. Activities with direct impacts to the lake’s littoral zone include the removal of aquatic and riparian vegetation, shoreline alteration and physical encroachment by wharves and piers (COSEWIC 2003). Activities that impact tributary streams include channelization and the removal of riparian vegetation (COSEWIC 2003). Of special concern is the potential degradation of the quality of the lake’s surface and ground water inputs as a result of seepage from septic systems, agricultural runoff and the domestic use of fertilizers (COSEWIC 2003).
The biggest observable change in lake habitat occurred following the introduction of Eurasian milfoil (Myriophyllum spicatum) in the late 1970s. From 1977 to 1991, its distribution in the littoral zone nearly doubled and shifted from mainly sparse patches to dense mats (COSEWIC 2003). By 1991, it covered 22 ha of the lake’s 74 ha littoral area (Truelson 1992); subsequent distributions have not been monitored. It is not known if Cultus pygmy sculpin historically used littoral areas now infested with milfoil.
5. Habitat Protection
There are no habitat protection provisions specifically for Cultus pygmy sculpin, however, the species likely benefits from existing legislation (Fisheries Act) that protects fish habitat generally. Approximately 92% of the shoreline of Cultus Lake is within Cultus Lake Provincial Park and Cultus Lake Municipal Park. These parks extend to upland areas (Figure 2).
6. Critical Habitat
Identification and protection of critical habitat is vital for management of species at risk. While defining critical habitat is one of the most challenging aspects of species management, it is vital to ensuring a species’ long-term survival. This rationale is central to endangered species legislation in general, and specifically to the Species at Risk Act (SARA), where critical habitat is defined 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)]
The need to designate and protect critical habitat is clearly recognized by scientists, resource managers, and the general public. Despite its complexity, the core issue is the same for all species: to determine the role of habitat in population limitation, and to answer the question, How much habitat is necessary for the survival and recovery of a listed wildlife species?
6.1 Identification of the Species’ Critical Habitat
At this point, it is possible to indicate general habitat features that are likely important. For example, if it is true that Cultus pygmy sculpin nest in the deep benthic areas of Cultus Lake, some or all of this habitat could qualify as critical. Cultus pygmy sculpin use the limnetic areas of the lake during the majority of their life and likewise some or all of this habitat could qualify as critical. Clearly, these habitats, or portions of them, will feature in the definition of the species’ critical habitat. However, due to a number of information gaps, we are unable to provide a defensible demarcation of critical habitat at this time. General knowledge gaps are discussed in Section 13.
6.2 Schedule of Studies
Very little is known about Cultus pygmy sculpin. The following schedule of studies should allow delineation of critical habitat for Cultus pygmy sculpin. A more detailed description of each task will be developed in one or more Action Plans. These studies are projected to be undertaken in the next five years, and reassessed in conjunction with updates to the recovery strategy.
Habitat Use.-- The first task is to develop a better understanding of habitat use by different life stages of Cultus pygmy sculpin. A description of the basic habitat associations for each life stage is a core information need for defining critical habitat (Rosenfeld and Hatfield 2006), in particular spawning habitat of Cultus pygmy sculpin. There is a general understanding of habitat types used by Cultus pygmy sculpin, but a more precise understanding is essential. Where possible, habitat requirements will be defined in terms of microhabitat components such as depth, substrate type and condition, physical water characteristics, etc.
Habitat Availability.-- The second task is to review historic and current habitat availability. Information on the extent and distribution of different habitat types available to a species is also a key component of critical habitat delineation. Studies are required that describe abundance and distribution of different habitats in the wild. Where possible, historic habitat availability should be explored to help provide context for the present condition and the final delineation of critical habitat.
Population Abundance.-- Clearly defined population recovery targets for each life stage are integral to the identification of critical habitat because the quantity of habitat designated as critical must be related to a population benchmark (Rosenfeld and Hatfield 2006). This task is to review historic and current population abundance, as part of the process of setting recovery targets. Both the current and historic population abundance provide meaningful context for the recovery target, though we recognize that historic abundance may be difficult to ascertain with accuracy. It may only be possible to qualitatively assess historic abundance of Cultus pygmy sculpin.
Recovery Targets.-- Setting recovery targets may require several steps and the collection of several pieces of information. Recovery targets may be based on rules of thumb (e.g., Thomas 1990; IUCN 2001; Reed et al. 2003), numeric analyses such as population viability analysis (PVA; Morris and Doak 2002), or a combination of techniques. For organisms such as Cultus pygmy sculpin, where relatively little information exists and additional information takes a long time to collect, it may be beneficial to use targets based on rules of thumb. However, it is nevertheless valuable to examine such targets by assessing key population parameters (e.g., survival and fecundity) and to undertake specific population modeling (e.g., elasticity analysis, see Gross et al. 2002) to explore which life stages are most limiting to sculpin abundance. It will be necessary to set targets for each major life stage (Rosenfeld and Hatfield 2006).
Relationship Between Habitat and Abundance.-- Designation of critical habitat requires quantitative relationships between habitat and abundance because these relationships are needed to establish the amount of habitat required to achieve a population recovery target (Rosenfeld and Hatfield 2006). Developing such a relationship is not a straightforward task and may need to rely, at least in part, on expert judgement.
Define Critical Habitat.-- The final step in delineating critical habitat is to use population targets and relationships between habitat types and abundance to determine how much of the different habitats are required to maintain a viable population of Cultus pygmy sculpin, and to then identify the specific locations of these habitats in the wild.
6.3 Examples of Activities That Are Likely to Result in Destruction of Critical Habitat
Until critical habitat is formally delineated it is not possible to provide specific guidance on which activities are most likely to destroy critical habitat, other than in very general terms. For example, activities that threaten deep littoral areas or those that alter the productivity of limnetic areas may have negative impacts on Cultus pygmy sculpin. The more general threats to some of the important habitat types for Cultus pygmy sculpin are discussed in Section 3.
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