Science Advisory Report 2017/016
Review of the Information for the Identification of Critical Habitat for the Cowichan (Vancouver) Lamprey
Summary
- Entosphenus macrostomus (Cowichan Lamprey) has only been identified in Cowichan, Mesachie and Bear lakes. They have not been identified in the Cowichan River although no barrier exists preventing their movement into the river.
- Cowichan Lamprey was described as a distinct species in 1982. Since then, limited research has been conducted on its biology, ecological role, and habitat requirements.
- No recent reliable quantitative population estimates exist for Cowichan Lamprey. The population was estimated to be about 1,000 to 2,000 adults in 1988 and based on limited trapping studies in Mesachie Lake in recent years it is thought that the population may have declined since that time. In addition, reports of scars and wounds on salmon in the lake has varied over this period and may suggest fluctuations in the lamprey population. However using scars as an index of abundance is problematic as the information is opportunistic and dependent on reporting by fishermen.
- Habitat requirements vary depending on the life stage of lamprey. The lakes are required for feeding adults. Spawning adults use the nearshore habitat and fluvial fan regions of tributaries entering the lakes. The presence of ammocoetes in the lower portions of these tributaries suggests that some spawning may also occur in these stream regions. Habitat for burrowing ammocoetes requires medium-fine to fine substrates with a layer of organic debris.
- During spawning, lamprey build nests which could be considered residences as they are discrete dwelling places. Adults of both sexes invest energy, physically moving pebbles with their oral discs to create the nests; the nests support the life-cycle process of spawning and egg incubation and are occupied by multiple individuals for a period of time.
- The primary activities likely to destroy Critical Habitat include, but are not limited to: land-based activities that have the capacity to directly or indirectly alter their aquatic habitat including forestry, mining, and land development; water withdrawals or impoundments that alter the natural variability in water flow; releases of deleterious substances into the watershed; riparian vegetation removal; activities that result in significant sediment inputs; and overfishing of prey species.
- The high uncertainty of a number of factors related to Cowichan Lamprey make the identification of Critical Habitat difficult. These factors include, but are not limited to: the type of vegetation required to maintain the functions of the riparian zone; the quality of sites suitable for spawning; the location of spawning sites; distribution and habitat associations of ammocoetes in the lake; and abundance and type of prey species. Therefore, further work is suggested to provide quantitative and qualitative thresholds for Critical Habitat attributes.
- It is recommended that the critical habitat for the Cowichan Lamprey include Cowichan, Bear and Mesachie lakes in their entirety, the adjoining waterways and 100 metres upstream of tributaries into the lakes.
This Science Advisory Report is from the October 30, 2013 Review of the Information for the Identification of Critical Habitat for Cowichan (Vancouver) Lamprey. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.
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