Morrison creek lamprey (Lampetra richardsoni var. marifuga) recovery strategy: chapter 3
Description of Needs of the Species
2. Description of Needs of the Species
2.1 Ecological Role and Limiting Factors
Ecological Role.-- After metamorphosis L. richardsoni var. marifuga are assumed to be external parasites of other fish species, though this has not been directly observed in the wild. If true, Morrison Creek lamprey plays a role in limiting abundance of its prey species. Clearly more studies are required to assess the effect on prey abundance and distribution. It is possible that lamprey also feed on salmon carcasses (R. Beamish, pers. comm.). Lamprey are themselves preyed upon by fishes and other wildlife and thereby form part of the food base of those species. Ammocoetes are most vulnerable to predation immediately after emerging from their burrows (Close et al. 2002). Both live and spawned out adults of Pacific Lamprey are a significant component of some fish and wildlife diets (Close et al. 2002), though the extent of predation on Morrison Creek lamprey is not known.
Limiting Factors.-- The environmental factors that limit Morrison Creek lamprey have not been well-studied. We assume that populations are affected by competition, predation, habitat quantity and quality, and food availability though the relative effect of each is not known. It is evident that to persist over the long term, all species require sufficient rearing and spawning habitat and a healthy food base.
2.2 Habitat Needs
L. richardsoni var. marifuga is found only in Morrison Creek, a tributary of the Puntledge River on Vancouver Island (Figure 4). The Morrison Creek watershed is in the coastal Douglas fir biogeoclimatic zone. The area experiences a variable climate that is generally warm and dry in summer and mild and wet in winter. A variety of fish species are present in Morrison Creek (Province of BC 2005), including pink (Oncorhynchus gorbuscha), coho (O. kisutch), chinook (O. tsawytscha) and chum salmon (O. keta), resident and anadromous cutthroat trout (O. clarki), rainbow and steelhead trout (O. mykiss), Dolly Varden char (Salvelinus malma), three types of lamprey (Pacific lamprey, Lampetra tridentata; Morrison Creek lamprey, L. richardsoni; and L. richardsoni var. marifuga).
The Morrison Creek watershed is 890 ha in size (Ellefson 2003) and provides year-round fish habitat. The creek is characterized by cool, clean, year-round flows that originate from spring sources in the headwaters (Ellefson 2003). There are multiple wetlands in the upper watershed, which likely attenuate flow and temperature fluctuations throughout the year. The upper watershed is about 543 ha in size, of which over 96 ha is wetland (Ellefson 2003). The headwaters are defined at their upper reaches by an approximately 30 m scarp composed of glacial till (largely gravel and sand), with a series of spring-fed wetlands and creeks at the base of this escarpment. A key difference between Morrison Creek and other creeks on the east coast of Vancouver Island is the volume of water stored in the headwaters. The area is a complex of beaver dams and natural berms that store water and release it slowly through the dry summer months. The relatively high fish production of Morrison Creek is believed to be related to the year-round cold water, which is available in fairly high volume. It is not known whether conditions specific to Morrison Creek have allowed L. richardsoni var. marifuga to evolve and endure only here.
Spawning habitat requirements of Morrison Creek lamprey are not known in detail, but are assumed to be similar to those of Western Brook lamprey, which construct nests in areas of gravel, where eggs are deposited and fertilized, and subsequently rear to hatching. Hatching generally occurs a short time after fertilization. Clean gravels with some water flow is assumed to be required for spawning and incubation of Morrison Creek lamprey, as it is for other lamprey species. Although the nest is not long-lived, suitable habitat may be subject to impacts (e.g., sedimentation) even at times of years when it is not occupied. The distribution and utilization of suitable spawning habitats within Morrison Creek is not known. Since natural spawning of the marifuga variety has not been observed, greater detail cannot be provided at this time.
After hatching, lamprey ammocoetes drift a short distance from the nest, where they burrow into soft fine sediments or sand (Scott and Crossman 1973) and remain relatively sedentary for the duration of the larval phase, which can be an extended period (up to 7 years). Ammocoetes of L. richardsoni var. marifuga cannot be readily distinguished from those of “normal” L. richardsoni, but we assume that habitat needs for this life stage are similar for both forms. Larval habitat is thus defined generally as fine sediment areas in close proximity to spawning beds. The distribution of suitable rearing habitat and the distribution of ammocoetes within this habitat is not known for Morrison Creek.
Habitat requirements of other life stages of the marifuga variety are not known.
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