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Recovery Strategy for the Morrison Creek Lamprey (Lampetra richardsoni var. marifuga) in Canada (Final)


3. Threats

Given their extremely restricted distribution, Morrison Creek lamprey can be considered vulnerable to a variety of threats. Much information is lacking on the general biology of the variety, which makes a thorough threats assessment difficult. Nevertheless, it is possible to identify general threats, and these are discussed below.

Land Use.-- Some land-based activities have the capacity to alter aquatic habitat directly (e.g., impacts to riparian habitat, alteration of run-off rates or water storage capacity in headwaters) or indirectly (e.g., changes to water quality through introduction of pollutants). These activities include forestry, mining, and land development for residential or industrial uses. The primary concern at present in the Morrison Creek watershed is forest harvest and urban development. Historically, forestry has been the primary concern, and the Inland Island Highway, which cuts through a broad section of the upper watershed, may also have had impact. However, with the expansion of the Village of Cumberland into the upper Morrison Creek watershed, urban development appears to now exceed other land use issues as the main threat.

Development pressures are increasing in the Morrison Creek area, and have increased especially in the last several years. Alteration of land cover through building and road development generally changes many aspects of water quality and patterns of stream flow (Chilibeck et al. 1992). Morrison Creek may be somewhat buffered from impacts to streamflow given it is fed so consistently by springs and groundwater. However, there are still a series of threats associated with urban development that remain a concern (Chilibeck et al. 1992). Assessing this threat will require additional information on distribution and utilization of spawning and rearing habitats for Morrison Creek lamprey, and identification of key areas in the watershed that are key to maintaining the natural flow regime.

Forest harvesting has been and continues to be a prominent activity in the headwaters of Morrison Creek, but impacts associated with it are likely decreasing as forestry activity declines in the watershed. Remaining threats may, however, be more difficult to regulate as much of the watershed is private land and therefore not subject to the provisions of the Forest and Range Practices Act (BC). The primary potential threats to aquatic habitat from forestry practises include sedimentation, riparian habitat destruction, and changes in water quality. There is a broad literature demonstrating the negative effects of suspended sediments on fish and egg survival. Moderate increases in fine sediment inputs associated with logging may be a benefit for lamprey ammocoetes in sediment-poor drainages, because ammocoetes rear in depositional habitats with fine sediments, conditions that are often lacking in high gradient coastal watersheds (Beamish 1998). Excessive sediments inputs, however, may negatively impact spawning habitat and perhaps other lamprey habitats. Sediment is unlikely to be a limiting factor for lamprey in the Morrison Creek watershed, which is relatively low gradient and has an abundance of glacially-derived substrate.

Water Use.-- Most residents in the Morrison Creek watershed receive water from the Regional District system, which draws from Comox Lake (J. Palmer, pers. comm.). The exceptions are a small number of properties on wells and the Puntledge Townsite (also known as “Bevan”), which pipes from the springs feeding Supply Creek, a tributary of Morrison Creek. This source supplies 10 homes and, for part of the year, a small volunteer salmon hatchery (water licensee: Courtenay and District Fish and Game Protection Association).

A water licence query (Land and Water BC 2005) lists 8 water licences on Morrison Creek and 12 on Supply Spring. The licences on Morrison Creek sum to 8515 • yr-1, but several do not specify an instantaneous limit to diversion. Licences on Supply Spring sum to 143,907 • yr-1, with about 93% of this allocated to the fish hatchery. Actual consumption patterns are not known (Kreye et al. 1996), so it is not possible to assess the effect of water diversions on stream flows. The future demand for water is difficult to predict, but since the main source of water for residential use is Comox Lake, it is possible that future demands for Morrison Creek water will not increase substantially.

In addition to licensed users there are likely unlicensed water users in the Morrison Creek watershed. The threats to Morrison Creek lamprey posed by unlicensed water users is not known, but seems unlikely to exceed the threats posed by licensed users.

Water Quality.-- Water quality issues have not been raised as a severe threat to this point, although there are several concerns. Contaminated groundwater from the Pidgeon Lake landfill discharges into Morrison Creek and Nellie Creek to the northeast, and Comox Lake to the west. Potential impacts on water quality associated with this pollutant source have not been evaluated. The boundary expansion of the Village of Cumberland into the upper Morrison Creek watershed will likely be followed by increased urbanization. Run-off from additional developed area is likely to lead to water quality declines in the stream, as water comes into contact with roads, buildings, lawns and other urban surfaces. This threat may require additional assessment in the future as related information becomes available.

Prey Base.-- Based on lab studies, adult L. richardsoni var. marifuga are believed to be external parasites of other fish species, although feeding behaviour has not been observed in the field (Beamish 1985; Beamish et al. 1999). Human impacts on prey species (e.g., recreational and commercial fishing, habitat degradation and destruction) are therefore expected to directly affect abundance of Morrison Creek lamprey. Ammocoetes are filter feeders, feeding on detritus and suspended organic matter while living in burrows in soft sediments. Activities that alter the productivity of this food base are expected to also affect abundance of Morrison Creek lamprey. There have been no quantitative assessments of the threats to the prey base of Morrison Creek lamprey, but Ellefson (2003) lists a number of concerns associated with forest harvest and urban development in the Morrison Creek watershed and their effect on fish and fish habitat.

Non-native species pose a possible though unquantified threat to Morrison Creek lamprey. Several predatory aquatic species, including brook trout (Salvelinus fontinalis), brown trout,(Salmo trutta), bass (Micropterus spp.), pumpkinseed sunfish (Lepomis gibbosus), yellow perch (Perca flavescens), brown catfish (Ameiurus nebulosus) and the bullfrog (Rana catesbeiana) have been introduced to Vancouver Island and are spreading throughout the region. These and other introductions may pose a threat via direct predation on ammocoetes and adults, or through changes in the prey base of lamprey and the overall ecological community. At present this threat is deemed to be minor, but may increase in the future.

Climate Change.-- Scientific evidence clearly indicates that climate is changing and animal and plant distributions are responding to these changes (Parmesan and Yohe 2003). Since climate affects precipitation, water flow and temperature in many ways, it may also affect Morrison Creek lamprey abundance and distribution. This threat is of concern; however, it presents a less immediate risk to the lamprey population than other threats, and at present the topic is considered beyond the scope of this recovery strategy. The threat may be assessed and addressed at future stages of recovery planning for Morrison Creek lamprey. Ensuring the stability of groundwater and headwater flows to the system is probably the most effective way to buffer against impacts associated with climate change. The existence of significant groundwater inputs to baseflow in Morrison Creek indicates that it may be more resilient to climatically-driven increases in air temperature than other systems on the east coast of Vancouver Island, so that the watershed may become a potential refuge for coldwater species in the future.

Research.-- Scientific study itself may have an impact on this form, although the magnitude of effect is not known. Specific activities that may impact the population status include electrofishing for salmonid assessments (this may especially affect ammocoetes), installation and operation of salmonid fish-counting fences (this may hinder migration of adult lamprey), and capture of individuals for study (this may affect lamprey population status if the take rate is high relative to abundance and reproductive rate).

Recreation.-- The Morrison Creek watershed is a popular recreation area for local residents. Hiking, mountain biking, and horseback riding are all common. The threats to Morrison Creek lamprey from these activities do not appear to be substantial.