Victorin's water-hemlock (Cicuta maculata) COSEWIC assessment and status report: chapter 5
Habitat requirements
Victorin’s water-hemlock prefers thick surface deposits (over 15 cm) of fine or mixed texture (never coarse), with highly variable stoniness, from no stones to very stony. Plant densities are much lower in sectors covered by gravel and pebbles (Robert, 1993). In some localities, the water pH ranges from 8.5 (Anse Saint-Vallier) to 8.0 (Anse de Berthier and L’Islet) (Rousseau, 1930, 1932). Surface deposits consist of fragmented schist and watery silt (Legault, 1986), with a pH of 7.5 (Rousseau, 1930).
Victorin’s water-hemlock occurs in tall, dense prairie cordgrass beds in the mid- and upper intertidal zones (Robert, 1993; Brouillet et al., 1996). In the mid-littoral zone or on thin substrate, it sometimes grows in open, short grass beds. This zone is covered by water for two to three hours a day during equinoctial high tides, but is seldom reached by low high tides. Brouillet et al. (1996) observed Victorin’s water hemlock in 43 segments (8.88 per cent) of their 34 sampling sites. Of that number, 32 segments (74.42 per cent) were in the upper littoral, the preferred habitat of Victorin’s water-hemlock. In 11 segments (25.58 per cent), several isolated individuals were counted in the upper part of the mid-littoral zone, which is submerged at mean high water. However, these individuals were smaller than those in the upper littoral (Robert, 1993).
Two species designated as species of special concern by COSEWIC share the same habitat as Victorin’s water hemlock. One population of Provancher’s fleabane and most populations of Victorin’s gentian grow in proximity to Victorin’s water hemlock.
Trends
Legault (1986) reports that Victorin’s water-hemlock was known from 10 localities (9 localities without the revised population of Batiscan). Since his report, several new populations have been discovered and, in the summer of 2002, the Quebec Natural Heritage Information Centre (CDPNQ) sent information on 42 occurrences of the plant. Several of the localities present in the database are erroneous, despite the fact that Coursol (1999) reported that a number of specimens of Brouillet et al. (1996) were referred to var. maculata. After verification, the CDPNQ also created two occurrences at Saint-Jean-Port-Joli for a single locality, although these two sub-populations are less than 100 metres apart. The revision of two herbarium specimens (Batiscan and Cap Saint-Ignace for var. maculata and Chandler for var. victorinii) also results in changes. The CDPNQ has been advised of these problems and the data will soon be corrected to give a total of 39 occurrences.
There has been a significant loss of potential Victorin’s water-hemlock habitat in a number of places such as in the Quebec City metropolitan area. Road and railroad construction on the tidal flats of the St. Lawrence River has almost completely destroyed the mid- and upper littoral zones of potential habitats between Boischâtel and Cap-Rouge. Habitat quality has been seriously affected by the filling of the upper littoral and the construction of retaining walls for many homes in Lévis, Saint-Romuald and several other residential sectors bordering the St. Lawrence River near areas where populations have been documented.
The introduction of tighter environmental legislation seems to have halted or slowed this trend. The major sampling effort by Brouillet et al. (1996) has advanced the state of knowledge of estuarine taxa and their distribution. Since the status report by Legault (1986), 30 new populations have been discovered, and certain localities, such as Île aux Grues, Pointe Martinière at Lévis, L’Islet and Pointe Dauphine at Saint-Jean, now have large populations, accounting for between 20 and 40 per cent of the total number of Victorin’s water hemlock plants. Since the report by Brouillet et al. (1996), the general trend appears to be stable, but there are still a number of threats that could alter this trend.
Protection/ownership
Two localities (Anse Saint-Vallier and Grosse Île) are located within the boundaries of protected areas: the Saint-Vallier Migratory Bird Sanctuary and the Grosse Île and the Irish Memorial National Historic Site. Other ill-defined historic populations may occur within the boundaries of other protected areas, i.e., the L'Islet and Trois-Saumons migratory bird sanctuaries. In addition, the organization Nature Conservation de la nature Québec owns part of the site on which the Saint-Vallier population occurs.
Most Quebec localities of Victorin’s water-hemlock do not have conservation status and ownership is therefore unclear. Victorin’s water hemlock habitat is found on public lands under the jurisdiction of the Quebec government. However, occurrences in the RCM of Cote-de-Beaupré (Boischâtel and Ange-Gardien) may be on private land and may extend to the low water mark, at low tide. Official boundary surveys (Cadastral surveys) are needed to identify these sites.
The Regulation Respecting Motor Vehicle Traffic in Certain Fragile Environments (R.S.Q., c. Q-2, r. 2.2) protects Victorin’s water-hemlock habitat by prohibiting access to the tidal flats of the St. Lawrence River by motor vehicles. The application and enforcement of this regulation could put an end to the problem of ATV traffic at Saint-Augustin-de-Desmaures.
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