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Gulf of St. Lawrence aster COSEWIC assessment and status report: chapter 9

Population sizes and trends

Thirty-three occurrences of Gulf of St. Lawrence Aster are reported in the Gulf of St. Lawrence, four of which are historical. The population densities are estimated in Tables 1 to 3 based on the fieldwork of Houle (1988b), Godbout (2000 and 2001) and the Piper Project (Sabine Dietz, pers. comm., 2002) for New Brunswick, of Guignion et al.(1995), Houle (1988b), the Island Nature Trust (Stewart and Lacroix, pers. comm., 2001) and Prince Edward Island National Park (Stewart and Lacroix, pers. comm., 2001) for Prince Edward Island, and of Gagnon et al. (1995a and b) and Houle et al. (2002) for the Magdalen Islands. Gulf of St. Lawrence Aster is relatively common in the Magdalen Islands, with 15 extant occurrences, containing a total of more than 12 million individuals. In New Brunswick, five occurrences are still extant, since out of the seven occurrences, two have almost certainly disappeared. In 2002, the counts at these sites were low relative to previous years; with a total of only approximately 1000 individuals. Until the surveys by Guignion et al. (1995), Gulf of St. Lawrence Aster was thought to be particularly rare in Prince Edward Island, since only 13 plants had been located in the national park and 10 at Tignish. Today, we know that there are probably more than 100 000 individuals at the location of the eight extant occurrences, which gives Prince Edward Island the second-largest population of the species after the Magdalen Islands.

The significant difference in the estimates of the total number of individuals for the Magdalen Islands as a whole (1985: approximately 661; 1995: more than 1 million; 2001: more than 12 million) and for Prince Edward Island (1985: 23; 1993: 63 000-80 000; 2002: ~100 000) could be explained by a more intensive survey effort between 1992 and 2001. It is also possible that particularly favourable conditions stimulated the growth of large Gulf of St. Lawrence Aster colonies between 1992-1995 and 1999-2001, particularly in the Magdalen Islands. The summer of 1994, for example, was particularly dry, which may have dried out the upper part of the marshes of the Magdalen Islands more than usual, thereby favouring Gulf of St. Lawrence Aster. According to Houle et al. (2002), the shoreline topography, the exposure to waves and the abundance of deposits of organic matter (mainly eelgrass) have a decisive impact on the local distribution of Gulf of St. Lawrence Aster. It is also possible that unfavourable climatic conditions in certain years result in a significant, although probably temporary, decline in Gulf of St. Lawrence Aster populations.

Populations in the Magdalen Islands

The populations in the Magdalen Islands include a total of 16 occurrences in 11 separate localities. Only one is considered historical (extirpated), i.e. not found for more than 25 years, according to the criteria of Labrecque and Lavoie (2002).


Havre aux Basques sector

The Havre aux Basques lagoon contains the largest population of the species in the Magdalen Islands (Localities 1, 2 and 3, Figure 3). In 1985, Houle and Brouillet had observed two sub-populations totalling approximately 200 individuals in the southwestern part of the lagoon, and near Highway 199 in the eastern zone (Houle and Haber, 1990). During the 1994 and 1995 fieldwork, Gulf of St. Lawrence Aster was reported in five locations around the lagoon (Gagnon et al., 1995a and b). The population, estimated at more than 1 million individuals, covered a total area of more than 5 ha. The largest number of individuals was found in the western sector. Houle et al. (2002) subdivided this population into three occurrences isolated from each other (eastern part of the lagoon, western part of the lagoon and Pointe aux Canots) and including to date a total of 106 to 107 individuals over 3.9 ha.


Île du Cap aux Meules sector

The Étang-du-Nord population (Locality 4) has not been located again since its discovery by Fernald in 1912, despite searches in 1992 (by J. Gagnon and C. Roy), in 1995 (Attention FragÎles) and in 1999, 2000 and 2001 (Houle et al., 2002). It is possible that human activities or gradual closure of the vegetation canopy in this sector have modified the habitat to the point of causing the disappearance of the species.

A population located at Anse aux Étangs (Locality 5) was observed in 1985 by Houle and Brouillet (Houle and Haber, 1990). They had noted approximately 60 individuals there. The site was briefly visited by J. Gagnon in 1995, but no Gulf of St. Lawrence Aster specimens were found there. Subsequently, Houle et al. (2002) found an Aster population there over an area of 5 m2. In 1999 and 2000, there were 100 to 1000 individuals, whereas in 2001, the population had declined to 10 to 100 individuals. It is possible that silting caused by human activity has contributed to the decline in this population.

The Lac aux Canards locality is located near Gros-Cap (Locality 6). A single individual was observed in 1995. Subsequently, despite searches, no Asters were found there between 1999 and 2001.

The Barachois marsh population (Cap de l’Hôpital), in Fatima, included some 20 individuals in 1985 (Houle and Haber, 1990). In 1995, the population was estimated at between 10 000 and 100 000 individuals, covering an area of approximately .5 ha. At the time, the site was disturbed by the passage of all-terrain vehicles and by the operation of a sandpit nearby. In 1999 and 2000, the population remained stable at between 105 and 106 individuals, over areas considered as two separate occurrences (Locality 7 and 8), by reason of their separation by unsuitable habitats over a distance of more than 1 km. In the summer of 2002, however, locality 8 declined drastically from 104 - 105 individuals to 102 – 103 plants presumably due to human activity.


Île de la Grande Entrée sector

A single Gulf of St. Lawrence Aster specimen was observed at Grande-Entrée, Île de la Grande Entrée (Locality 9) by Houle and Brouillet in 1985. The locality was not found during subsequent visits by G. Lavoie in 1992, J. Gagnon in 1995 and Houle and Hamel in 1999, 2000 and 2001.

Fernald (1914) was the first to find Gulf of St. Lawrence Aster at Grande-Entrée in 1912. He did not specify the location where he collected the specimen, but mentioned that the species was found in great abundance, covering the brackish wet sands. This site could be the same as the Bassin aux Huîtres site, which was visited in 1985 by Houle and Brouillet, who discovered approximately 150 individuals there distributed in two sub-populations. In 1995, the number of individuals was estimated at between 105 and 106, distributed over approximately 3 ha. In 1999 and 2000, Houle et al. (2002) counted an equivalent number of individuals there, but over 0.2 to 0.4 ha and separated into three populations by more than 500 m of habitat unsuitable to the species (Localities 10, 11 and 12). It appears that the habitat at this site has been modified by movement of the location of the opening of the basin apparently causing a general decline in the water level and the size of populations 10 and 12 as given in Table 1 (Line Couillard, CDPNQ, pers. comm., 2003).


Île de l’Est sector

The population on the beach at Grande Échouerie (Locality 13) was first visited by Houle and Brouillet in 1985, who discovered approximately 200 individuals there. In 1994, between 200 and 500 individuals were observed at two separate sites. However, in 1995, Gulf of St. Lawrence Aster was no longer present. It appears that this temporary absence may be explained by habitat changes due to a rise in the water level following a summer storm, the accumulation of eelgrass debris on the habitat or gradual closure of the vegetation canopy. In 1999, 2000 and 2001, only 10 to 100 Aster individuals were reported over an area of less of 10 m2.

Between 10 and 100 individuals were observed in 1994 on Île de l’Est, at the northern tip of Étang de l’Est and at Pointe de l’Est (Locality 14). The area occupied was 5 m2 at Étang de l’Est and less than 1 m2 at Pointe de l’Est, where a single individual was reported. In 1999, 2000 and 2001, the population was 100 to 1000 individuals over 100 to 600 m2.

Near the western limit of Clarke Bay (Locality 15), some 30 individuals were counted in 1985 by Houle and Brouillet. In 1994, the population was estimated at approximately 100 individuals covering an area of 25 m2. The temporary opening of the vegetation, caused by the passage of an all-terrain vehicle, seems to have favoured the species, since the habitat, a high marsh dominated by Festuca rubra, is somewhat atypical. Indeed, according to Houle (1988b), Gulf of St. Lawrence Aster is usually found in marshes dominated by Spartina alterniflora, Carex paleacea or Scirpus pungens. In 1999, 2000 and 2001, the population was estimated by Houle et al. (2002) at 103 to 104 individuals, over 100 to 500 m2.

A new Gulf of St. Lawrence Aster occurrence (Locality 16) was discovered in 2001, in the Baie de la Grosse-Île sector (Houle et al., 2002); 103 to 104 individuals occupied an area of more than 1000 m2.

Populations in New Brunswick

Gulf of St. Lawrence Aster populations in New Brunswick include a total of seven occurrences in four separate localities. Of these, only one is considered historical.


Miscou Island

The first Gulf of St. Lawrence Aster specimen collected at this location, by Roberts and Drury (NY and UNB), dates from 1963. Its presence there was verified in 1984, at which time some 100 individuals were counted by Houle and Legault (CAN, DAO, GH, LE, MT; Houle, 1988b). According to Sean Blaney (pers. comm., 2002), this lighthouse site has almost certainly disappeared (Locality 1, Figure 4). However, a new occurrence was discovered in 2002 at Malbaie south, where more than 1000 plants were counted (Dietz, Piper Project, pers. comm., Locality 2). In 2003, the population estimate was 1500 plants (Lewnanny Richardson, pers comm.)


Tracadie

In Tracadie, at the end of the Val-Comeau road, a salt marsh supports a Gulf of St. Lawrence Aster population (Houle, 1988b). The first mention of this population dates back to 1913, when specimens were collected by S.F. Blake (GH, DAO, DS, NY, UC/JEPS). Houle and Legault (MT, Houle, 1988b) confirmed its presence in 1984, where they found a population of some 100 individuals (Locality 3). It had not been seen again for years, but in 1999, Jim Goltz and Maureen Bourque rediscovered it (Maureen Toner, pers. comm.). Approximately 100 plants were counted there in 1999 and more than 1000 in 2000 (Grand Lac, Dietz and Chiasson, 2001). Only 15 plants remained at this locality in 2001 and 12 submerged plants were observed in 2002 (Sabine Dietz, pers. comm.). This site was not visited in 2003.


Kouchibouguac National Park

The St. Louis wharf locality, mentioned by Hinds (1983) for 1979, was explored briefly for Aster (Houle 1988b), but without success (Locality 4). A reconnaissance survey carried out by the park in 1999 also failed to find any Aster population, probably owing to habitat disturbances or changes (mats of eelgrass debris; Dietz and Chiasson, 2001).

In 2000, two new populations were located in Kouchibouguac National Park. One occurrence at the Lac-à-Exilda lagoon contained more than 1000 individuals (Locality 5), while the one in Barachois contained only four plants (Locality 6). However, a severe storm in the fall of 2000 changed the configuration of the dunes where Gulf of St. Lawrence Aster was located and the two occurrences were buried, the first under 60 cm of sand and the second under 30 cm of water (Éric Tremblay, pers. comm.). The situation has remained the same since that time.


Bouctouche Dune

Two populations discovered in 2000 by Valérie Godbout (2000) at Bouctouche Dune included respectively 500 to 1000 and 2 plants (Locality 7). Since 2000, the Gulf of St. Lawrence Aster has been observed at four locations at the Dune (David Mazerolle, 2003). We consider them here as a single occurrence. As was the case for those in Kouchibouguac, the site was affected by combinations of flooding and sand deposition during a storm in 2002 (David Mazerolle, 2003.). It was believed at the time that the plants had been destroyed before seed set. In 2003, roughly 100 plants were counted at this site and remained undisturbed through seed production (David Mazerolle, 2003).

Populations in Prince Edward Island

The Prince Edward Island populations include 10 occurrences, the vast majority of which are located in Prince Edward Island National Park. Two are historical. The year 2002 was a very bad year for Gulf of St. Lawrence Aster populations in Prince Edward Island National Park with several losses of populations due to storm events.


Prince Edward Island National Park

The total Gulf of St. Lawrence Aster population in Prince Edward Island National Park is currently estimated at about 40 000 individuals at the six sites of Covehead Pond, Long Pond, Campbell’s Pond, Western Wetland, Dune Slack and East Marsh. From west to east on the park territory, 13 sites were visited by Guignion et al. in 1992 and 1993. All the localities where the presence of the species is confirmed are located in the eastern half of the park. They have been monitored by the park since 1997.

Covehead Pond (Locality 1, Figure 5) is the closest to the type locality of Brackley Point. It contained 164 individuals in 1992 and 214 in 1993. Between 1994 and 1996, no data were collected. In 1997, 763 individuals were reported, in 1998, 412 individuals, in 1999, between 174 and 243 individuals, in 2001, 123 individuals and in 2002, only 10 individuals (Denyse Lajeunesse, pers. comm.; Stewart and Lacroix, 2001). This site is in decline. The population was completely flooded in 2002 and the individuals counted were under 30 cm of water (Jean Gagnon, pers. comm.).

The Long Pond population (Locality 2), also visited by Houle (1988b), contained only a single individual. Its situation remained the same in 1992 and in 1993. The site was visited from 1997 to 2001 and no individuals were seen there again. Extensive dredging work is being carried out at this site. It is therefore possible that the population has completely disappeared (Lajeunesse, pers. comm.).

Campbell ’s Pond (Locality 3) supported 30 individuals in 1992, but only three in 1993. In 1997, four individuals were seen again there, but none from 1998 to 2001 (Lajeunesse, pers. comm.).

Three populations were recognized at Blooming Point (Western Wetland, Dune Slack and Eastern Marsh), an area not explored during previous surveys. While Western Wetland (Locality 4) had a population of 450 individuals in 1992, it was no longer present in 1993. The site was revisited in 1993, 1998 (Ben Hoteling) and 1999, but no individuals were found. The population has probably disappeared (Lajeunesse, pers. comm.).

The other two populations are the largest in all of Prince Edward Island, with estimates of 15 000-20 000 individuals at Dune Slack and of 48 000-60 000 individuals at East Marsh, both constant between 1992 and 1993. At Dune Slack (Locality 5), the populations were estimated from 1998 to 2001 by Ben Hoteling and his students (Holland College) and in 2002 by Joni Fern Kemp, a student of Christian R. Lacroix (University of Prince Edward Island). In 1998, there were 126 000 individuals over 900 m2, in 1999, 117 600 over 1 200 m2, in 2000, 52 000 over 1 000 m2, in 2001, 65 250 individuals (Stewart and Lacroix, 2001) and in 2002, 2 223 individuals. The population is currently in decline (Lajeunesse, pers. comm.).

Since 1998, the East Marsh occurrence has been divided into two populations (Localities 6 and 7). They were estimated by Ben Hoteling and his students from 1998 to 2000 and by Stewart and Lacroix (2001) and Lacroix (2002, unpublished, Lajeunesse, pers. comm.) in 2001. The East Marsh A population (Locality 6) has gradually decreased from 38 700 individuals in 1998 to only 133 individuals in 2001, over an area of approximately 900 m2. The East Marsh B population (Locality 7) is the only one that has remained of significant size in the entire national park, ranging from 38 400 to 106 000 individuals between 1998 and 2002. In 2002, the population was 44 133 individuals.

The type locality of Brackley Point (Locality 8), where Macoun collected specimens of the plant for the first time in 1888, was revisited in 1912 (Fernald, 1914), 1953 (Erskine and Smith, ACAD) and 1984 (Houle and Legault, 1986). But in 1992, Guignion et al. (1995) observed that the 12 individuals mentioned by Houle (1988b) had disappeared from the site following development work carried out by the park.


Tignish

As early as 1912, Fernald (1914) located a Gulf of St. Lawrence Aster population at Tignish, Prince County, in the north of the island. At that time, it occupied the wet sands behind the strand (GH). Its persistence was verified in 1986 by Houle (1988b), who identified it in the marshes of Tignish Shore (Locality 9). At that time, only 10 individuals were counted in this population. Since then, Sean Blaney and Rosemary Curley have returned to this site twice (pers. comm., Nov. 7 and Dec. 11, 2002), and again in the fall of 2002 with Jean Gagnon, but did not find any plants. According to Jean Gagnon, the habitat has been modified to the point of becoming virtually unsuitable for the species. Nonetheless, Rosemary Curley intends to return again in 2003 to search for the species at Tignish.


Grand Tracadie

The Grand Tracadie locality was mentioned in a source cited by Houle (1988b) dating from 1912 (Locality 10). Searches carried out in 1984 and 1986 failed to find any plants. No other search has been carried out at this site. This locality is considered historical.

Potential sites

Two sites identified as potential habitats for Gulf of St. Lawrence Aster (Houle and Legault, 1986, P.S. map 2), namely John Archies Pond and Clarkes Pond in Prince Edward Island National Park, were visited by Houle (1988b) and by Guignion et al. (1995). Despite the presence of most of the species frequently associated with Gulf of St. Lawrence Aster, these two field studies failed to find any asters. Searches of potential sites were carried out in Prince Edward Island, but outside the national park, by Island Nature Trust (Kate MacQuarrie, pers. comm.) and Jean Gagnon (September and October 2002, pers. comm.), at numerous sites shown in Appendix 1. No new occurrence was found. According to these surveys, the Canavoy site appears to be the best potential habitat, although described by Jean Gagnon as marginal on the basis of the habitats occupied by the species in the Magdalen Islands. Kate MacQuarrie intends to return to visit this site in 2003. According to Jean Gagnon, a storm that occurred before his searches deposited large amounts of eelgrass debris in the habitats conducive to Gulf of St. Lawrence Aster.

In New Brunswick, the Piper Project and the Irving Eco-Centre have conducted searches at a large number of potential sites not yet inventoried in search of Gulf of St. Lawrence Aster (Sabine Dietz, pers. comm., Appendix 2, David Mazerolle, 2003 ). In Kouchibouguac National Park, given the plant’s short fruiting period and the restrictions of the 2000 project (Godbout, 2000), it is quite probable that all potential sites have not yet been identified.

Mistaken occurrences

Hinds (1986) reported Gulf of St. Lawrence Aster in Bathurst (NB) on the basis of a misidentified specimen (Hinds 5803, NB!, in Houle, 1988b). The correct name of that specimen is Symphyotrichum subulatum (Michx.) Nesom var. obtusifolius Fern.

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