Yellow lampmussel (Lampsilis cariosa) COSEWIC assessment and status report: chapter 8

Limiting Factors and Threats

The location within a suburban environment presents several threats to the Sydney River population. A dam constructed in 1902 for industrial and domestic freshwater supply maintains current water levels in the Sydney River. A breach of this dam would lead to a decline in L. cariosa habitat due to both a reduction of shore habitat covered by water and an increase saltwater intrusion upstream of dam. Fish and mussel populations benefit from environmental controls required for maintenance of water quality standards. Nonetheless, the shorelines along the Sydney River are progressively being subjected to residential and service industry development and there is increasing risk of pollution and siltation from property maintenance, transportation accidents, and recreational activities. There are reports of “swimmers itch”, which is caused by the cercariae of various species of trematode parasites, in Blacketts Lake. Cercaria are carried by a variety of freshwater pulmonate snails, but particularly the freshwater snail Stagnicola catascopium catascopium (Say, 1817), a common species throughout eastern Canada (Scott and Burt 1976; Clarke 1981). Depending on the compound used, attempts to control snail populations with molluscicides may be detrimental to mussel populations (Waller et al. 1993).

Lampsilis cariosa populations in the lower Saint John River presently seem to have few threats (Sabine et al. In press). The largest populations, situated in mid-river in the large lower sections of the river, appear to be relatively unexposed, even to muskrat predation, which has been identified as a threat to endangered mussel populations elsewhere (Zahner-Meike and Hanson 2001). While there is some agricultural, residential, and industrial development along the river corridor through most of its length, much of the Saint John River drainage consists of undeveloped forestland. Issues of sedimentation, eutrophication due to agricultural run-off and sewage, and riparian development are problems in some areas within the Saint John watershed, and are increasing in some areas (Harvey et al. 1998). The portion of the Kennebecasis River from which historical records for L. cariosa exist, but in which they have been unable to relocate the species, was recently judged to one of the most heavily encroached riparian zones in New Brunswick (Brillant pers. comm. 2002).

Sabine et al. (In press) suggest that further study on effects of low, late summer, water levels in the lower Saint John River on L. cariosa mortality, in terms of elevated water temperatures, exposure, and saline penetration, are required. The current downstream limit of L. cariosa on the Saint John River coincides closely with the current upstream limit for saltwater intrusion. However, during periods of low water the saline front penetrates farther inland. Sabine et al. (In press) observed some mortality on the Saint John River in late August and early September 2001, a particularly dry year. They suggested that some of this mortality may have been due to low water levels and elevated water temperatures over sand bars.

The introduced zebra mussel (Dreissena polymorpha) poses a severe threat to native freshwater mussel populations elsewhere in North America (Ricciardi et al. 1998; Martel et al. 2001). Although White (2001) suggested that there was a low risk of establishment of D. polymorpha in the Sydney River, Sabine et al. (In press) identified the zebra mussel as a potential threat to L. cariosa in New Brunswick. While D. polymorpha has not been recorded in New Brunswick to date, its ability to colonize freshwaters with non-unidirectional flow, such as lakes or tidal rivers, indicates that it could potentially spread throughout the lower Saint John River if accidentally introduced. 

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