Prepared by D.J. White

Ogden’s Pondweed (Potamogeton ogdenii) occurs in eastern Ontario, western Connecticut, eastern and central New York, central Vermont, and western Massachusetts. Ogden’s Pondweed is considered critically imperiled globally and is designated as endangered in Massachusetts and New York. It is listed as endangered on the Species at Risk in Ontario (SARO) List under the province’s Endangered Species Act, 2007 and on Schedule 1 of the federal Species at Risk Act.

In Ontario, this species is known only from Hastings County (1873), Murphys Point Provincial Park (1974), and Davis Lock on the Rideau Canal (1987). The Hastings County record is not possible to locate because the specimen lacks locality data. Neither the Murphys Point nor the Davis Lock sites were re-confirmed during field work by the author in 2005 or 2006 but suitable habitat exists in the vicinity of both of these sites. The species is likely still present in Ontario.

Ogden’s Pondweed is a submerged, annual aquatic plant that reproduces mainly by winter buds or turions. Fruits are also produced. The species grows in clear, shallow water of slow-moving streams, beaver ponds, and lakes. This water is generally highly-alkaline.

Potential threats to Ogden’s Pondweed are habitat loss, eutrophication and competition from native and invasive plants. The low number of populations globally may be a limiting factor for the species.

The long-term recovery goal for Ogden’s Pondweed is to ensure the persistence of the species in Ontario. Since Ogden’s Pondweed has not been recorded in Ontario since 1987 (at Davis Lock), the short-term recovery goal must be to determine if and where the species still occurs in the province.

Recovery objectives are to:

  1. Determine if and where Ogden’s Pondweed occurs in Ontario.
  2. If extant populations can be found, determine the population size, habitat parameters, population dynamics, and specific threats for those occurrences.
  3. Ensure the protection of Ogden’s Pondweed habitat where the species still occurs.
  4. Consider the feasibility and appropriateness of re-introducing the species to suitable or former sites (if no longer extant) if sufficient habitat is present, threats to the species can be mitigated, and proven methods for re-introduction can be found.

In order to meet these objectives, a number of approaches to recovery have been suggested including protecting known populations and associated habitat by developing site-specific management strategies, monitoring extant sites and monitoring the effectiveness of any management actions undertaken.

Searches over several years may be required to confirm the presence or absence of the species at the Davis Lock and Murphys Point sites. As a precautionary measure, it is recommended that the following areas be prescribed as habitat within a habitat regulation. The portion of Black Creek within Murphys Point Provincial Park, Hoggs Bay and the appropriate habitat within the associated bays and shallow water areas of adjacent Big Rideau Lake within the park. The regulation should also include the aquatic habitat downstream of Davis Lock. The specific boundaries of these areas should be determined on a site-specific level based on further study.