Abstract

Serious concerns have been raised regarding the status of the harbour porpoise populations in the North Atlantic and specifically for those inhabiting Atlantic Canadian waters. In 1991 harbour porpoise in these waters were classified as “Threatened” by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Since this time, important new data have become available in some parts of their range while in others, significant data gaps continue to exist. In order to gain a clear understanding of the current state of our knowledge of harbour porpoise in Atlantic Canada, the Department of Fisheries and Oceans convened a workshop to discuss harbour porpoise in Dartmouth, Nova Scotia 26-28 March 2001. Sixteen scientists from Canada, the United States and Greenland participated. The objectives of the workshop were to 1) compile available information on the biology, abundance and by-catch of harbour porpoise in eastern Canadian waters, 2) identify gaps in our existing knowledge required to assess the status of harbour porpoise in these waters, 3) review methods for estimating harbour porpoise abundance and distribution, and 4) review methods for estimating harbour porpoise incidental mortality in fishing gear. Information on stock identity, biological parameters, abundance, distribution, ecology, by-catch, and by-catch mitigation methods were presented and discussed. It was concluded that available data on stock identity are consistent with the three putative populations (Bay of Fundy/Gulf of Maine, Gulf of St. Lawrence and Newfoundland) proposed in the 1980s, but that significant sampling gaps remain. It was agreed that data exist to construct simple population models although these models will be limited due to the absence of data on survivorship of harbour porpoise. Good estimates of abundance in the Bay of Fundy/Gulf of Maine area are available, whereas estimates of abundance in the Gulf of St. Lawrence are incomplete and non-existent in Newfoundland and Labrador waters. Obtaining estimates in these latter areas was considered to be the highest priority for research. Although diets have been examined in various areas, ecological factors affecting porpoise abundance in Atlantic Canada are unknown. Estimates of current by-catch are not available from the Gulf of St. Lawrence and Newfoundland areas; the implementation of such monitoring programs is a high priority. Monitoring programs should include a variety of methods to determine levels of by-catch and must cover all of the fisheries that may catch porpoise. A number of mitigation methods have been shown to be effective in reducing by-catch. These include the use of pingers, time-area enclosures and gear modifications. Porpoise by-catch has likely declined in a number of areas, however, due to reduced effort in gillnet fisheries.