The distribution, movements, and relative population abundance of harbor porpoises were studied in the Fish Harbour region of New Brunswick, Canada (lat. 44°59’30”-45°01’00″N, long. 66°54’00”-66°57’00″W), from 1970 to 1978. In any given year numbers of this species were highest in the region between late July and early September. This is also the period during which surface temperatures attain a maximum (10°-12°C) and the largest herring. CIupea harengus catches are usually made. During July-September the porpoise population of the inner (western) part of the study area contained 63% mothers with calves. Changes in relative population abundance were most strongly related with time of year (increasing from early July), tidal amplitude (most present when amplitude is 6.5 m or less), and wind phase (most present during onshore winds). Observation of recognizable individuals revealed consistent specific “territories” and patrolling patterns. A marked decrease in relative abundance in the latter half of the 1970s was noted. This decrease was coincident with a decline in mean midsummer surface temperature over 1974-78 of about 1°C. Unfortunately it was not possible to determine from existing data if major changes in availability of prey species also occurred in the inner Quoddy region during the same period.