CETACEANS IN THE GREAT SOUTH CHANNEL, 1979-1989 - RIGHT-WHALE (EUBALAENA-GLACIALIS)

A continuous 11-year time-series of aerial and shipboard survey data i n the Great South Channel region reveals a remarkably consistent patte rn of right whale distribution, with several interesting variations. R ight whales occur in the area during the spring, with a distinct peak in May. Arrival and departure dates appear to vary by a month or more between years. The distribution is concentrated in the deeper basin no rth of the V-shaped 100-m isobath and a thermal front which approximat ely parallels the isobath. Within a single year, this concentration te nds to be within a relatively small area and may remain stable for day s or weeks. The center of distribution changes between years, and in 1 984, 1987 and 1989 was on the eastern side of the basin rather than th e ''typical'' western side. At any one time, nearly all of the right w hales may aggregate into one to several clusters of <10 km(2) each. A gradual southward shift in the center of distribution can be observed as the season progresses. Single-day abundance estimates, uncorrected for animals missed while submerged, ranged up to 179 animals. There wa s a statistically significant long-term increase in right whale sighti ng rates in the region, after correcting for estimated increases in su rvey, efficiency, of 3.8% per year. This suggests that the population might be recovering, albeit slowly, from extreme depletion. It is like ly that a significant proportion of the western North Atlantic right w hale population utilizes in the Great South Channel region as a feedin g area each spring, aggregating to exploit exceptionally dense copepod patches.