Project Title: Population dynamics of right whales off Southern Australia
Chief Investigator: Mr John L Bannister
An annual programme of aerial survey for southern right whales continued off the southern Australian coast in 2007. As in past years flights took place close inshore between C Leeuwin, Western Australia, and Ceduna, South Australia, where the majority of the Australian population seems to approach the coast in winter/spring: cows about to give birth appearing at an average of three years, others less predictably. Two short flights, on 3-4 and 12 August and 28-29 September, 1 October, between C Leeuwin and Twilight Cove, WA, maintained the series of flights on the southern WA coast since 1976. A long flight, between C Leeuwin, WA and Ceduna, SA on 31 August, 1-3 and 6 September, continued the series extended along the coast into South Australia from 1993; as since 2000, an additional leg, on the west coast between Perth and C Leeuwin, was flown on 6 September.Counts and identifying photographs were obtained, with, as usual, emphasis where possible on the latter on the short flights and on the former on the long flight.
Usual concentrations, mainly but not exclusively of cows accompanied by calves of the year the latter in reduced numbers compared with previous years - were encountered in and near Doubtful I Bay (WA), in and east of Israelite Bay (WA), and at Head of Bight (SA). More unaccompanied animals than usual were encountered near Albany, in the Doubtful I Bay area and in and north of Israelite Bay (WA). The number recorded on the long flight in 2007 (286 animals including 57 cow/calf pairs) was considerably fewer than in recent years, although the unaccompanied animals count was not unexpectedly low. Regression analysis, including inspection of residuals, of the long flight data from 1993 (excluding numbers for 1996 and 1997 where there seems to have been some undercounting) gives, for all animals, no evidence of anything other than an exponential increase. But for cow/calf pairs, the 2007 data point is clearly an outlier. For the present the 1993-2006 cow/calf increase rate of 8.10% (95% CI 4.48, 11.83) has been taken as the current best estimate of annual increase rate for that part of the Australian population that visits the southern Australian coast between C Leeuwin WA and Ceduna, SA.
Identifying photographs were again obtained using a digital-camera system. Computerised photographic matching, introduced comprehensively in late 2003, has continued, allied with a computerised database. Of 5069 images available from 1976-2007, mainly from the aerial surveys (including 376 from 2007), 3402 have so far been digitised; comparison has been completed for 3143 images, resulting in 1214 separately identified individuals, mainly from 1980-2004. The sightings database currently contains 2265 separate sighting events mainly for 1976-2002. Current population size for animals visiting the area surveyed is estimated to be ca 2100, with a total Australian population of ca 2400.
