Assessment of injuries and recovery monitoring of Prince William Sound killer whales using photo-identification techniques Exxon Valdez Oil Spill Restoration Project final report

"Photo-identification studies of individual killer whales inhabiting Prince William Sound were collected from 1989-91 and from July to September 1993 to determine the impact of the spill on whale abundance and distribution (1989-1991) and monitor recovery (1993). Concurrent photo-identification studies were also conducted in Southeast Alaska to determine if PWS killer whales were displaced to other areas between 1989 and 1991. Despite increased effort, the number of encounters with PWS killer whales appears to be decreasing. Analysis of photographic data revealed 14 animals missing from AB pod over the three-year period. Mortality rates for AB pod ranged from 3.1% in 1988 to 19.4% in 1989, 20.7% in 1990, and 4.3% in 1991. Zero mortality occurred in 1992 and 1993. Mortality rates on the order of 20% are unprecedented for North Pacific killer whales. No new calves were born into AB pod in 1989 or 1990. There was one calf born in 1991, two born in 1992, and one born in 1993. AB pod size in 1988 was 36; in late 1993 the pod had 26 members. The cause(s) of the disappearance of 14 killer whales from AB pod is unknown. We assume, that the whales are dead from natural causes, a result of interactions with fisheries, from the spill, or a combination of these causes"--Abstract. 1994 Funding: Exxon Valdez Oil Spill Trustee Council.; NMFS (National Marine Fisheries Service) Library Public Domain 1862