Stock Abundance. Abundance surveys of CI beluga whales prior to 1994 were often incomplete, highly variable, and involved non-systematic observations or counts of concentrations in river mouths and along the upper Inlet. Based on aerial surveys in 1963 and 1964, Xxxxxxxxx (1966) estimated the stock at 300-400 animals, but the methodology for the survey was not described. Sergeant and Xxxxxx (1975) presented an estimate for the Cook Inlet stock as 150-300 animals, but offer no source for this figure. Xxxxxx and Xxx (1979) counted 150 beluga whales in the central Inlet on 3 consecutive days in August 1978, and estimated the total abundance would be at least three times that figure to account for poor visibility. Xxxxxxx (1984) reported on surveys of the upper Inlet between May and August of 1982, and estimated 200-300 belugas were seen in one concentration area. Xxxxxx (1988) stated that an estimate of 450 whales may be conservative because much of Cook Inlet was not surveyed in these efforts. An aerial survey of Cook Inlet in August 1979 resulted in a minimum direct count of 479 beluga whales (Xxxxxxx 1989). Using a correction factor of 2.7 developed for estimating submerged whales under similar conditions in Bristol Bay, he estimated maximum abundance of 1,293 whales. Because this is the most complete survey of the inlet prior to 1994 and incorporated a correction factor for animals missed during the survey in the estimate, the Xxxxxxx summary provides the best available data for estimating the historical abundance of CI beluga whales. NMFS began systematic aerial surveys of beluga whales in Cook Inlet in 1994. Unlike previous efforts, these surveys included the upper, middle, and lower Inlet. Using both observers and videotape, this method also developed correction factors to account for whales not observed due to coloration (calves and juveniles are gray colored and do not contrast with the Inlet water), diving patterns, or because whales were missed by the survey track. These surveys have continued annually and have tracked a decline in abundance of nearly 50 percent between 1994 and 1999.
