EPA's Vessel General Permit and Small Vessel General

estimated the populations at 300-400 whales, but the methodology was not described nor did he
report the variance around these estimates. Other estimates were incomplete due to the small
area the survey focused upon (e.g. river mouth estimates; e.g., Hazard 1988). The most
comprehensive survey effort prior to the 1990s occurred in 1979 and included transects from
Anchorage to Homer, and covered the upper, middle and lower portions of Cook Inlet. From this
effort, and using a correction factor of 2.7 to account for submerged whales Calkins (1989)
estimated the 1979 abundance at about 1,293 whales.
In 1993, NMFS began systematic aerial surveys of beluga whales in Cook Inlet and like the 1979
survey cover the upper, middle and lower portions of Cook Inlet. The survey protocol involves
using paired observers who make independent counts at the same time a video of the whale
grouping is recorded. Each group size estimate is corrected for subsurface and missed animals, or
if video counts are not available then additional corrections are made (Allen and Angliss 2010).
Between 1979 and 1994, according to above noted population estimates, Cook Inlet beluga
whales declined by 50%, with another 50% decline observed between 1994 and 1998. Using a
growth fitted model Hobbs et al., (2008) observed an average annual rate of decline of -2.91%
(SE = 0.010) from 1994 to 2008, and a -15.1% (SE = 0.047) between 1994 and 1998. A
comparison with the 1999-2008 data suggests the rate of decline at -1.45% (SE=0.014) per year
(Hobbs et al., 2008). Given that harvest was curtailed significantly between 1999 and 2008,
NMFS had expected the population would begin to recover at a rate of 2-6% per year. However,
abundance estimates demonstrate that this is not the case (Hobbs and Shelden 2008).
In conducting its status review, NMFS ran a number of population viability analyses (PVAs) to
estimate the time to extinction for Cook Inlet beluga whales. The models were sensitive to a
variety of parameters such as killer whale predation, allee effects and unusual mortality events.
The best approximation of the current population incorporated killer whale predation at only one
beluga whale per year and allowed for an unusual mortality event occurring on average every 20
years. According to this model, there is an 80% probability that the population is declining, a
26% probability that the population will be extinct in 100 years (by 2108) and a 70% probability
that the population will be extinct within 300 years (by 2308).
Threats
Natural Threats. Natural threats to Cook Inlet beluga whales include stranding, predation,
parasitism and disease, environmental change and genetic risks associated with small populations
(e.g., inbreeding, loss of genetic variability). As noted in NMFS’ Cook Inlet beluga whale
conservation plan (NMFS 2008b),beluga whales may strand accidentally as they occupy shallow
water areas or escape predators, or as a result of diseases, illness or injury. Given the extreme
tidal fluctuations in Cook Inlet, beluga whale strandings are not uncommon. According to NMFS
(2008b) killer whales have been observed in Cook Inlet concurrent to beluga whale strandings
and evidence of killer whale attacks is apparent in some beluga whale strandings.
Over 700 beluga whales have stranded in Cook Inlet since 1988, many of which occurred in
Turnagain Arm and often coincided with extreme tidal fluctuations (NMFS 2008b). Where
stranding occurs from extreme tidal fluctuations and animals are out of the water for extended
periods the risk of mortality increases from cardiovascular collapse. Ten hours may be the upper
limit for out of the water for beluga whales before serious injury or death occurs (NMFS 2008b).
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