NMFS Biological Opinion on U.S. Navy training ... - Govsupport.us

FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013
and direction of the approaching vessel. While feeding, blue whales react less rapidly and with less obvious
avoidance behavior than whales that are not feeding (Sears et al. 1983). Within the St. Lawrence Estuary, blue
whales are believed to be affected by large amounts of recreational and commercial vessel traffic. Blue whales in the
St. Lawrence appeared more likely to react to these vessels when boats made fast, erratic approaches or sudden
changes in direction or speed (Edds and Macfarlane 1987, Macfarlane 1981). The number of blue whales struck and
killed by ships is unknown because the whales do not always strand or examinations of blue whales that have
stranded did not identify the traumas that could have been caused by ship collisions. In the California/Mexico stock,
annual incidental mortality due to ship strikes averaged 0.2 whales during 1991B1995 (Barlow et al. 1997), but we
cannot determine if this reflects the actual number of blue whales struck and killed by ships.
Status
Blue whales were listed as endangered under the ESA in 1973. Blue whales are listed as endangered on the IUCN Red
List of Threatened Animals (Baillie and Groombridge 1996). They are also protected by the Convention on
International Trade in Endangered Species of wild flora and fauna and the MMPA. Critical habitat has not been
designated for blue whales.
It is difficult to assess the current status of blue whales because (1) there is no general agreement on the size of the
blue whale population prior to whaling and (2) estimates of the current size of the different blue whale populations
vary widely. We may never know the size of the blue whale population prior to whaling, although some authors have
concluded that their population numbers about 200,000 animals before whaling. Similarly, estimates of the global
abundance of blue whales are uncertain. Since the cessation of whaling, the global population of blue whales has
been estimated to range from 11,200 to 13,000 animals (Maser et al. 1981; U. S. Department of Commerce 1983).
These estimates, however, are more than 20 years old.
A lot of uncertainty surrounds estimates of blue whale abundance in the North Pacific Ocean. Barlow (1994)
estimated the North Pacific population of blue whales at between 1,400 to 1,900. Barlow and Calambokidis (1995)
estimated the abundance of blue whales off California at 2,200 individuals. Wade and Gerrodette (1993) and Barlow
et al. (1997) estimated there were a minimum of 3,300 blue whales in the North Pacific Ocean in the 1990s.
The size of the blue whale population in the north Atlantic is also uncertain. The population has been estimated to
number from a few hundred individuals (Allen 1970; Mitchell 1974) to 1,000 to 2,000 individuals (Sigurjónsson
1995). Gambell (1976) estimated there were between 1,100 to 1,500 blue whales in the North Atlantic before
whaling began and Braham (1991) estimated there were between 100 and 555 blue whales in the North Atlantic
during the late 1980s and early 1990s. Sears et al. (1987) identified over 300 individual blue whales in the Gulf of
St. Lawrence, which provides a minimum estimate for their population in the North Atlantic. Sigurjónsson and
Gunnlaugson (1990) concluded that the blue whale population had been increasing since the late 1950s and argued
that the blue whale population had increased at an annual rate of about 5 percent between 1979 and 1988, although
the level of confidence we can place in these estimates is low.
Estimates of the number of blue whales in the Southern Hemisphere range from 5,000 to 6,000 (review by Yochem
and Leatherwood 1985) with an average rate of increase that has been estimated at between 4 and 5 percent per year.
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