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
The Antarctic Peninsula, which is the northern extension of the Antarctic continent, contains the richest areas of krill
in the Southern Ocean. The extent of se ice cover around this Peninsula has the highest degree of variability relative
to other areas within the distribution of krill. Relatively small changes in climate conditions are likely to exert a
strong influence on the seasonal pack-ice zone in the Peninsula area, which is likely to affect densities of krill in this
region. Because krill are important prey for baleen whales or form critical component of the food chains on which
baleen whales depend, increasing the variability of krill densities or causing those densities to decline dramatically is
likely to have adverse effect on populations of baleen whales in the Southern Ocean.
Reid and Croxall (2001) analyzed a 23-year time series of the reproductive performance of predators that depend on
krill for prey — Antarctic fur seals (Arctocephalus gazella), gentoo penguins (Pygoscelis papua), macaroni penguins
(Eudyptes chrysolophus), and black-browed albatrosses (Thalassarche melanophrys) — at South Georgia Island and
concluded that these populations experienced increases in the 1980s followed by significant declines in the 1990s
accompanied by an increase in the frequency of years with reduced reproductive success. The authors concluded that
macaroni penguins and black-browed albatrosses had declined by as much as 50 percent in the 1990s, although
incidental mortalities in longline fisheries probably contributed to the decline of the albatross. These authors
concluded, however, that these declines result, at least in part, from changes in the structure of the krill population,
particularly reduced recruitment into older age classes, which lowers the number of predators this prey species can
sustain. The authors concluded that the biomass of krill within the largest size class was sufficient to support
predator demand in the 1980s but not in the 1990s.
Similarly, a study of relationships between climate and sea-temperature changes and the arrival of squid off
southwestern England over a 20-year period concluded that veined squid (Loligo forbesi) migrate eastwards in the
English Channel earlier when water in the preceding months is warmer, and that higher temperatures and early
arrival correspond with warm phases of the North Atlantic oscillation (Sims et al. 2001). The timing of squid peak
abundance advanced by 120- 150 days in the warmest years compared with the coldest. Seabottom temperature were
closely linked to the extent of squid movement and temperature increases over the five months prior to and during
the month of peak squid abundance did not differ between early and late years. These authors concluded that the
temporal variation in peak abundance of squid seen off Plymouth represents temperature-dependent movement,
which is in turn mediated by climatic changes associated with the North Atlantic Oscillation.
Climate-mediated changes in the distribution and abundance of keystone prey species like krill and climate-mediated
changes in the distribution of cephalopod populations worldwide is likely to affect marine mammal populations as
they re-distribute throughout the world’s oceans in search of prey. Blue whales, as predators that specialize in eating
krill, seem likely to change their distribution in response to changes in the distribution of krill (for example, see
Payne et al. 1986, 1990 and Weinrich 2001); if they did not change their distribution or could not find the biomass of
krill necessary to sustain their population numbers, their populations seem likely to experience declines similar to
those observed in other krill predators, which would cause dramatic declines in their population sizes or would
increase the year-to-year variation in population size; either of these outcomes would dramatically increase the
extinction probabilities of these whales.
Sperm whales, whose diets can be dominated by cephalopods, would have to re-distribute following changes in the
distribution and abundance of their prey. This statement assumes that projected changes in global climate would only
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