Offshore
research
 In
the research, conducted in the offshore area between June 29 and September
23, a total of 100 minke whales, 50 Bryde's whales, 39 sei whales
and 5 sperm whales were sampled. As a result of the research, segregation
in habitat was observed among minke, Bryde's and sei whales. Also
segregation in feeding patterns was confirmed. When the habitats of
minke and sei overlap in the same area, the possibility was suggested
that the two species segregate their distribution and food in terms
of time and space.
Analysis of the stomach contents of the samples made clear that important
fishery species such as anchovy, Pacific saury and squid were consumed
by minke, Bryde's and sei--all of them baleen whale species. For sperm
whales (toothed whale), it was confirmed that they feed on surface
flying squid besides deep-sea squid, suggesting that sperm whales
are closely related to the surface ecosystem. These findings,along
with the survey on feed species carried out concurrently with sampling
research in the same region, provided valuable scientific information
necessary to clarify the presence of competition over food between
cetaceans and fisheries.
|
Anchovy found in the stomach
of a Bryde's whale from last year's research |
|
Sighting surveys,
also conducted in parallel with the research catch program by a dedicated
sighting vessel and research catchers, clarified the presence of a
substantial number of sei, Bryde's, sperm and fin whales in the region,
besides minke whales whose abundance had been confirmed earlier. In
addition to these four targeted species, a substantial number of blue,
fin and humpback whales were spotted, indicating that whale stocks
in the western North Pacific was abundant.
Coastal research
In
the coastal research conducted from September 10 to October 12 in
the area of 30 nautical miles off Kushiro, Hokkaido, northernmost
Japan, a total of 50 minke whales were sampled, and mainly minke and
sperm whales were sighted.
Regarding
the feeding habit, it was confirmed that minke whales mainly feed
on anchovy on the continental shelf, pollock and squid on the slope
of the continent and Pacific saury and krill in the offshore area.
These
results by and large coincide with the results of the survey on feed
species, suggesting that minke whales make feeding migration to the
offshore area of Kushiro where food is abundant.
This reflects the fact that minke whales as a flexible feeding strategy
in accordance with the occurrence of feed species. Thus, it was confirmed
that minke whales prey on large quantities of fishery resources such
as saury and sardines in good fishing grounds. Sizeable information
needed for clarification of the impact predation by cetaceans give
to fisheries was obtained.
As
a result of sighting surveys off Kushiro, large numbers of large whales
were found, among them minkes were prominent. Also the fact that minke
whales were spotted in large number close to the coast shows that
this species is distributed continuously from offshore to the area
close to the coast. |
