During the 2014 winter season, researchers observed lower than usual numbers of humpback whales, including adults and calves, off the coasts of Washington state and Western Australia. Lower numbers were also reported in other areas like Exmouth Gulf and the Kimberley region of Western Australia. While annual fluctuations in whale numbers are normal, the downturn last year appears to have been more significant. Additionally, population estimates for the Western Australia and East Coast humpback groups have been revised downward to 19,000 and 16,000, respectively. This revised population assessment impacts the calculation of orca predation rates on humpback calves.

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Humpback
numbers
down
in
2014
With
the
humpback
migration
gaining
momentum
it’s
timely
to
reflect
back
on
last
season.
During
the
2014
winter,
numbers
of
both
humpback
adults
and
new
calves
observed
along
the
NW
coastal
area
of
WA
were
clearly
down
on
previous
years.
Lower
than
usual
numbers
were
also
reported
in
the
Exmouth
Gulf
waters
from
August
through
Sept
and
into
late
October.
While
its
difficult
to
put
a
number
on
the
low
showing
without
specific
data,
it
has
been
reflected
upon
by
a
several
researchers
and
operators
throughout
the
season.
The
Kimberley
was
similar
with
low
numbers
reported
there
also
-­‐
July
to
Oct.
We
received
similar
reports
about
the
east
coast’s
Group
E
population
when,
over
summer,
we
met
with
operators
and
researchers
from
the
both
northern
area
(Hervey
Bay)
and
Southern
area
(Eden).
The
proportion,
of
animals
that
make
the
full
migration
to
calving/breeding
grounds
does
vary
annually
and
while
it
is
believed
that
some
cows
will
calve
each
year,
most
don’t,
so
a
strong
calving
year
can
be
followed
by
a
calving
downturn
that
picks
up
the
next
and
following
year
as
other
cows
come
on
to
breed
again.
It
may
be
that
this
past
year's
low
is
just
the
low
ebb
in
this
annual
variation.
Additionally,
as
this
population
reaches
its
peak
a
stabilisation
of
annual
growth
would
be
expected.
While
vessel
movements
and
industrial
noise
in
the
area
may
result
in
some
local
displacement,
it
is
clear
that
the
downturn
in
humpback
whale
numbers
last
year
was
part
of
a
bigger
story
or
cycle
It
will
be
interesting
to
see
the
pattern
next
season.
Group
D
population
–
reassessed!
Another
interesting
development
is
the
new
assessment
of
the
population
estimates
for
both
the
breeding
Group
D
(WA
population)
and
Group
E
(east
coast)
humpbacks.
These
indicate
a
previous
over
estimate
in
the
past
and
have
been
revised
down
to
19k
and
16k
respectively.
Regardless
of
the
actual
numbers
both
population
groups
D
and
E
have
been
recovering
at
a
good
rate
for
several
decades
and
appear
in
good
shape.
There
will
come
a
time
though
when
this
increase
slows
and
or
stops
and
a
stable
carrying
capacity
is
reached.
This
revised
population
estimate
for
the
WA
population
(group
D)
significantly
impacts
our
assessment
of
the
natural
mortality
rate
from
predation
by
orca.
With
a
revised
annual
growth
rate
closer
to
7%,
the
current
orca
predation
estimate
would
equal
approx
15%
of
new
calves
each
season
-­‐
based
on
just
18
animals
feeding
over
10
weeks.
The
orca
numbers
would
not
need
to
increase
by
many
to
start
having
a
very
significant
effect…
one
that
could
well
be
part
of
a
balance
not
seen
in
this
area
for
over
half
a
century.