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  Results of the 2005 Survey of the Reintroduced Sea Otter Population in Washington State PDF Format - [878K]
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Results of the 2005 Survey
of the Reintroduced The survey was conducted from 12-14 July, and included the inshore area from Pt. Grenville to Tongue Pt. Biologists and volunteers from the Washington Department of Fish and Wildlife (WDFW), United States Fish and Wildlife Service, Olympic Coast National Marine Sanctuary, The Seattle Aquarium and Point Defiance Zoo and Aquarium participated in the survey. Counting conditions this year ranged from good to excellent. Methods
All of the sea otter range in Washington was surveyed from a fixed-winged aircraft (Cessna 185) and included coverage of coastal waters from Point Grenville on the outer coast to Tongue Point in the Strait of Juan de Fuca. Additional counts were made by observers on the ground at Cape Johnson, Yellow Banks, Sand Point, Cape Alava, Duk Point (Seafield Creek), and inshore of Father and Son. Typically, two surveys are conducted each day over a period of 3 or 4 days, weather permitting. Thus, when conditions are favorable, six surveys of the entire range are completed. An offshore leg added in 1999 to detect open water groups was included again this year. This year, we were able to complete six surveys of the sea otter’s range in Washington. The survey total was calculated by summing the highest daily total for the southern (Pt Grenville to La Push) and northern (La Push to Pillar Point) segments of the sea otter range. The high counts this year were on 14 July for both segments of the range. This method assumes little or no movement between the two segments during the survey period. Examination of survey data from years past, as well as documented movements of instrumented sea otters by USGS researchers in Washington support this assumption. Large groups (>20) observed from the air were generally counted and photographed with a digital camera. Digital images were later counted (3 times) and the resulting numbers were used when image quality was good and ground counts were not available or were less than the digital image count. Results
The highest count
for the survey was 814 sea otters, an increase of about 10% over 2004
(Table 1). The finite rate of increase for this population since 1989
has remained 8.2%. This year 53 pups were counted during the high counts,
with most pup observations made from ground observation sites. It is not
unusual for pups to go undetected or be undercounted from the aircraft
because they are difficult to distinguish from adults; however, experienced
ground counters can easily make the distinction. This year pups were seen
at all ground stations. Pups were also observed at Destruction Island,
Diamond Rock, inshore from Perkins Reef (Rock 443), Giants Graveyard,
and Anderson Point from the air. More pups are now being recorded in aerial
counts because of the use of digital photography, which allows close examination
of animals in groups when the digital image is counted. In some cases
they may not appear in the summary because they were not observed during
the highest counts. The pup to independent ratio increased from 13:100
in 2004 to 24:100 this year.
Survey results this
year indicate growth of the Washington sea otter population continues
to remain positive (Figure 1). Survey data indicate Washington’s sea otter
population may be approaching equilibrium density north of La Push where
the rate of increase has been about 3.5% since 1989. Nevertheless, there
still appears to be some quality unoccupied habitat available north of
Point of Arches, and again this year significant numbers of otters, including
pups, were sighted between Anderson Pt. and Bahobohosh Pt in Makah Bay
(Table 1). South of La Push the population has been growing at about 20%
per year since 1989. This trend began in the mid- 1990s and has continued
to date. These results illustrate the importance of continuing annual
surveys to monitor population trends and changes in distribution.
The distribution (Figure
2) of sea otters has continued to change in recent years with the larger
proportion of the population occurring south of La Push (Figure 3). In
2002, the southern segment accounted for about the same percentage of
the total population as the northern, 49 and 51 percent respectively;
however in 2003 the percentage shifted in favor of the south end with
46% north and 54% south, in 2004 it was 45% and 55%, and this year it
was relatively unchanged at 46% and 54%, respectively.
As in the previous
two years, the Diamond Rock raft located about 4 kilometers south of the
Perkins Reef (Rock 443) group and 1.5 kilometers north of the Hoh River
mouth was still present. Pups have been seen in this group for the past
four years and along with the female group at Destruction Island (DI)
represent the most southern groups of breeding females in Washington.
The single largest concentration of sea otters continues to be located
at DI with 307 otters counted during this year’s survey. Consistent with
recent surveys, a large male group continues to use the northeast reef
and kelp bed areas for resting and a reproducing female raft is still
located at the west end of the island. Counts made at the south end of
the range over the survey suggest that females move regularly between
three locations, Destruction Island, Diamond Rock, and Perkins Reef (Rock
443) areas. No otter groups were located during offshore survey legs.
As in 2004, our survey
area did not include inland waters east of Port Angeles, although we are
aware of credible sightings of scattered individual sea otters in the
San Juan Islands and Puget Sound in recent years. Most of these sightings
have been of single animals. No groups have been noted to date and we
believe the number of sea otters frequenting the inland waters would not
add significantly to the population total. Also of note, the groups that
moved into the western Strait of Juan de Fuca during the past winters
have not appeared since 2000. A single sea otter was observed at Tatoosh
Island this year, which has often been the case in years past, and 14
otters observed near Kalaloch were the most southerly sightings.
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