NOAA Technical Memorandum NMFS-AFSC-99

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Alaska Fisheries Science Center

March 1999

by

J. L. Sease, J. M. Strick, R. M. Merrick, and J. P. Lewis

Aerial and Land-Based Surveys of

Steller Sea Lions (Eumetopias jubatus)

in Alaska, June and July 1996
NOAA Technical Memorandum NMFS

The National Marine Fisheries Service's Alaska Fisheries Science Center

uses the NOAA Technical Memorandum series to issue informal scientific and

technical publications when complete formal review and editorial processing

are not appropriate or feasible. Documents within this series reflect sound

professional work and may be referenced in the formal scientific and technical

literature.

The NMFS-AFSC Technical Memorandum series of the Alaska Fisheries

Science Center continues the NMFS-F/NWC series established in 1970 by

the Northwest Fisheries Center. The new NMFS-NWFSC series will be used

by the Northwest Fisheries Science Center.

This document should be cited as follows:

Sease, J. L., J. M. Strick, R. L. Merrick, and J. P. Lewis. 1999. Aerial 

and land-based surveys of Steller sea lions (Eumetopias jubatus) in 

Alaska, June and July 1996. U.S. Dep. Commer., NOAA Tech. Memo. 

NMFS-AFSC-99, 43 p.

Reference in this document to trade names does not imply endorsement by

the National Marine Fisheries Service, NOAA.
March 1999

NOAA Technical Memorandum NMFS-AFSC-99

by

J. L. Sease, J. M. Strick, R. M. Merrick, and J. P. Lewis

Aerial and Land-Based Surveys of

Steller Sea Lions (Eumetopias jubatus)

in Alaska, June and July 1996

Alaska Fisheries Science Center

7600 Sand Point Way N.E., BIN C-15700

Seattle, WA 98115-0070

Alaska Department of Fish and Game

333 Raspberry Road

Anchorage, AK 99518

U.S. DEPARTMENT OF COMMERCE

William M. Daley, Secretary

National Oceanic and Atmospheric Administration

D. James Baker, Under Secretary and Administrator

National Marine Fisheries Service

Rolland A. Schmitten, Assistant Administrator for Fisheries

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iii

ABSTRACT

The National Marine Fisheries Service and the Alaska Department of Fish and Game

conducted aerial and land-based surveys of Steller sea lions (Eumetopias jubatus) during June and

July 1996 from Southeast Alaska to the western Aleutian Islands. We counted a total of 41,529

adult and juvenile (non-pup) sea lions at 280 rookery and haul-out sites. Of these sea lions,

30,454 (73.3%) were at 95 trend sites (rookeries and haulouts) and 22,562 (54.3%) were at 33

trend rookeries. The 1996 count at the 95 trend sites was a decline of 18.0% since 1991, 12.6%

since 1992, and 7.6% since 1994. Overall declines were slightly less for all surveyed sites. The

average annual rate of decline from 1991 to 1996 was about 3.7% for trend sites and trend

rookeries and 2.1% for all surveyed sites.

The western stock of Steller sea lions in Alaska includes animals from the eastern Gulf of

Alaska through the western Aleutian Islands. In 1996 we counted 30,622 non-pups at 222

surveyed sites. Of these, 22,223 (72.6%) were on 82 trend sites and 16,358 (53.4%) were on 30

trend rookeries. For the 82 trend sites, the 1996 count represented declines of 27.2% from 1990,

24.5% from 1991, 18.6% from 1992, and 7.9% from 1994. The annual rates of decline were

about 5.5% for trend sites and trend rookeries (1990 to 1996) and 3.8% for all surveyed sites

(1991 to 1996). In the Kenai Peninsula to Kiska Island index area, a sub-area within the Alaska

portion of the western stock, we counted 24,625 non-pup sea lions at 189 surveyed sites. Of

these, 17,900 (72.7%) were at 69 trend sites, and 13,905 (56.5%) were at 26 trend rookeries.

The 1996 count for the 69 trend sites was a decline of 21.3% from 1990, 17.7% from 1991,

13.4% from 1992, and 4.3% from 1994. The estimated annual rates of decline were 4-5% for

trend sites and trend rookeries (1990 to 1996) and 2% for all surveyed sites (1991 to 1996).
iv

The eastern stock is represented in Alaska only by Southeast Alaska. In 1996 we counted

10,907 non-pups at 58 surveyed sites: 8,231 (75.5%) at 13 trend sites and 6,204 (56.9%) at 3

trend rookeries. Non-pup numbers at the 13 trend sites increased by 6.7% to 8.9% compared to

the 1990, 1991, and 1992 surveys but declined 6.7% since 1994. Overall, non-pup numbers in

Southeast Alaska increased by an average of about 2% per year from 1990 to 1996.

Pup count trends were not consistent at all rookeries. The number of pups at the three

rookeries in Southeast Alaska in 1996 (3,714) was an increase of 3.2% from 1990 but a decline of

1.5% from 1994. Pup counts at the two rookeries in the eastern Gulf of Alaska experienced

greater declines from 1994 to 1996 of 24% at Seal Rocks (352 pups) and 41% at Fish Island

(232). The 632 pups at Marmot Island was a decline of 61% from 1991 and 21% from 1994.

The pup count at Outer Island (114) changed little from 1994, after a decline of 67% from 1990

to 1994. Pup counts at Atkins Island (366) in the western Gulf of Alaska and at Ugamak Island

(706) in the eastern Aleutian Islands declined 15% to 17% from 1990 but increased 13% to 23%

compared to 1994.
V

CONTENTS

Introduction 

Methods 

Abstract 

Aerial Surveys of Non-Pups 

Land-Based Pup Surveys 

Data Analysis 

Results 

Aerial Surveys of Non-Pups 

Alaska State-Wide 

Comparison of Western and Eastern Stocks

Kenai to Kiska Index Area 

Subareas Outside of the Kenai to Kiska Index Area

Proportion of Non-pups on Rookeries

Land-Based Pup Surveys 

Discussion 

Acknowledgments 

Literature Cited 

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14
INTRODUCTION

The National Marine Fisheries Service (NMFS) and the Alaska Department of Fish and

Game (ADF&G) conducted aerial and land-based surveys of non-pup (adult and juvenile) and pup

Steller sea lions (Eumetopias jubatus) from Southeast Alaska through the western Aleutian

Islands during June and July 1996. The 1996 surveys continued a series of surveys conducted in

Alaska since the mid-1970s (Braham et al. 1980, Calkins and Pitcher 1982, Loughlin et al. 1984,

Met-rick et al. 1987, Loughlin et al. 1990, Merrick et al. 1991, Merrick et al. 1992, Sease et al.

1993, Strick et al. 1997). This report, like others in the recent years (Met-rick et al. 1991, Merrick

et al. 1992, Sease et al. 1993, Strick et al. 1997), focuses primarily on counts of non-pup Steller

sea lions at trend rookery and trend haul-out sites. Trend analyses concentrate on counts from

1990 or 1991 to 1996. Longer historical perspectives are included in Met-rick et al. (1991: for

1956-90) and Sease et al. (1993: for 1976-92).

In November 1990, the NMFS listed Steller sea lions as “threatened” range-wide under

the U.S. Endangered Species Act (55 Federal Register 49204). Ongoing studies of rnitochondrial

DNA (Bickham et al. 1996) identified stock differences within the population that coincided with

differing population trends, separated approximately at 144° W. long. (Loughlin 1997). An

eastern stock occurs from Southeast Alaska to California whereas a western stock occurs from

Prince William Sound, Alaska, westward to Russia and Japan. This two-stock model was

incorporated into management actions in June 1997 with the listing of the western stock as

“endangered” under the ESA. The eastern stock remains classified as threatened (62 Federal

Register 24345).
2

METHODS

The 1996 survey adhered to protocols of earlier aerial and land-based surveys (Braham et

al. 1980, Calkins and Pitcher 1982, Merrick et al. 1991, Merrick et al. 1992, Loughlin et al. 1992,

Sease et al. 1993, Strick et al. 1997). Most of the analyses in this report focus on “trend sites.”

Trend sites are those rookeries and major haul-out sites surveyed consistently from the 1970s to

the present, thus allowing identification of population trends on a decadal scale. Trend sites

include the majority of animals observed in each survey (73.3% in 1996). Most of the other areas

are small haul-out sites. The only major rookeries that are not trend sites are located on Outer

and Attu Islands. Rookeries are those sites where adult males actively defend territories, pups are

born and mating takes place. Haul-out sites are those where sea lions predictably rest on land

(haul out), but where few or no pups are born (Calkins and Pitcher 1982, Loughlin et al. 1984).

The list of trend sites was reduced from 103 to 95 in 1992 by combining some adjacent

sites (e.g., Ugamak and Round Islands in the eastern Aleutian Islands) into single new trend sites

(Sease et al. 1993). The number of trend sites increased to 96, and the number of trend rookeries

increased to 33, beginning with this report to accommodate the separate listing for the rookeries

at Cape Sabak and Gillon Point, Agattu Island, in the western Aleutian Islands. These are merely

“book-keeping” changes that do not affect the total counts of sea lions on trend sites. Only one

trend site, Sitkagi Bluffs in the eastern Gulf of Alaska, was not surveyed in 1996.

Aerial Surveys of Non-Pups

The NMFS and ADF&G counted and photographed adult and juvenile Steller sea lions

from aircraft flying over rookery and haul-out sites from Forrester Island in Southeast Alaska to
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Attu Island in the western Aleutian Islands (Fig. 1) from 10 June to 22 June 1996 (Table 1).

Flight tracks included traditional sea lion rookeries and haul-out sites (Calkins and Pitcher 1982,

Loughlin et al. 1984), but potential haul-out sites along the flight path also were examined

en route. Under ideal conditions, we surveyed each site at 150-200 m (500-650 ft) altitude, l00-

150 knots air speed, and 500 m (1/4 nautical mile) offshore, depending on the topography of the

site. Strong winds occasionally required flying at higher altitudes or farther offshore, whereas fog

or low cloud ceilings sometimes required flying at a lower altitude or closer inshore. The 1996

survey was divided into two regions, each with separate aircraft and personnel. ADF&G

surveyed Southeast Alaska from Dixon Entrance to Yakutat and the NMFS surveyed the Gulf of

Alaska and Aleutian Islands, from Prince William Sound to Attu Island.

We photographed sea lions using 35-mm manual-focus cameras with motor drives and

zoom lenses (70-210 mm or equivalent) and moderately-fast (e.g., IS0 200) color transparency

(slide) film. Where appropriate, sequential photographs overlapped slightly to guarantee

complete coverage.of a site. NMFS survey personnel also photographed each site using a highresolution 8-mm (HI-8) video camera. Video recordings provided an overview of each site and

served as a backup in case the slides were unusable. In the laboratory, we counted sea lions from

projected images. For the NMFS portion of the survey, the final count of non-pup sea lions for

each rookery or haulout was the mean for two independent counters. If the individual results for

a particular site differed by 10% or more, each person re-counted the sea lion images for that site.

For their portion of the survey, ADF&G had a second, independent counter to verify or detect

errors in results from the original counter. Both survey teams used direct visual counts instead of

photographs for sites with few animals (e.g., 20 or fewer sea lions).
4

Land-Based Pup Surveys

The ADF&G and NMFS counted sea lion pups at nine rookeries from For-rester Island to

Ugamak Island between 27 June and 14 July. The ADF&G survey team counted pups at

For-rester Island, Hazy Island, and White Sisters rookeries in Southeast Alaska, at Seal Rocks and

Fish Island in the eastern Gulf of Alaska, and at Outer Island in the central Gulf of Alaska. NMFS

personnel counted sea lion pups at Marmot and Atkins Islands in the Gulf of Alaska, and Ugamak

Island in the eastern Aleutian Islands. Vessels delivered survey teams to within 2-4 km of a site;

the survey team then went ashore in small boats. For several rookeries, transportation was by

helicopter. After all sea lions other than pups were cleared from the beach, two or three

biologists independently counted live pups on the beach and in the water. The final pup count for

each rookery was the mean of several (typically two or three) independent counts.

Data Analysis

Geographical regions used for analyzing survey results were the same as those used in

previous survey reports (Merrick et al. 1987, Loughlin et al. 1990, Merrick et al. 1991, Merrick

et al. 1992, Sease et al. 1993, Strick et al. 1997) and those adopted by the Steller sea lion

Recovery Plan (NMFS 1992): Southeast Alaska; eastern, central, and western Gulf of Alaska;

eastern, central, and western Aleutian Islands; and the Bering Sea (Fig. 1). The Bering Sea region

contains few haul-out sites and only one rookery (Walrus Island in the Pribilof Islands). We did

not survey the Bering Sea region because of logistical limitations.

Another geographical region used during the analyses of survey data is the Kenai

Peninsula (Outer Island) to Kiska Island index area, which includes four of the smaller regions
5

listed above: the central and western Gulf of Alaska, and the eastern and central Aleutian Islands.

This index area was selected initially because it encompasses what historically has been the center

of the Steller sea lions’ range and includes the major component of the Alaska sea lion population

(Merrick et al. 1987, NMFS 1992). The Kenai to Kiska index area included 59.3% of all non-pup

sea lions counted in 1996 (58.8% on all trend sites and 61.6% on trend rookeries).

Analyses of population trends included subtotals of non-pups at rookery trend sites, all

trend sites (rookeries and haul-out sites), and at all surveyed sites Alaska-wide, for

the Kenai to Kiska index area, and for smaller geographical regions. The number of sites included

in the “all surveyed sites” sub-totals varied slightly between surveys. Virtually all sites that

account for these differences individually contained very few (I 10) sea lions during recent surveys

(1991 and later) and the impact of these differences was negligible. Additional analyses compared

trends for the eastern and western stocks. Overall changes in numbers of non-pups regionally and

in numbers of non-pups and pups at selected rookeries from 1991 to 1996, 1992 to 1996, and

from 1994 to 1996 were expressed as a percentage of the earlier count. We did not attempt to

test the statistical significance of these overall changes, largely because of the difficulty in

determining appropriate variances for the different counts and the resulting complexity of

interpretation. We estimated average annual rate of change from 1990 or 1991 to 1996 from the

slope of a simple linear regression of the natural log of counts on survey year. We tested the null

hypothesis of no trend during the time interval using the significance of the slope for the

regression.

It should be noted that, with the exception of the distinction between the eastern and

western stocks, the geographical divisions between regions are somewhat arbitrary and may not
6

accurately reflect the underlying structure of stocks or other subunits of the population, if they

exist. We present results for each region to identity and highlight varying population trends in the

different regions. However, readers should not think that sea lion populations in one region are

separate and independent of those in other regions.

Alaska State-wide

RESULTS

Aerial Surveys of Non-pups

We counted a total of 41,529 non-pup Steller sea lions on 280 rookery and haul-out sites

from Southeast Alaska through the western Aleutian Islands in 1996 (Table 2). This included

trend sites as well as all other sites. Of these sites, 149 (53%) were occupied by 20 or more nonpups, 26 (9%) included fewer than 20 non-pups, and 105 (38%) were unoccupied. There were

125 sites in the western stock with 20 or more non-pups in 1996 that also were surveyed in, 1994;

66 (53%) declined by 5% or more, 45 (36%) increased by 5% or more, and 14 (11%) changed by

less than 5%. For the eastern stock, 18 sites with 20 or more non-pups in 1996 also were

surveyed in 1994; 10 (55%) declined by 5% or more, 5 (28%) increased by 5% or more, and 3

(17%) changed by less than 5%.

The 1996 count for all surveyed sites was the lowest count for all survey years for which

an equivalent comparison is available: 10.7% lower than the 46,497 non-pups counted in 1991,

9.2% lower than in 1992 (45,750), and 8.0% lower than in 1994 (45,148)(Fig. 2). The estimated

average annual rate of decline for 1991 to 1996 was 2.1% (95% C.I.: +0.4% to -4.6%;

P = 0.067). The non-pup count at 95 trend sites Alaska-wide was 30,454 (Table 2). This was a
7

decline of 18.0% from 1991 (37,133), a 12.6% decline from 1992 (34,844), and a 7.6% decline

from 1994 (32,945)(Fig. 2). The average annual rate of decline was 3.8% (95% C.I.: 2.3% to

5.3%; P = 0.009) for 1991 to 1996. The subtotal for the 33 trend rookeries throughout Alaska

was 22,562 non-pups (Table 2). This represented declines of 18.3% since 1990, 16.1% since

1991 (26,879) 12.7% since 1992 (25,849), and 3.8% since 1994 (23,452)(Fig. 2). The average

annual rate of decline for the trend rookeries was 3.6% (95% C.I.: 2.6% to 4.6%; P = 0.001) for

1990 to 1996.

Comparison of Western and Eastern Stocks

The western stock of Steller sea lions in Alaska includes animals from the eastern Gulf of

Alaska through the western Aleutian Islands. The 1996 western stock count for all surveyed sites

(30,622: Table 3) indicated declines of 17.3% from 1991 (37,048), 14.3% from 1992 (35,747),

and 8.2% from 1994 (33,361). The estimated average annual rate of decline was 3.8% (95% C.I.:

3.2% to 4.4%; P = 0.001) for 1991 to 1996. Overall declines generally were greater for all trend

sites and for trend rookeries than for all surveyed sites (Table 3). The annual rates of decline

from 1990 to 1996 were 5.5% (95% C.I.: 4.5% to 6.5%; P<0.00l) at all trend sites and 5.4%

(95% C.I.: 3.3% to 7.5%; P = 0.004) at trend rookeries (Table 3).

The eastern stock is represented in Alaska only by Southeast Alaska, where we counted

10,907 non-pups at all surveyed sites. Of these, 8,231 were on trend sites (rookeries and

haulouts), and 6,204 at the three trend rookeries (Table 3). Although these 1996 counts indicate

declines of 4.5% (rookery trend sites) to 7.5% (all surveyed sites) from 1994, numbers of nonpups in Southeast Alaska increased during each survey interval from 1989 to 1994 (except at all
8

trend sites from 1991 to 1992). The average annual change in Southeast was positive for trend

sites and for trend rookeries from 1990 to 1996 and for all surveyed sites from 1991 to 1996,

although none of the regressions was significant (P 0.077: Table 3).

Kenai to Kiska Index Area

We counted 24,625 non-pup sea lions at 189 surveyed sites from the Kenai Peninsula to

Kiska Island in 1996, indicating declines of 9.8% from 1991 (27,313), 8.3% from 1992 (26,854),

and 5.3% from 1994 (25,995)(Table 2, Fig. 2). The estimated annual rate of decline was 2.0%

(95% C.I.: 1.2% to 2.9%; P = 0.009) over the 5-year period. In the Kenai to Kiska index area

there are 69 trend sites (26 rookeries and 43 haulouts), where we counted 17,900 non-pup in

1996 (Table 2). This was a decline of 21.3% since 1990 (22,754), of 17.7% since 1991 (21,737),

of 13.4% since 1992 (20,679), and 4.3% since 1994. The estimated average annual rate of

decline at trend sites in the Kenai to Kiska index area was 4.1% (95% C.I.: 3.0% to 5.2%;

P = 0.001) for 1990 to 1996. Similar rates of decline were apparent for the 26 trend rookeries in

the Kenai to Kiska area, where we counted 13,905 non-pup sea lions. This was an overall decline

of 25.6% from 1990 (18,694) of 19.1% from 1991 (17,186), of 16.2% from 1992 (16,589), and

of 4.1% from 1994 (14,505). The average annual rate of decline at the Kenai to Kiska trend

rookeries was 5.0% for 1990 to 1996 (95% C.I.: 3.1% to 6.8%; P = 0.003).

The eastern Aleutian Islands, one of the four subareas making up the Kenai to Kiska index

area, is the only one in which numbers of non-pups increased (7% at trend sites) from 1994 to

1996 (Table 4, Fig. 3a). The greatest observed decline (10% at trend rookeries, 13% at trend

sites, 15% at all surveyed sites) was in the central Gulf of Alaska (Tables 4, 5, and 6; Fig. 3a, 3b,
9

4a). Non-pup counts in the western Gulf of Alaska and central Aleutian Islands regions declined

by 4% to 6% at all trend sites and trend rookeries, and by less than 3% at all surveyed sites.

Subareas Outside the Kenai to Kiska Index Area

One of the three regions outside of the Kenai to Kiska index area, the eastern Gulf of

Alaska, has shown continuous decline during the 1990s for all trend sites (Table 4, Fig.5a), for

trend rookeries (Table 5, Fig. 5b), and for all surveyed sites (Table 6, Fig. 4b). The decline in

non-pup numbers was especially steep from 1994 to 1996: 37% and 35% at all trend sites and all

surveyed sites, respectively. The western Aleutian Islands also have generally declined after

showing an increase from 1990 to 1991. Trends in Southeast Alaska are presented as part of the

comparison of western and eastern stocks, above.

Proportion of Non-nuns on Rookeries

The proportion of non-pup sea lions on rookeries, compared to the numbers of non-pups

on all. surveyed sites, was 0.586 Alaska-wide in 1996 (Table 7). This was an increase of 3.0%

from 1994 (0.569), but was a decline of 4.8% from 1992 (0.615), and a decline of 8.4% from

1991 (0.639). Regionally, the proportion ranged from a low of 0.404 in the eastern Gulf of

Alaska to 0.771 in the western Aleutian Islands (Table 7, Fig. 6). The proportion of non-pups on

rookeries consistently has been lowest in the eastern Gulf of Alaska, where there are only two

rookeries: Seal Rocks and Fish (Wooded) Island. The most noteworthy change in 1996 was that

the proportion of non-pups on rookeries in the eastern Gulf had increased by 25.8% from 1994

after declining from 1991 through 1994. The relative change from 1994 to 1996 in the other
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regions ranged from -4.0% to +5.0%. Note that equivalent versions of this analysis in previous

survey reports compared counts of non-pups on all trend rookeries and on all trend sites.

Included for the 1996 survey report were five non-trend rookeries (Table 7) and about 180 nontrend haul-out sites (Table l), many of which had low or zero counts. Non-pup counts for

individual rookeries are listed in Table 8.

Land-Based Pup Surveys

ADF&G and NMFS counted 6,116 live pups at nine rookeries from Southeast Alaska

through the eastern Aleutian Islands in 1996 (Tables 1 and 9). For Southeast Alaska as a whole,

the 1996 pup count (3,714) increased 3.2% from 1990 (3,600) but declined 1.5% from 1994

(3,77O)(Table 9). Pup counts at the two rookeries in the eastern Gulf of Alaska (Seal Rocks and

Fish Island) declined by 24% to 41% during the same period. We counted pups at only two of

the five rookeries (Outer, Marmot, Sugarloaf, Chowiet, Chirikof Islands) in the central Gulf of

Alaska in 1996. At Marmot Island the number of pups declined 61% from 1991 and 21% from

1994. Pup numbers at Outer Island changed little from 1994 to 1996 after dropping 67% from

1990 to 1994. The 1996 pup counts at Atkins Island in the western Gulf of Alaska and at

Ugamak in the eastern Aleutian Islands declined by 15% to 17% from 1990 but increased by 13%

to 23% compared to 1994.

DISCUSSION

Results of the most recent aerial and land-based surveys of Steller sea lions in Alaska

indicate that declines observed during previous surveys continued through 1996. The population
11

decline was first identified in the eastern Aleutian Islands in the mid- to late 1970s (Braham et al.

1980). From the mid- 1970s through the late 198Os, Steller sea lions declined significantly

throughout the Gulf of Alaska and Aleutian Islands (Met-rick et al. 1987, Loughlin et al. 1990,

Met-rick et al. 1991, Merrick et al. 1992, Sease et al. 1993, Strick et al. 1997). Although the rate

of decline was less severe in some regions of Alaska during the 199Os, the decline in sea lion

numbers Alaska-wide continues at about 4% per year at trend sites.

Population trajectories are very different for the two stocks within the population.

Numbers of non-pups in the eastern stock in Southeast Alaska, approximately one-half of the

entire eastern stock, declined from 1994 to 1996 by about 4.5% at trend sites and 7.5% at all

surveyed sites. Despite this recent decline, the overall trend since 1990 has been increasing by

about 2% to 3% per year. Similarly, pup numbers in Southeast Alaska declined by 1.5% from

1994 but increased by 3.2% relative to 1990. Future surveys will clarity whether any trend is

apparent for sea lions in Southeast Alaska and for the eastern stock in general, or if they remain

relatively stable at the current population level.

The situation is very different for the western stock in Alaska, where the number of nonpups continued to decline at about 5.5% per year for trend sites and trend rookeries and almost

4% per year at all surveyed sites. The rates of decline have been slightly lower for the Kenai to

Kiska index area, largely because the greatest relative declines have been observed in the eastern

Gulf of Alaska, which is not within the index area., At a more regional level, the picture becomes

confused as some regions increased while others decreased, and rates of change also varied. It is

important to employ caution in the interpretation of regional trends, as the boundaries between

the regions are arbitrary (except between the eastern and western stocks), and sea lions certainly
12

do travel between regions, particularly during the winter. That being said, however, it is

noteworthy that the greatest declines from 1994 to 1996 took place in adjacent regions, the

eastern and central Gulf of Alaska, encompassing a wide region from east of Prince William

Sound to the Shumagin Islands. We do not have pup counts from enough rookeries in the

western stock to corroborate or contradict these observed trends in non-pup numbers.
13

ACKNOWLEDGMENTS

We gratefully acknowledge pilots Dan Vollum and Alan Williams of Aero Air, Hillsboro,

Oregon (1998), and Ken Bellows of BellAir Inc. of Sitka, Alaska, for transportation in the aerial

surveys. We thank the crew of the R/VMedeia for the vessel-supported pup counts in Southeast

Alaska, and the crew of the U.S. Fish and Wildlife Service vessel M/V Tiglax for their support in

the Aleutian Islands. Tom Walters of Maritime Helicopters, Kodiak, Alaska, and the U.S. Coast

Guard, Sitka Air Station supplied helicopter transportation for pup counts at Marmot Island and

in Southeast Alaska, respectively. We greatly appreciate the wide-ranging assistance from

personnel of the Alaska Maritime National Wildlife Refuge in Homer, Alaska, and especially Jeff

Williams and the staff at the refuge’s Aleutian Islands Unit on Adak Island. The staff of the

Izembek National Wildlife Refuge provided lodging and logistic support in Cold Bay, Alaska. K.

Wynne (Alaska SeaGrant) and L. Fritz (NMFS) participated in the Gulf of Alaska/Aleutian

Islands aerial survey. C. Rice and B. Taylor (ADF&G) assisted in the aircraft and during

counting, respectively, for the Southeast Alaska survey. K. Chumbley, C. Hutchinson, L. Rea,

and J. Thomason of NMFS and W. Cunningham, D. McAllister, K. Pitcher, and U. Swain of

ADF&G participated in pup counts. C. Gburski, L. LaFrance, and A. Tiplady helped proofread

the tables. G. Duker and J. Lee provided editorial support. Additional comments from B.

Hanson, S. Melin, T. Loughlin, J. Thomason, and A. York, improved the manuscript. We

conducted these surveys under the authority of NMFS Marine Mammal Protection Act Permit

No. 809 and Special Use Permit No. 5 1576 from the Alaska Maritime National Wildlife Refuge.
14

LITERATURE CITED

Bickham, J.W., J.C. Patton, and T.R. Loughlin. 1996. High variability for control-region

sequences in a marine mammal--implications for conservation and biogeography of Steller

sea lion (Eumetopias jubatus). J. Mammal. 77195-108.

Braham, H.W., R.D. Everitt, and D.J. Rugh. 1980. Northern sea lion population decline in the

eastern Aleutian Islands. J. Wildl. Manage. 44:25-33.

Calkins, D.G. and K.W. Pitcher. 1982. Population assessment, ecology and trophic relationships

of Steller sea lions in the Gulf of Alaska. Alaska Department of Fish and Game, Final

Report RU243. Alaska Department of Fish and Game, 333 Raspberry Road, Anchorage,

Alaska 99502, 76 pp.

Loughlin, T.R. 1997. Using the phylogeographic method to identify Steller sea lion stocks,

pages 159-171. In A.E. Dizon, S.J. Chivers, and W.F. Perrin (editors), Molecular

genetics of marine mammals. Soc. Mar. Mammal., Spec. Publ. No. 3.

Loughlin, T.R., A.S. Perlov, and V.A. Vladimirov. 1990. Survey of northern sea lions

(Eumetopias jubatus) in the Gulf of Alaska and Aleutian Islands during June 1989. U.S.

Dep. Commer., NOAA Tech. Memo. NMFS F/NWC-176,26 pp.

Loughlin, T.R., A.S. Perlov, and V.A. Vladimirov. 1992. Range-wide survey and estimation of

total number of Steller sea lions in 1989. Mar. Mammal Sci. 8:220-239.

Loughlin, T.R., D.J. Rugh, and C.H. Fiscus. 1984. Northern sea lion distribution and abundance:

1956-80. J. Wildl. Manage. 48:729-740.

Merrick, R.L., D.G. Calkins, and D.C. McAllister. 1992. Aerial and ship-based surveys of Steller

sea lions in Southeast, Alaska, the Gulf of Alaska, and Aleutian Islands during June and

July 1991. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-l, 37 pp.

Merrick, R.L., L.M. Ferm, R.D. Everitt, R.R. Ream, and L.A. Lessard. 199 1. Aerial and shipbased surveys of northern sea lions, (Eumetopias jubatus) in the Gulf of Alaska and

Aleutian Islands during June and July 1990. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS F/NWC-196,34 pp.

Merrick, R.L., T.R. Loughlin, and D.G. Calkins. 1987. Decline in abundance of the northern sea

lion, Eumetopias jubatus, in Alaska, 1956-86. Fish. Bull., U.S. 85:351-365.

NMFS (National Marine Fisheries Service). 1992. Recovery plan for the Steller sea lion

(Eumetopias jubatus). Prepared by the Steller Sea Lion Recovery Team for the National

Marine Fisheries Service, Silver Spring, Maryland, 92 pp.
15

Sease, J.L., J.P. Lewis, D.C. McAllister, R.L. Merrick and S.M. Mello. 1993. Aerial and shipbased surveys of Steller sea lions (Eumetopias jubatus) in Southeast Alaska, the Gulf of

Alaska, and Aleutian Islands during June and July 1992. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS F/NWC-17, 57 pp.

Strick, J.M., L.W. Fritz, and J.P. Lewis. 1997. Aerial and ship-based surveys of Steller sea lions

(Eumetopias jubatus) in Southeast Alaska, the Gulf of Alaska, and Aleutian Islands during

June and July 1994. U.S. Dep. Commer., NOAA Tech. Memo. NMFS F/NWC-71, 55 pp.
16

Table l.--Counts of adult and juvenile (non-pup) Steller sea lions at rookery (*) and haul-out sites

in Alaska during June and July 1996. Trend sites (+) are those sites used for analyses of

trends in survey counts. Count types are photographic (P) or visual (V). Sites are

arranged approximately in geographical order from Dixon Entrance in Southeast Alaska to

Attu Island in the western Aleutian Islands.
17

Table 1 .--Non-pup and pup counts - 1996, continued.

Subtotals for Southeast Alaska

All 58 sites (pups at 3 rookeries)

13 trend rookery and haul-out sites

3 trend rookery sites
18

Table l.--Non-pup and pup counts - 1996, continued.

Subtotals for the Eastern Gulf of Alaska

All 25 sites (pups at 2 rookeries)

9 trend rookery and haul-out sites’

1 trend rookery site
19

Table l.--Non-pup and pup counts - 1996, continued.
20

Table l.--Non-pup and pup counts - 1996, continued
21

Table l.--Non-pup and pup counts - 1996, continued.

366
22

Table l.--Non-pup and pup counts - 1996, continued.
23

Table l.--Non-pup and pup counts - 1996, continued.
24

Table l.--Non-pup and pup counts - 1996, continued.
25

Table l.--Non-pup and pup counts - 1996, continued.
26

Table l.--Non-pup and pup counts - 1996, continued.

1

 Trend Site at Sitkagi Bluffs was not surveyed in 1996 in the eastern Gulf of Alaska

2

 Two Trend Rookeries on Agattu Island previously reported as one Trend Rookery site
27

Table 2.--Counts of adult and juvenile (non-pup) Steller sea lions observed at trend rookeries, at

all trend sites (rookeries and haul-outs), and at all surveyed sites in the Kenai to Kiska

index area and Alaska state-wide for June and July aerial surveys, 1990 to 1996, including

number of sites (n), and estimated annual rate of change with upper and lower limits of the

95% confidence interval and significance (P) from linear regression (see text).

1

 “inc.” indicates incomplete survey data.
28

Table 3 .--Counts of adult and juvenile (non-pup) Steller sea lions from the eastern and western

stocks in Alaska at trend rookeries, at all trend sites (rookeries and haul-outs), and at all

surveyed sites during June and July aerial surveys from 1990 to 1996, including number of

sites in each region (n) and estimated annual rate of change with upper and lower limits for

the 95% confidence interval and significance (P) from linear regression (see text).

1

 “inc.” indicates incomplete survey data.
Table 4.--Counts of adult and juvenile (non-pup) Steller sea lions observed at ROOKERY AND HAUL-OUT TREND SITES in

seven subareas of Alaska during June and July aerial surveys from 1990 to 1996, including number of trend sites in each

region (n).
Table 5.--Counts of adult and juvenile (non-pup) Steller sea lions observed at ROOKERY TREND SITES in seven subareas of

Alaska during June and July aerial surveys from 1990 to 1996, including number of trend rookeries in each region (n).
Table 6.--Counts of adult and juvenile (non-pup) Steller sea lions observed at ALL SURVEYED ROOKERY AND HAUL-OUT

SITES in seven subareas of Alaska during June and July aerial surveys from 1991 to 1996. The number of sites for each

region (n) is for the 1996 survey (see text).
Table. 7--Proportion of adult and juvenile (non-pup) Steller sea lions on rookeries, compared to numbers of non-pups on all

surveyed sites, in seven subareas of Alaska during June and July aerial surveys from 1991 to 1996. Subtotals include

counts for five non-trend rookeries, as indicated in the footnotes, as well as all non-trend haul-out sites listed in Table 1

and in Merrick et al. (1992), Sease et al. (1993), and Strick et al. (1997). [Note: the equivalent versions of this table

for survey reports from 1994 and earlier included only trend rookeries and haul-out sites.]
33

Table S.--Counts of adult and juvenile (non-pup) Steller sea lions at principal rookeries in Alaska

for 1991 though 1996, including overall percent change (A 1996) between the count for

each year and the count for 1996.
34

Table S.--Non-pup counts at principal rookeries, 199l- 1996, continued.
35

Table 8 .--Non-pup counts at principal rookeries, 199l- 1996, continued.
36

Table 8.--Non-pup counts at principal rookeries, 1991-1996, continued
37

Table 9.--Counts of Steller sea lion pups at rookeries in Alaska during June and July surveys from

1990, 1994, and 1996, including the percent change ( 1996) from the earlier counts to the

1996 counts.
38

Figure 1 .--Map of Alaska, showing seven geographical regions used for analyses of aerial survey

results and major rookeries, as modified from Merrick et al. (1987).
39

Figure 2.--Counts of non-pup (adult and juvenile) Steller sea lions at all surveyed sites, all trend

sites (rookeries and major haulouts), and trend rookeries for Alaska state-wide and for the

Kenai Peninsula to Kiska Island index area, 1970s to 1996. All counts are from aerial

surveys.
Figure 3.--Numbers of non-pup (adult and juvenile) Steller sea lions counted on trend rookery and

haul-out sites (A) and on trend rookery sites (B) in the Kenai to Kiska index area, by

region, 1990 to 1996.
41

Figure 4.--Numbers of non-pup (adult and juvenile) Steller sea lions counted on all surveyed sites

in the regions within (A) and outside of(B) the Kenai to Kiska index area, 1990 to 1996.
42

Figure 5.---Numbers of non-pup (adult and juvenile) Steller sea lions counted on trend rookery

and haul-out sites (A) and on trend rookery sites (B) in regions outside of the Kenai to

Kiska index area, 1990 to 1996.
43

Figure 6.--Proportions of non-pup (adult and juvenile) Steller sea lions located on rookeries,

compared to numbers of non-pups on all surveyed sites, by region, 1991 to 1996. Counts

include five rookeries and about 180 haulouts that are not trend sites, as listed in Tables 1

and 7.
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AFSC98 LAUTH, R. R. 1999. The 1997 Pacific West Coast upper continental slope trawl survey of groundfish

resources off Washington, Oregon, and California: Estimates of distribution, abundance, and length

composition, 284 p. NTIS No. PB99-133043.

97 HILL, P. S., and D. P. DEMASTER. 1998. Alaska marine mammal stock assessments, 1998, 166 p. NTIS

No. PB99-130791.

96 WING, B. L., M. M. MASUDA, C. M. GUTHRIE III, and J. H. HELLE. 1998. Some size relationships and

genetic variability of Atlantic salmon (Salmo salar) escapees captured in Alaska fisheries, 1990-95, 32 p.

NTIS No. PB99-118697.

95 ORR, J. W., M. A. BROWN, and D. C. BAKER. 1998. Guide to rockfishes (Scorpaenidae) of the genera

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114217.

94 THROWER, F., R. MARTIN, and R. HEINTZ. 1998. Effect of seawater entry date on 24-hour plasma

sodium concentration and survival of juvenile spring chinook salmon (Oncorhynchus tshawytscha) reared

in marine net-pens, 18 p. NTIS No. PB98-173545.

93 MURPHY, J. M., N. E. MALONEY, and B. L. WING. 1998. Distribution and abundance of zooplankton

in the north Pacific Subarctic Frontal Zone and adjacent water masses, 31 p. NTIS No. PB98-159163.

92 FRITZ, L. W., and S. A. LOWE. 1998. Seasonal distributions of Atka mackerel ( Pleurogrammus

monopterygius) in commercially-fished areas of the Aleutian Islands and Gulf of Alaska, 29 p. NTIS No.

PB98-153703.

91 WING, B. L., and J. J. PELLA. 1998. Time series analyses of climatological records from Auke Bay,

Alaska, 90 p. NTIS No. PB98-149206.

90 PACUNSKI, R. E., P. A. LIVINGSTON, and B. S. MILLER. 1998. Food of flathead sole Hippoglossoides

elassodon in the eastern Bering Sea, 27 p. NTIS No. PB98-148679. 

89 WILKINS, M. E., M. ZIMMERMANN, and K. L. WEINBERG. 1998. The 1995 Pacific west coast bottom

trawl survey of groundfish resources: Estimates of distribution, abundance, and length and age

composition, 138 p. plus Appendices. NTIS No. PB98-136252.

88 FRITZ, L. W., A. GREIG, and R. F. REUTER. 1998. Catch-per-unit-effort, length, and depth distributions

of major groundfish and bycatch species in the Bering Sea, Aleutian Islands, and Gulf of Alaska regions

based on groundfish fishery observer data, 179 p. NTIS No. PB98-139298.

87 SINCLAIR, E. H. (editor) 1997. Fur seal investigations, 1996, 115 p. NTIS No. PB98-131790.

86 SINCLAIR, E.H. (editor). 1997. Fur seal investigations, 1995, 188 p. NTIS No. PB98-131808.

85 KINOSHITA, R. K., A. GREIG, and J. M. TERRY. 1998. Economic status of the groundfish fisheries off

Alaska, 1996, 91 p. NTIS No. PB98-126170.

84 LAAKE, J., D. RUGH, and L. BARAFF. 1998. Observations of harbor porpoise in the vicinity of acoustic

alarms on a set gill net, 40 p. NTIS No. PB98-117641.