historical and contemporary diet of northern fur … · historical and contemporary diet of...
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Historical and contemporary diet of northern fur seals in the North Pacific
Rolf R. Ream and Tonya K. ZeppelinNational Marine Mammal Laboratory
Overview
• Summarize at-sea diet using multi-national historical data sets
• Describe contemporary food habits from U.S. islands
• Address spatial and temporal variability in diet
Robben Island
Kuril Islands
Commander Islands
Bogoslof Island
Pribilof Islands
San Miguel Island
Russia North America
Northern fur seal distribution and breeding sites
Food Habits Data Sources
• Historical: pelagic collections (stomachs)– Japan– Russia– United States
• Contemporary: breeding islands (scats and spewings)– United States
• Percent occurrence (PO) of prey =% of samples w/ prey “X” out of all samples w/ prey
– “Primary” prey
Pelagic DataSpatial and Temporal Coverage
• Japan– Western North Pacific (January-June, 1953-1991)
• Russia– Commander Islands (June-November, 1965-1982)– Sea of Okhotsk (June-August, 1964-1981)– Sea of Japan (February-May, 1961-1976)
• United States (ranging from 1958-1974)– California (February-May, 1958-1966)– Washington/Oregon (February-May, 1958-1972)– British Columbia (February-May, 1958-1968)– Gulf of Alaska (February-May, 1958-1968)– Bering Sea (August-September, 1960-1974)
Japanese and Russian Pelagic Collections
Japan - Top four prey
Japanese collections (Jan-June, n=4029)
0
5
10
15
20
Lantern fish Japanese fireflysquid
Mackerels andtunas
Japanes sardine
Perc
ent o
ccur
renc
e
Japanese Collections
010
2030
4050
6070
8090
1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991
Perc
ent O
ccur
renc
e
Lantern fish Japanese firefly squidMackerels and tunas Japanes sardine
Russia - Top five prey by region
Commander Islands (June-November, n = 561)
0
10
20
30
Walleye pollock Salmon Hexagrammidae(Atka mackerel)
Pacif ic sandlance
Berryteuthismagister
Perc
ent o
ccur
renc
e
Sea of Okhotsk(June-August, n = 204)
0
10
20
30
40
50
Walleyepollock
Salmon Gonatusfabricii
Myctophidae Berryteuthismagister
Perc
ent o
ccur
renc
e
Sea of Japan (February-May, n= 1132)
01020304050607080
Walleye pollock Berryteuthismagister
Perc
ent o
ccur
renc
e
PO by year
Commander Islands (June-November, n = 561)
0
10
20
30
Walleye pollock Salmon Hexagrammidae(Atka mackerel)
Pacif ic sandlance
Berryteuthismagister
Perc
ent o
ccur
renc
e
Sea of Japan (February-May, n= 1132)
01020304050607080
Walleye pollock Berryteuthismagister
Perc
ent o
ccur
renc
e
Commander Islands
0
10
20
30
40
50
60
70
80
1965 1967 1969 1971 1973 1975 1977 1979 1981Pe
rcen
t Occ
urre
nce
Walleye pollock SalmonHexagrammidae (Atka mackerel) Pacific sand lanceBerryteuthis magister
Sea of Japan
0102030405060708090
100
1961 1963 1965 1967 1969 1971 1973 1975
Perc
ent O
ccur
renc
e
Walleye pollock Berryteuthis magister
PO by yearCommander Islands
0
10
20
30
40
50
60
70
80
1965 1967 1969 1971 1973 1975 1977 1979 1981Pe
rcen
t Occ
urre
nce
Walleye pollock SalmonHexagrammidae (Atka mackerel) Pacific sand lanceBerriteuthis magister
Commander Islands (June-November, n = 561)
0
10
20
30
Walleye pollock Salmon Hexagrammidae(Atka mackerel)
Pacif ic sandlance
Berriteuthismagister
Perc
ent o
ccur
renc
e
Sampling:
• location
• month
Sea of Japan (February-May, n= 1132)
01020304050607080
Walleye pollock Berryteuthismagister
Perc
ent o
ccur
renc
e
Sea of Japan
0102030405060708090
100
1961 1963 1965 1967 1969 1971 1973 1975
Perc
ent O
ccur
renc
e
Walleye pollock Berryteuthis magister
U.S. Pelagic Collections(n=7,933)
U.S. - Top five prey or >10% POby region during winter migration (February-May)
California (n=2097)
0
10
20
30
40
Pacif ic hake Northernanchovy
Market squid Clubhooksquid
Pacif ic saury
Perc
ent O
ccur
renc
e
Washington/Oregon (n=2670)
0
10
20
Pacif icherring
Northernanchovy
Marketsquid
Clubhooksquid
Gonatidsquid
Rockfish
Perc
ent O
ccur
renc
e
British Columbia, Canada (n=382)
0
10
20
30
40
Pacificherring
Sablefish Salmon Walleyepollock
Gonatidsquid (B.magister)
Perc
ent O
ccur
renc
e
Gulf of Alaska (n=968)
0
10
20
30
40
Pacif icherring
Pacif ic sandlance
Capelin Walleyepollock
Gonatidsquid
Perc
ent O
ccur
renc
e
PO by month (all years combined)
California (n=2097)
0
10
20
30
40
Pacif ic hake Northernanchovy
Market squid Clubhooksquid
Pacif ic saury
Perc
ent O
ccur
renc
e
Washington/Oregon (n=2670)
0
10
20
Pacif icherring
Northernanchovy
Marketsquid
Clubhooksquid
Gonatidsquid
Rockfish
Perc
ent O
ccur
renc
e
California
0
10
20
30
40
50
60
Feb(n=1006)
March(n=558)
April(n=268)
May(n=265)
Perc
ent O
ccur
renc
e
Pacific hake
Northernanchovy
Market squid
Clubhooksquid
Pacific saury
Washington/Oregon
0
10
20
30
40
50
Feb(n=257)
March(n=583)
April(n=1181)
May(n=649)
Perc
ent O
ccur
renc
e
PacificherringNorthernanchovyMarket squid
ClubhooksquidGonatidsquidRockfish
PO by month (all years combined)
British Columbia, Canada (n=382)
0
10
20
30
40
Pacif icherring
Sablefish Salmon Walleyepollock
Gonatidsquid (B.magister)
Perc
ent O
ccur
renc
e
Gulf of Alaska (n=968)
0
10
20
30
40
Pacif icherring
Pacific sandlance
Capelin Walleyepollock
Gonatidsquid
Perc
ent O
ccur
renc
e
Gulf of Alaska
0102030405060708090
100
Feb (n=33)
March(n=205)
April(n=225)
May(n=505)
Perc
ent O
ccur
renc
e
Pacificherring
Pacific sandlance
Capelin
Walleyepollock
Gonatidsquid
British Columbia
0
10
20
30
40
50
60
Feb (n=89)
March(n=79)
April (n=44)
May (n=170)
Perc
ent O
ccur
renc
e
Pacificherring
Sablefish
Salmon
Walleyepollock
Gonatidsquid
Washington/Oregon (n=2670)
0
10
20
Pacificherring
Northernanchovy
Marketsquid
Clubhooksquid
Gonatidsquid
Rockfish
Perc
ent O
ccur
renc
e
California
0
10
20
30
40
50
60
1958 1960 1962 1964 1966Pe
rcen
t Occ
urre
nce
Pacific hake Northern anchovyMarket squid Clubhook squidPacific saury
Washington/Oregon
0
10
20
30
40
50
60
1958 1960 1962 1964 1966 1968 1970 1972
Perc
ent O
ccur
renc
e
Pacific Herring Northern anchovy Market squidClubhook squid Gonatid squid Rockfish
PO by year (all months combined)
California (n=2097)
0
10
20
30
40
Pacif ic hake Northernanchovy
Market squid Clubhooksquid
Pacif ic saury
Perc
ent O
ccur
renc
e
PO by year (all months combined)
British Columbia, Canada (n=382)
0
10
20
30
40
Pacif icherring
Sablefish Salmon Walleyepollock
Gonatidsquid (B.magister)
Perc
ent O
ccur
renc
e
Gulf of Alaska (n=968)
0
10
20
30
40
Pacif icherring
Pacific sandlance
Capelin Walleyepollock
Gonatidsquid
Perc
ent O
ccur
renc
e
Gulf of Alaska
0
10
20
30
40
50
60
70
1958 1960 1962 1964 1966 1968
Perc
ent O
ccur
renc
e
Pacific herring Pacific sand lanceCapelin Walleye pollockGonatid squid
British Columbia, Canada
0102030405060708090
100
1958 1960 1962 1964 1966 1968
Perc
ent O
ccur
renc
e
Pacific herring SablefishSalmon Walleye pollockGonatid squid (B. magister)
Top 5 prey during summer (August-September) in the Bering Sea
Bering Sea (n=1816)
0
10
20
30
40
50
60
Greenlandturbot
Bathylagidae Capelin Walleyepollock
Gonatidsquid
Perc
ent O
ccur
renc
e
Bering Sea
0102030405060708090
100
1960 1962 1964 1966 1968 1970 1972 1974
Perc
ent O
ccur
renc
e
Greenland turbot BathylagidaeCapelin Walleye pollockGonatid squid
Breeding IslandsSpatial and Temporal Coverage
• Pribilof Islands, AK– 1987-2000
• Bogoslof Island, AK– 1997-2000
• San Miguel Island, CA– 1980-1986
• Scats and spewings
Pribilof IslandsTop five prey by island (August-September)
St. Paul Island (n=2970)
0
10
20
30
40
50
60
70
Walleyepollock
Gm/Gm squid Pacif ic sandlance
Salmon Gb/Bm squid
Perc
ent O
ccur
renc
e
St. George Island (n=1203)
0
10
20
30
40
50
60
70
Walleyepollock
Gm/Gm squid Northernsmoothtongue
Salmon Gb/Bm squid
Perc
ent O
ccur
renc
e
St. Paul Island
0102030405060708090
100
1987 1989 1991 1993 1995 1997 1999
Perc
ent O
ccur
renc
e
Walleye pollock Gm/Gm squidPacific sand lance SalmonGb/Bm squid
St. George Island
0102030405060708090
1987 1989 1991 1993 1995 1997 1999
Perc
ent O
ccur
renc
eWalleye pollock Gm/Gm squidNorthern smoothtongue SalmonGb/Bm squid
Bogoslof and San Miguel Islands Top 5 prey or > 10% PO
Bogoslof Island (n=148)
0102030405060708090
Northernsmoothtongue
Gb/Bm squid Gonatus tinro Walleyepollock
Northernlampfish
Perc
ent O
ccur
renc
e
San Miguel Island, CA (n=518)
0
10
20
30
Pacif ic hake Marketsquid
Clubhooksquid
Californialanternfish
Northernanchovy
Juvenilerockfish
Perc
ent O
ccur
renc
e
San Miguel Island
0
10
20
30
40
50
60
70
1980 1982 1984 1986
Perc
ent O
ccur
renc
e
Pacific hake Market squidClubhook squid California lanternfishNorthern anchovy Juvenile rockfish
(1997-2000)
Polovina CliffsPolovina
VostochniMorjovi
LukaninKitovi
ZapadniLittle ZapadniZapadniReef Tolstoi
GorbatchArdiguen
Reef
South
Zapadni
East CliffsEast Reef
North
Staraya Artil
Foraging areas and dietPribilof Islands
119 119 trips made by 97 trips made by 97 females, 1995females, 1995--9696
Polovina CliffsPolovina
VostochniMorjovi
LukaninKitovi
ZapadniLittle ZapadniZapadni Reef
Tolstoi
GorbatchArdiguen
Reef
South
Zapadni
East CliffsEast Reef
North
Staraya Artil
Rookery complexes based on diet (1987-2000)
Pribilof Islands spewing-scat comparison Species composition
St. George Island
0
10
20
30
40
50
60
70
80
Gb/Bm
Gm/Gm
Northe
rn Smoo
thton
gue
Pacific
Herr
ing
Pacific
salm
on
Pacific
Sand L
ance
Walley
e Poll
ock
Perc
ent o
ccur
renc
e Scats (n=1,127)
Spews (n=204)
St. Paul Island
0
10
20
3040
50
60
70
80
Gb/Bm
Gm/Gm
Northe
rn Smoo
thton
gue
Pacific
Herr
ing
Pacific
salm
on
Pacific
Sand L
ance
Walley
e Poll
ock
Perc
ent o
ccur
renc
e Scats (n=2,317)
Spews (n=63)
Pribilof Islands spewing-scat comparison Walleye pollock age class distribution
St. George
0
10
20
30
40
50
60
70
80
0 1 2 3 4 5
Age Class
FO
Scats (n=1,484 otoliths in 173 samples)
Spews (n=105 otoliths in 27 samples)
St. Paul
0
10
20
30
40
50
60
70
80
0 1 2 3 4 5
Age Class
FO
Scats (n=17,827 otoliths in 902 samples)
Spews (n=154 otoliths in 23 samples)
Northern fur seal diet• Fur seal distribution extensive = wide range of
prey consumed• Within regions, diversity of prey is low• Prey composition differed among regions• Affected by the habitat used within a region• Variable over months and years, some trends• Effects of regime shifts?
– 1977, 1989, 1999 (?)– Diet data encompassing periods both before and after
these events is limited
Bering Sea and Pribilof Islands Historical vs. contemporary data
Pelagic data• 1960-1974• Stomachs (n=1,816)• Top prey:
Gonatid squidCapelin
Walleye pollockGreenland turbot
Bathylagidae
Breeding Islands• 1987-2000 • Scats (n=4,178)• Top prey:
Walleye pollockGonatid squid
SalmonSand Lance
Northern smoothtongue
Bering Sea and Pribilof Islands Historical vs. contemporary data
• Potential differences and biases in methods– Last meal, differential digestion, introduction of
secondary prey, etc. for scats– Not likely to explain current:
• Absence of capelin and Greenland turbot• Large increase in PO of walleye pollock
• Opportunistic predators; possibly affected by 1977 and 1989 regime shifts
• Other evidence of environmental signals?
Japanese pelagic data and the1977 and 1989 regime shifts
Japanese Collections
0
10
20
30
40
50
60
70
80
90
1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991
Perc
ent O
ccur
renc
e
Lantern fish Japanese firefly squidMackerels and tunas Japanes sardine
-2.5
-1.5
-0.5
0.5
1.5
2.5
1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991
PDO
Inde
x
PDO Index
Signals of environmental change in northern fur seal diet
• Effects of regime shifts not conclusive with limited data
• El Nino events are known to change food habits dramatically for pinnipeds– Affect fur seals:
• San Miguel Island breeding colony• Seasonal migrants to the west coast of U.S.
AcknowledgementsAcknowledgements
•• NorihisaNorihisa BabaBabaFisheries Research Agency, JapanFisheries Research Agency, Japan
•• ShirohShiroh YonezakiYonezakiNational Research Institute of Far Seas Fisheries, JapanNational Research Institute of Far Seas Fisheries, Japan
•• Jim ThomasonJim ThomasonNational Marine Mammal Laboratory, USANational Marine Mammal Laboratory, USA