Historical and Contemporary Diet of Northern Fur Seals in the North Pacific

Historical and contemporary diet of northern fur seals in the North Pacific

Rolf R. Ream and Tonya K. Zeppelin National 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 Northern fur seal distribution and breeding sites

Russia North America

Commander Islands

Robben Island Pribilof Islands

San Miguel Island Bogoslof Island

Kuril Islands 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 Data Spatial 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)

20 e

5 Percent occurrenc Percent 0 Lantern fish Japanese firefly Mackerels and Japanes sardine squid tunas

Japanese Collections Lantern fish Japanese firefly squid 90 Mackerels and tunas Japanes sardine 80 70 60 50 40 30 20 Percent Occurrence 10 0 1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 Russia - Top five prey by region

Commander Islands Sea of Okhotsk (June-November, n = 561) (June-August, n = 204)

30 50 40 20 30

20 10 10 0 0 Percent occurrence Percent occurrence Walleye pollock Salmon Hexagrammidae Pacific sand Berryteuthis Walleye Salmon Gonatus Myctophidae Berryteuthis (Atka mackerel) lance magister pollock fabricii magis ter

Sea of Japan (February-May, n= 1132)

80 70 60 50 40 30 20 10 0 Percent occurrence Walleye pollock Berryteuthis magister PO by year

Commander Islands Commander Islands Walleye pollock Salmon (June-November, n = 561) Hexagrammidae (Atka mackerel) Pacific sand lance 80 Berryteuthis magister 30 70

20 60 50 10 40

Percent occurrence 30 Walleye pollock Salmon Hexagrammidae Pacific sand Berryteuthis (Atka mackerel) lance magister 20 Percent Occurrence 10 0 1965 1967 1969 1971 1973 1975 1977 1979 1981

Sea of Japan Sea of Japan (February-May, n= 1132) Walleye pollock Berryteuthis magister

80 100 70 90 60 50 80 40 70 30 20 60 10 0 50 Percent occurrence Walleye pollock Berryteuthis 40 magister 30

Percent Occurrence 20 10 0 1961 1963 1965 1967 1969 1971 1973 1975 PO by year

Commander Islands Commander Islands Walleye pollock Salmon (June-November, n = 561) Hexagrammidae (Atka mackerel) Pacific sand lance 80 Berriteuthis magister 30 70 60 20 50 10 40 0 30 Percent occurrence Walleye pollock Salmon Hexagrammidae Pacific sand Berriteuthis (Atka mackerel) lance magister 20 Percent Occurrence 10 0 1965 1967 1969 1971 1973 1975 1977 1979 1981

Sea of Japan Sea of Japan (February-May, n= 1132) Walleye pollock Berryteuthis magister Sampling:

80 100 70 90 60 • location 50 80 40 70 30 20 60 10 •month 0 50 Percent occurrence Walleye pollock Berryteuthis 40 magister 30

Percent Occurrence 20 10 0 1961 1963 1965 1967 1969 1971 1973 1975 U.S. Pelagic Collections (n=7,933) U.S. - Top five prey or >10% PO by region during winter migration (February-May)

California (n=2097) British Columbia, Canada (n=382)

40 40

30 30 20 20 10 10 0 Percent Occurrence

Percent Occurrence 0 Pac if ic Sablefish Salmon Walleye Gonatid Pacific hake Northern Market squid Clubhook Pacific saury herring pollock squid (B. anchovy squid magister)

Washington/Oregon (n=2670) Gulf of Alaska (n=968)

20 40

10 20

10 Percent Occurrence 0 Percent Occurrence 0 Pac if ic Northern Mar ket Clubhook Gonatid Rockf is h Pac if ic Pacific sand Capelin Walleye Gonatid herring anchovy squid squid squid herring lance pollock squid PO by month (all years combined)

California Pacific hake 60

California (n=2097) 50 Northern anchovy 40 40

30 30 Market squid

20 20 10 Clubhook 10 squid Percent Occurrence Percent Percent Occurrence 0 Pacific hake Northern Market squid Clubhook Pacific saury 0 Pacific saury anchovy squid Feb March April May (n=1006) (n=558) (n=268) (n=265)

Washington/Oregon Pacific Washington/Oregon (n=2670) 50 herring

40 Northern 20 anchovy 30 Market squid 10 20 Clubhook squid Percent Occurrence 0 10 Pac if ic Northern Mar ket Clubhook Gonatid Rockfish Gonatid Percent Occurrence Percent herring anchovy squid squid squid 0 squid Feb March April May Rockfish (n=257) (n=583) (n=1181) (n=649) PO by month (all years combined)

British Columbia 60 Pacific herring British Columbia, Canada (n=382) 50 Sablefish 40 40 30 30 Salmon 20

20 10

Walleye 0 Percent Occurrence 10 Pac if ic Sablefish Salmon Walleye Gonatid Percent Occurrence Percent pollock herring pollock squid (B. 0 Gonatid magis ter ) Feb March April May squid (n=89) (n=79) (n=44) (n=170)

Gulf of Alaska Pacific 100 herring Gulf of Alaska (n=968) 90 80 Pacific sand 70 lance 40 60 30 50 Capelin 20 40 30 10 Walleye

20 Percent Occurrence pollock 0 Percent Occurrence Percent 10 Pac if ic Pacific sand Capelin Walleye Gonatid herring lance pollock squid 0 Gonatid Feb March April May squid (n=33) (n=205) (n=225) (n=505) PO by year (all months combined)

California

California (n=2097) Pacific hake Northern anchovy Market squid Clubhook squid 60 Pacific saury 40

30 50

20 40

10 30

Percent Occurrence 0 20 Pacific hake Northern Market squid Clubhook Pacific saury anchovy squid Percent Occurrence 10

0 1958 1960 1962 1964 1966

Washington/Oregon Pacific Herring Northern anchovy Market s quid Washington/Oregon (n=2670) 60 Clubhook squid Gonatid squid Rockfish

20 50

40 10 30

20 Percent Occurrence 0

Pac if ic Northern Mar ket Clubhook Gonatid Rockfish Percent Occurrence herring anchovy squid squid squid 10

0 1958 1960 1962 1964 1966 1968 1970 1972 PO by year (all months combined)

British Columbia, Canada Pacific herring Sablefish Salmon Walleye pollock British Columbia, Canada (n=382) Gonatid squid (B. magister) 100 90 40

80 30 70 20 60 50 10 40 0 Percent Occurrence 30 Pac if ic Sablefish Salmon Walleye Gonatid herring pollock squid (B. 20 Percent Occurrence magis ter ) 10 0 1958 1960 1962 1964 1966 1968

Gulf of Alaska Pacific herring Pacific sand lance Gulf of Alaska (n=968) Capelin Walleye pollock Gonatid squid 70 40 60 30 50 20 40 10 30

Percent Occurrence 0 20 Pac if ic Pacific sand Capelin Walleye Gonatid

Percent Occurrence herring lance pollock squid 10

0 1958 1960 1962 1964 1966 1968 Top 5 prey during summer (August-September) in the Bering Sea

Bering Sea (n=1816) 60 50 40 30 20

10 Percent Occurrence 0 Greenland Bathylagidae Capelin Walleye Gonatid turbot pollock squid

Bering Sea Greenland turbot Bathylagidae Capelin Walleye pollock 100 Gonatid squid 90 80 70 60 50 40 30

Percent Occurrence 20 10 0 1960 1962 1964 1966 1968 1970 1972 1974 Breeding Islands Spatial and Temporal Coverage • Pribilof Islands, AK – 1987-2000 • Bogoslof Island, AK – 1997-2000 • San Miguel Island, CA – 1980-1986

• Scats and spewings Pribilof Islands Top five prey by island (August-September) St. Paul Island (n=2970) St. Paul Island Walleye pollock Gm/Gm squid 70 100 Pacific sand lance Salmon 60 Gb/Bm squid 90 50 80 40 70 30 60 20 50

Percent Occurrence 10 40 0 30 Walleye Gm/Gm squid Pacific sand Salmon Gb/Bm squid

Percent Occurrence 20 pollock lance 10 0 1987 1989 1991 1993 1995 1997 1999

St. George Island (n=1203) St. George Island Walleye pollock Gm/Gm squid 70 Northern smoothtongue Salmon 60 90 Gb/Bm squid 50 80 40 70 30 60 20 50

Percent Occurrence 10 40 0 30 Walleye Gm/Gm squid Northern Salmon Gb/Bm squid 20

pollock smoothtongue Percent Occurrence 10 0 1987 1989 1991 1993 1995 1997 1999 Bogoslof and San Miguel Islands Top 5 prey or > 10% PO

Bogoslof Island (n=148) 90 80 70 60 50 (1997-2000) 40 30 20 Percent Occurrence 10 0 Northern Gb/Bm squid Gonatus tinro Walleye Northern smoothtongue pollock lampfish

San Miguel Island San Miguel Island, CA (n=518) Pacific hake Market squid Clubhook squid California lanternfish 30 70 Northern anchovy Juvenile rockfish

60 20 50

40 10 30

Percent Occurrence 20 0 Pacific hake Market Clubhook California Northern Juvenile Percent Occurrence 10 squid squid lanternfish anchovy rockfish 0 1980 1982 1984 1986 Foraging areas and diet Pribilof Islands

Vostochni 119 trips made by 97 Morjovi females, 1995-96

Polovina Cliffs Polovina

Zapadni Lukanin Little Zapadni Zapadni Kitovi Reef Tolstoi East Cliffs Gorbatch East Reef Ardiguen Reef North Staraya Artil

Zapadni

South Rookery complexes based on diet (1987-2000)

Vostochni Morjovi

Polovina Cliffs Polovina

Zapadni Lukanin Little Zapadni Zapadni Reef Kitovi Tolstoi East Cliffs Gorbatch East Reef Ardiguen Reef North Staraya Artil

Zapadni

South Pribilof Islands spewing-scat comparison Species composition

80 80 St. Paul Island St. George Island 70 70 Scats (n=2,317) Scats (n=1,127) 60 60 Spews (n=63) Spews (n=204) 50 50 40 40 30 30 20 20 Percent occurrence Percent Percent occurrence Percent 10 10 0 0

e e k m m u n ck m m u g n e c B g o B G g in o c o / /G n rring m nce llo / / n rr m n ll b m e a o b m o e l a o G to G t a L P G th H d L P G th H s d n o c ic n e oo a ye o fi if a y cific cific sal le ci c le m a a l m a a S l S ic S a S c a P P if P P ifi rn c W rn c W e a e a P h rth t P o or N N Pribilof Islands spewing-scat comparison Walleye pollock age class distribution

St. George Scats (n=1,484 otoliths in 173 samples) 80 Spews (n=105 otoliths in 27 samples) 70

40 FO

0 012345 Age Class

St. Paul Scats (n=17,827 otoliths in 902 samples) 80 Spews (n=154 otoliths in 23 samples) 70

40 FO

0 012345 Age Class 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 Breeding Islands • 1960-1974 • 1987-2000 • Stomachs (n=1,816) • Scats (n=4,178) • Top prey: • Top prey: Gonatid squid Walleye pollock Capelin Gonatid squid Walleye pollock Salmon Greenland turbot Sand Lance Bathylagidae 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 the 1977 and 1989 regime shifts

Japanese Collections Lantern fish Japanese firefly squid Mackerels and tunas Japanes sardine 90 80 70 60 50 40 30 20 Percent Occurrence 10 0 1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 2.5 PDO Index

1.5

0.5

-0.5 1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 PDO Index PDO

-1.5

-2.5 Signals of environmental change in northern fur seal diet • Effects of regime shifts not conclusive with limited data

•El Niño 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 BabaBaba Fisheries Research Agency, Japan •• ShirohShiroh YonezakiYonezaki National Research Institute of Far Seas Fisheries, Japan •• JimJim ThomasonThomason National Marine Mammal Laboratory, USA