The Life History and Status of the California Sea lionThe Life History and Status of the California Sea lion

•• Life HistoryLife History

•• Population StatusPopulation Status

•• Population RegulatorsPopulation Regulators

Sharon RSharon R. . MelinMelin NOAANOAA//National Marine Fisheries ServiceNational Marine Fisheries Service

Alaska Fisheries Science CenterAlaska Fisheries Science Center National Marine Mammal LaboratoryNational Marine Mammal Laboratory

SeattleSeattle, , WAWA

Canada

Washington

Oregon

California

Mexico

California Sea Lion Distribution

Western Baja California Stock

Gulf of California Stock

U.S. Stock

California sea lion U.S. rookery locations

45%

45%

6%

4%

Canada

Washington

Oregon

California

Mexico

California Sea Lion Life History

Year round Sardine Anchovy

Pacific hake Market squid

Mackerel

September

to May

Pacific hake eulachon Salmon squid

••PolygynousPolygynous ••Sexually dimorphicSexually dimorphic

Annual Reproductive Cycle of a California sea lion

J J A S O N D J F M A M Breeding Non-breeding

Females

Males

Pupping Breeding Gestation

Lactation Implantation Migration

From Pup to Predator • Dependent on mother for

nutrition until 6 months old • Begin swimming at 8

weeks • Begin feeding at 6-7

months • Wean at 11 months old • Pup survival is less than

50% to the first birthday • Causes of mortality are

starvation and disease

• Once weaned, first year survival is 77%

• Annual survival after age 2 increases to 95%

• Primary causes of mortality are predation, interactions with humans and diseases

From Pup to Predator

From Pup to Predator

• Reproductive at 4 or 5; all by age 7 • 77% give birth each year • Site fidelity once reproductive, little

emigration • Survival declines after 11 years • Reproduction declines after 15 years • Life span at least 24 years in the wild

From Pup to Predator • Can reproduce at 4-5 years;

most don’t • Must develop physical and

social maturity • Mean reproductive age is 13

years • Only 10% of males born

survive to reproductive age • Longevity ~19 years

More on Males

• Present at breeding colonies May-early August, then migrate north

• Mean territorial tenure 10 days (range 1 day – 2 months)

• Males breed with one to many females depending on location, tenure, and female choice

• Fidelity to territory over time

• May hold territory up to 6 consecutive years

Population Status and Trends • Historical population level unknown • Protected under MMPA in 1972 • Monitoring population since 1975

- Live pup counts at all breeding colonies since 1975 - Pup mortality surveys at San Miguel Island since1990 - Marking at San Miguel Island for estimating survival, natality

and longevity since1987 • California sea lions are not listed as “threatened” or

“endangered” under the ESA and are not listed as “depleted” or as a “strategic” stock under the MMPA

• Potential Biological Removal (PBR) is 8,511 animals

Live Pup Count 1975 – 2005

Source: NMFS Draft Stock Assessment Report 2007

How many sea lions are there?

A correction factor to estimate total population from live and dead pup counts has been developed using the life table for the northern fur seal and the growth rate of the California sea lion population. From a live pup count of 48,277 and early pup mortality of 15% in 2005

and a correction factor of 4.28, we predict a total population size of 238,000 sea lions in U.S. waters. (NMFS Draft Stock Assessment Report 2007) In 2000, the Western Baja California Stock was estimated at 74,000 (Lowry and Maravilla-Chavez 2000)

Population Regulators

• Population growth is currently regulated by pup and yearling survival

- Environmental changes (e.g. El Niño, Pacific Decadal Oscillations)

- Disease (e.g. parasites) • Juvenile (2-3 years) and adult mortality is low

- Predation - Biotoxins - Disease - Human interactions

El Niño and Disease: First Year Mortality

0.000.100.200.300.400.500.600.700.800.901.00

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

Year

Surv

ival

Rat

e

5% growth rate 1% growth rate

El Niño Hookworm

Warm Phase Cold Phase

Biotoxins and Disease

• Domoic acid - Neurotoxin produced by Pseudo-nitzschia australis, attacks the nervous system and leads to seizures and brain damage that can lead to death

- 74% of documented adult female mortalities

- Sub-lethal doses lead to reproductive failure

• 20% of stranded adult population positive for urogenital cancer leading to reproductive failure and death

Human Interactions

• ≥ 159 annual fishery related mortalities

• ≥ 74 annual non-fishery related mortalities

• Minimum 233 annual mortalities

Source: NMFS Draft Stock Assessment Report 2007

Estimated human-caused mortality between 2000 and 2004:

•• UU..SS. . population breeds in California Channel Islandspopulation breeds in California Channel Islands •• Life historyLife history: : longlong--livedlived, , slow reproducersslow reproducers •• 20052005 population estimate population estimate 238,000238,000 •• Population is at or near KPopulation is at or near K •• Population growth is mostly driven by pup and yearling Population growth is mostly driven by pup and yearling

survivalsurvival •• Other factors that may influence population growth include El Other factors that may influence population growth include El

NiNiññoo, , biotoxinsbiotoxins, , and human interactionsand human interactions •• Current human caused mortality poorly estimated but likely Current human caused mortality poorly estimated but likely

below PBR of below PBR of 8,5118,511 •• California Current in cold phase which should favor California Current in cold phase which should favor

California sea lions but positive effects are currently mitigatCalifornia sea lions but positive effects are currently mitigated ed by diseaseby disease

SummarySummary

Questions?