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Zalophus californianus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CARNIVORA OTARIIDAE

Scientific Name: Zalophus californianus
Species Authority: (Lesson, 1828)
Common Name(s):
English Californian Sea Lion
Synonym(s):
Zalophus californianus subspecies californianus (Lesson, 1828)
Taxonomic Notes: This species has been considered a subspecies of Z. californianus, (Z. c. californianus), by many authors. Rice (1998), followed here, argued for the retention of Z. californianus, Z. japonicus, and Z. wollebaeki as distinct species.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Aurioles, D. & Trillmich, F. (IUCN SSC Pinniped Specialist Group)
Reviewer(s): Kovacs, K. & Lowry, L. (Pinniped Red List Authority)
Justification:
Due to its large and increasing population size, the California Sea Lion should remain classified as Least Concern.

IUCN Evaluation of the California Sea Lions, Zalophus californianus
Prepared by Pinniped Specialist Group


A. Population reduction Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.

Exploitation during the 19th and 20th centuries caused population reductions. The distribution range has not changed since the exploitation era but population numbers have increased mainly in California where the population estimate is around 238,000. The population in Mexico occupies both side of the Baja California Peninsula: the west coast has an estimated population of 75,000 – 87,000, whereas the Gulf of California population is near 30,000. The total population of California sea lions is therefore around 355,000 individuals. The population in California is reaching carrying capacity. Some colonies in the Central Gulf of California have declined by approximately 35% in the last 15 years.

A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.

California Sea Lions are abundant; they are likely reaching carrying capacity in California.

A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under A1l.

A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.

No population reduction is inferred in the near future in California or in west coast Baja California. However, some rookeries in the Gulf of California are declining and are likely to continue to decline in the near future.

B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1. Extent of occurrence (EOO): CR < 100 km²; EN < 5,000 km²; VU < 20,000 km²

Considering recent, frequent sightings of California Sea Lion in the Gulf of Alaska and the end of the Gulf of California as the northern and southern limits of its occurrence (around 6800 km) and a typical coastal distribution of 50 km, the EOO of California Sea Lions is around 340,000 km².

B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²

The AOO for the California Sea Lion, determined for the locations in which they breed (around 2,845 km) and 50 km offshore is about 142,250 km².

AND at least 2 of the following:
(a) Severely fragmented, OR number of locations: CR + 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.

The California Sea Lion has 13 rookeries from the Channel Islands to the south of Baja California and 13 rookeries inside the Gulf of California. The populations in California and Baja California show population declines during severe El Niño event, but they tend to recover to previous levels within 4-5 years. The Gulf of California does not show such fluctuations; it is genetically isolated from the remaining geographic distribution.

C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000

AND either C1 or C2:
C1. An estimated continuing decline of at least: CR + 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)
C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
or
(a ii) % individuals in one subpopulation: CR = 90–100%; EN = 95–100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.

D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5

E. Quantitative Analysis
Indicating the probability of extinction in the wild to be: Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years

Some quantitative analysis for the probability of extinction is available for rookeries of California sea lions in the Gulf of California, indicating that at least one of the 4 clusters of rookeries shows a risk for being CR > 50% in 15 years.

Listing recommendationThe California Sea Lion population is abundant and probably reaching carrying capacity in most of its wide geographic distribution. A category of Least Concern should be assigned for the global status. However, the Gulf of California Sea Lion population is genetically isolated, relatively small and some colonies have shown recent declines. Some of the local stocks in the Gulf of California should be considered Near Threatened.

Geographic Range [top]

Range Description: The California Sea Lion occurs in the eastern North Pacific from Islas Tres Marias north of Puerto Vallarta, north throughout the Gulf of California and around the end of the Baja California Peninsula north to the Gulf of Alaska. Sightings of vagrants have been reported from the southern Bering Sea in the north (Maniscalco et al., 2004) to Chiapas Mexico in the south. Females, which were only very rarely found north of Point Conception in the early 1980s, are now routinely found in northern California, where former breeding sites have been reoccupied.

Large numbers of adult and subadult males and juveniles undertake a post-breeding season migration north from the major rookeries in southern California and Baja California and winter from central California to Washington State. Smaller numbers of animals migrate to British Columbia and southeast Alaska, making it to the northern Gulf of Alaska, Alaska Peninsula, and eastern Aleutian Islands. Other animals appear to remain in the Gulf of California year round and do not undertake long migrations.
Countries:
Native:
Canada; Mexico; United States
FAO Marine Fishing Areas:
Native:
Pacific – eastern central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The California Sea Lion is abundant and increasing in some parts of its distribution. The total global population (US and Mexico) is probably around 355,000 individuals. Some colonies in the Gulf of California have decreased in the last two decades.

Exploitation during the 19th and 20th centuries caused population reductions. The distribution range has changed little since exploitation era but population numbers have increased mainly in California, where the estimate is around 238,000 individuals (Carretta et al. 2007). The population in Mexico occupies both side of the Baja California Peninsula: the west coast has an estimated population of 75,000 – 87,000 (Lowry and Maravilla 2005), whereas the Gulf of California populations is near 30,000 (Szteren et al. 2006). Total population of California sea lions is therefore around 355,000 individuals.

The California Sea Lion population is apparently reaching carrying capacity in the USA (Carretta et al. 2007) whereas in the Gulf of California the population has decreased by ~20% in the last 15 years (Szteren et al. 2006). The California Sea Lion has 13 rookeries from the Channel Islands to the south of Baja California and 13 rookeries inside the Gulf of California. The population in California and Baja California show declines during severe El Niño events that usually return to previous levels within 4-5 years. The Gulf of California does not show this sort of marked fluctuations but it is genetically isolated from the remaining geographic distribution (Maldonado et al. 1985; Schramm 2003, Bowen et al. 2005).
Population Trend: Increasing

Habitat and Ecology [top]

Habitat and Ecology: The California Sea Lion is the well-known “performing seal” of zoos, circuses and marine theme parks. It is a sexually dimorphic species, with males reaching three to four times the weight of adult females and 1.2 times their length. Pups are born with a thick brownish-black lanugo that is generally moulted by the end of the first month. The succeeding light brown juvenile coat is shed 4-5 months later and is replaced by adult coloration. Male California Sea Lions reach lengths of 2.4 m, and weights of more than 390 kg. Females only reach 2 m, and weigh an average of 110 kg. Newborn pups are about 80 cm long and weigh 6-9 kg (Peterson and Bartholomew 1967).

Age of maturity for both sexes is about 4-5 years. Females produce one pup each year after a gestation of about 11 months. A long term mark-resighting study (1980-2006) recorded a maximum observed longevity of 19 years for males and 25 years for females (Hernandez-Camacho et al. in press). Age-specific birth rates vary among age classes; 5 yr-old females show 0.59, females between 6 and 15 year-old exhibit 0.79 (Melin 2002; Hernandez-Camacho et al. in press), and between 16-25 year-old show decreased birth rate between 0.35 and 0.11 (Hernandez-Camacho et al. in press).

Pupping and breeding take place from May through July. Pupping starts earlier in the Gulf of California (May 8) than in California (May 20) and the duration of the breeding season is longer in the Gulf (13 weeks) than in California (9.5 weeks) (Garcia-Aguilar and Aurioles-Gamboa 2003). Males are highly polygynous and hold territories both on land and in shallow water near shore for periods up to 45 days. Females stay ashore with their newborn pups for about seven days before they depart for the first of many foraging trips that usually last 2-3 days and are followed by attendance with the pup at the rookery for 1-2 days. Most pups are weaned at 12 months of age. However, some pups continue to receive maternal care as yearlings and 2-3year olds (Newsome et al. 2006).

The diving pattern of lactating adult females is consistent with that of a number of other otariid species. The deepest dive recorded was to approximately 274 m and the longest dive lasted just under ten minutes. Typical feeding dives are shallower than 80 m, and last less than three minutes (Feldkamp et al. 1989; Antonelis et al. 1990). Lactating adult females are active for most of the time they are at sea and feeding bouts occur during the day and at night, with peaks of activity at dawn and dusk. The fact that feeding dives occur in bouts suggests that California sea lions are frequently exploiting patches of prey (Weise and Costa 2007).

California Sea Lions are generally found in waters over continental shelf and slope zones; however, they occupy several islands far offshore in deep oceanic areas, such as Guadalupe Island. They frequent coastal areas including bays, harbours, and river mouths.

California Sea Lions feed on a wide variety of prey, but usually maintain a preference for 4-5 species at each location, often taking what is abundant locally or seasonally in the areas they occupy (Lowry et al. 1990; Garcia-Rodriguez and Aurioles-Gamboa 2004). A lower diversity of prey is taken outside the breeding season, when many animals disperse over large areas, as opposed to during the breeding season, when preferred prey can be reduced by intense foraging activity in small areas within travelling range of the rookeries (Lowry 1991). Principle prey taken by California Sea Lions in the Pacific includes: Pacific whiting, market squid, red octopus, jack and Pacific mackerel, blacksmith, juveniles of various species of rockfish, herring, northern anchovy, and salmon (Antonelis et al. 1984; Lowry et al. 1990; Lowry 1991). Sea lions in the Gulf of California have northern anchovy, Pacific whiting, and rockfish as prey in common with animals in the Pacific and also take various species of midshipmen, myctophids and bass, as well as sardines, largehead hairtail and Eastern Pacific flagfin (Aurioles-Gamboa et al. 1984; Garcia-Rodriguez and Aurioles-Gamboa 2004). Because of their boldness and taste for commercially-important fish species, such as salmon and rockfish that are easily taken from fishing lines (DeMaster et al., 1985) California sea lions are considered a nuisance by many sport and commercial fishermen. They will also ascend rivers following spawning runs of anadromous fish and take advantage of man-made structures such as canal locks and fish ladders that concentrate prey.

Predators of California Sea Lions include Killer Whales, sharks, Coyotes and feral dogs, and until they were recently extirpated from the California Channel Islands, bald eagles were known to take young pups.
Systems: Terrestrial; Marine

Threats [top]

Major Threat(s): California Sea Lions are abundant, widely distributed and experiencing population increase through most of their range. They were historically important to native people living in coastal areas and on islands used by sea lions for rookeries. Huge middens in southern California and on the Channel Islands, with large numbers of California Sea Lion and other pinniped bones, attest to the past importance of marine mammals in subsistence cultures prior to the changes that followed the arrival of Europeans on the west coast of North America (Porcasi and Fujita 2000). In the 19th and early 20th centuries, California Sea Lions were harvested intensively for a variety of products, and hunted for bounties to reduce their impact on fisheries (Cass 1985).

California Sea Lion mortality occurs in conflicts with fisheries, by poaching, and through entanglement in marine debris (Stewart and Yochem 1987; Aurioles-Gamboa et al. 2003). Prey availability is greatly reduced during El Niño events and large numbers of pups born during these periods die of starvation, as do weaker animals from all age classes (Francis and Heath 1991). The sea lion rookeries inside the Gulf of California do not appear to be greatly effected by El Niño events (Aurioles and Le Boeuf 1991; Wielgus et al. in press).

California Sea Lions accumulate pollutants through the food chain, and large amounts of DDT, and PCBs discharged in the past, continue to accumulate in coastal marine food chains that include this species. Additionally, large amounts of agricultural and urban runoff and waste continue to be discharged into coastal marine habitats annually from numerous sources; this may have effects on sea lion immune systems and overall health. California Sea Lions do sometimes die of paralytic shellfish poisoning caused by domoic acid, a biotoxin produced by diatom blooms that enter the food web through planktivorous fish such as herring and sardine (Silvagni et al. 2005). California Sea Lions experience mortality from a number of diseases, including some such as leptospirosis contracted from terrestrial animals. They are at risk of exposure to additional diseases from contact with feral and domestic dogs and other terrestrial animals.

Conservation Actions [top]

Conservation Actions: Protection that began in the mid-20th century in the United States was solidified with the passage of the Marine Mammal Protection Act of 1972 in the United States and similar laws in Mexico. These protective measures provided the impetus for recovery of the population. Tourism at coastal sites and most offshore islands is highly regulated and controlled.

Citation: Aurioles, D. & Trillmich, F. (IUCN SSC Pinniped Specialist Group) 2008. Zalophus californianus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 19 September 2014.
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