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We conducted a mark-recapture study of California sea lions (Zalophus californianus) using pups branded on San Miguel Island, California, from 1987 to 2014, and annual resightings from 1990 to 2015. We used the Burnham model (Burnham 1993), an extension of the Cormack-Jolly-Seber mark-recapture model, which includes recoveries of dead animals, to analyze age, sex, and annual patterns in survival. Generally, females had higher survival than males. For female pups, the average annual survival was 0.600 and for male pups it was 0.574. Yearling survival was 0.758 and 0.757 for females and males, respectively. Peak annual survival was at age 5 and was 0.952 for females and 0.931 for males. Pups with larger mass at branding had higher survival as pups and yearlings, but the effect was relative within each cohort because of large between-cohort variability in survival. Annual variability in sea surface temperature (SST) affected survival. For each 1°C increase in SST, the odds of survival decreased by nearly 50% for pups and yearlings; negative SST anomalies yielded higher survival. Annual variation in male survival was partly explained by leptospirosis outbreaks. Our study provides a unique view of one demographic parameter that contributed to the successful recovery of the California sea lion population.

We used stable carbon ( 13 C) and nitrogen ( 15 N) isotopes to examine ontogenetic dietary changes in 289 California sea lions (Zalophus californianus )a t San Miguel Island, California during 2004–2007. Tissues analyzed included fur, red

∗National Museum of Natural History, Smithsonian Institution, Washington, DC †Alaska Fisheries Science Center, NOAA ‡University of Oregon, Eugene, Oregon ∗∗Humboldt State University, Arcata, California ††California Polytechnic State University, San Luis Obispo, California ‡‡University of Oregon, Eugene, Oregon §University of California, Los Angeles, California ¶University of California, Santa Barbra, California

Aerial surveys of harbor seals on land produce only a minimum assessment of the population; a correction factor to account for the missing animals is necessary to estimate total abundance. In 1991 and 1992, VHF radio tags were deployed on harbor seals (n = 124) at six sites in Washington and Oregon. During aerial surveys a correction factor to account for seals in the water was determined from the proportion of radio-tagged seals on shore during the pupping season. This proportion ranged from 0.54 to 0.74. Among the six sites there was no significant difference in the proportion of animals on shore nor was there a difference in age/sex categories of seals on shore between sites. The pooled correction factor for determining total population abundance was 1.53. An additional 32 seals were radio tagged in 1993 at one of the sites used in 1991. Comparing data from the two years, we found no interannual variation. Aerial surveys of all known harbor seal haul-out sites in Washington (n = 319) and Oregon (n = 68) were flown during the peak of the pupping season, 1991-1993. The Washington and Oregon harbor seal population was divided into two stocks based on pupping phenology, morphometics, and genetics. Mean counts for the Washington inland stock were 8,710 in 1991, 9,018 in 1992, and 10,092 in 1993. Oregon and Washington coastal stock mean counts were 18,363 in 1991, 18,556 in 1992, and 17,762 in 1993. Multiplying the annual count by the correction factor yielded estimates of harbor seal abundance in the Washington inland stock of 13,326 (95% CI = 11,637-15,259) for 1991, 13,798 (95% CI = 11,980-15,890) for 1992, and 15,440 (95% CI = 13,382-17,814) for 1993. In the Oregon and Washington coastal stock the corrected estimate of harbor seal abundance was 28,094 (95% CI = 24,697-31,960) in 1991, 28,391 (95% Cl = 24,847-32,440) for 1992, and 27,175 (95% CI = 23,879-30,926) for 1993.

The attendance patterns of California sea lions were studied during the non-breeding seasons from 1991 to 1994. Lactating females frequented the rookery to nurse their pups until weaning; most non-lactating females left the rookery for the season. Females spent over 70% of their time at sea except in 1993 when they spent 59% of their time at sea. The mean foraging trip length in the winter and spring ranged from 3.3 to 4.6 d; the mean nursing visit ranged from 1.2 2 to 1.4 d. The duration of foraging trips and nursing visits was variable over the season for individuals but no pattern of change was detected. Interannual and seasonal differences were not significant for time at sea, visits ashore, or foraging-trip duration before, during, or after the 1992-1993 El Nino event. Pups spent an average of 66.6% of their time ashore and up to three days away from the rookery during their mother's absence. Most females and pups stayed associated until April or May. The results suggest that seasonal movement of prey is more important in determining attendance patterns late in the lactation period than increasing energy demands of the pup.

Genetic substructure among groups of Pacific harbor seals, Phoca vitulina richardsi, along the western coast of the United States was investigated using mitochondrial DNA sequences. Blood and tissue samples were removed from 86 seals inhabiting Puget Sound and the Pacific coasts of Washington, Oregon, and California. A 320 base-pair segment of the control region was amplified using the polymerase chain reaction and directly sequenced. These data indicated a high level of diversity. Thirty variable sites were found that define 47 mitochondrial haplotypes. Among groups of P. v. richardsi sampled, 5 haplotypes were shared, but most (42) were unique to a locality. Haplotypic frequency and an Analysis of Molecular Variance (Amova) revealed significant differences (P= 0.001) among regions. Phylogenetic analysis indicated Puget Sound seals possess unique divergent lineages not found in seals from the coasts of Washington, Oregon, and California. These lineages may represent haplotypes from north of Washington, which is consistent with late reproductive timing of harbor seals from Puget Sound.

Description d'un systeme permettant d'etudier les deplacements pelagiques de l'elephant de mer. L'appareil permet, a partir de mesures precises de la photoperiode en fonction de la latitude et de la longitude, d'enregistrer les differentes localisations au cours de la periode passee en mer. L'utilisation de cette nouvelle technique est seulement limitee par la necessite de recuperer l'appareil au moment des atterrissages

We used small microprocessor-based, time-depth recorders to document the diving patterns of six adult male northern elephant seals (Mirounga angustirostris) from San Miguel Island, California. The recorders stored measurements of hydrostatic pressure every 30 or 60 set while the seals were at sea for 107 to 145 d in spring and early summer; collectively, over 36,000 dives were recorded. Seals dove continually while at sea, most often to depths of 350–450 m although two seals had secondary modes at about 700–800 m; maximum depths for two seals of 1,333 m and 1,529 m are the deepest yet measured for air-breathing vertebrates. Seals were submerged about 86% of the time they were at sea, rarely spending more than 5 min at the surface between dives; 99% of all post-dive surface intervals were shorter than 10 min. Dives averaged 21–24 min, the longest was 77 min. The uninterrupted patterns of long dives punctuated by brief surface periods suggest that most if not all dives were well within these seals’aerobic limits. Dives of bulls were, on average, about 18% longer than those published earlier for cows, evidently because of the substantially greater body mass of bulls and allometric scaling of dive endurance. Dive depths and dive durations varied seasonally; depths were greatest in spring, durations greatest in early summer. During each season dives were deepest during the day and shallowest at night except for the sixth seal whose consistently shallow dives (50–150 m) in spring were independent of time of day. Prey remains recovered by lavage from seals’stomachs were primarily of vertically migrating, epi- and meso-pelagic squid. The die1 patterns in dive depths suggest that five seals dove to and foraged in the offshore mesopelagic zone, pursuing those vertically migrating prey. The sixth seal behaved similarly in early spring and early summer but may have foraged in nearshore epibenthic habitats in spring.

We studied the haul-out patterns and movements of harbor seals (Phoca vitulina richardsi) on San Miguel Island, California, from 23 October through 6 December 1982 by attaching a radio transmitter to each of 18 seals and monitoring their presence ashore with continuously scanning receivers. Seals hauled out at all hours although, on average, the largest proportion of tagged seals was ashore between 1300 and 1500 h. Median durations of haul-out bouts of individual seals ranged from 4.7 to 21.8 h; 81% of all haul-out bouts were less than 12 h and 3% were longer than 24 h. Eighty-one percent of the seals that were resighted at least twice used only the sites where they were tagged; two seals used two sites and one seal used three. Most seals were hauled out on fewer than 51% of the days sampled. On average, about 41% of tagged seals hauled out each day whereas an average of about 19% was hauled out during peak afternoon hours. Using telemetry data to correct a count of 412 seals made during an aerial survey, we estimated absolute abundance at about 2,168 seals; a modified Peterson mark-recapture model produced an estimate of about 1,445 seals.