This database contains counts of Steller sea lion pups on rookeries in Alaska made between 1961 and 2019. Pup counts are conducted in June-July. Pups are counted from the ground (by walking along the rookery), from cliff-side overlooks, and from aerial images (vertical orientation). Pup counts conducted in late June-mid July are considered to represent a complete census of pups produced at each site during the year.

This dataset contains information regarding the capture and tagging of northern fur seals on the Pribilof Islands and Bogoslof Island, Alaska, from 1992 to 2017.

This data set is comprised of satellite-linked telemetry data collected to investigate winter migration patterns and foraging strategies of adult male northern fur seals as published by Sterling et al. (2014). Satellite-linked and data-logging instruments were deployed on five adult males from St. Paul Island (Bering Sea, Alaska, USA) in October 2009. Information for the raw telemetry data used in this analysis can be found at InPort Catalog Item ID 27455 (Alaska Steller Sea Lion and Northern Fur Seal Argos Telemetry Data Archive).

The Marine Mammal Laboratories' California Current Ecosystem Program (AFSC/NOAA) in collaboration with Point Blue Conservation Science initiated long-term studies to determine pup abundance of the California Stock of northern fur seals. The California Stock is comprised of northern fur seals inhabiting San Miguel Island (and Castle Rock, and islet ~1 km northwest) and the Farallon Islands (specifically, Southeast Island) off California. Pup production is the sum of the numbers of live pups and dead pups for a given pupping season. This in turn is used as index to estimate total population abundance. Population abundance is vital to knowing the status of a particular stock or the entire species, as well as knowing what factors are driving population trends. Metadata and datasets corresponding to these studies are reported in Stock Assessment Reports (SAR) for the U.S. Congress and other stakeholders.

These data sets were used by Zeppelin et al. (2015) to model northern fur seal foraging habitats based on stable isotope values measured in plasma and red blood cells, and satellite-linked tag measures of locations and diving behavior. Foraging habitat models were developed using blood isotope samples collected from 35 adult female fur seals on three breeding colonies in Alaska during July-October 2006. Satellite location and dive data were used to define habitat use in terms of the proportion of time spent or dives made in different oceanographic/bathymetric domains. Stable isotope samples, dive data, and GPS location data collected from 15 females during August-October 2008 validated model use across years.

Adult male and female northern fur seals (Callorhinus ursinus) are sexually segregated in different regions of the North Pacific Ocean and Bering Sea during their winter migration. Explanations for this involve interplay between physiology, predator-prey dynamics, and ecosystem characteristics, however possible mechanisms lack empirical support. To investigate factors influencing the winter ecology of both sexes, we deployed five satellite-linked conductivity, temperature, and depth data loggers on adult males, and six satellite-linked depth data loggers and four satellite transmitters on adult females from St. Paul Island (Bering Sea, Alaska, USA) in October 2009. Males and females migrated to different regions of the North Pacific Ocean: males wintered in the Bering Sea and northern North Pacific Ocean, while females migrated to the Gulf of Alaska and California Current. Horizontal and vertical movement behaviors of both sexes were influenced by wind speed, season, light (sun and moon), and the ecosystem they occupied, although the expression of the behaviors differed between sexes. Male dive depths were aligned with the depth of the mixed layer during daylight periods and we suspect this was the case for females upon their arrival to the California Current. We suggest that females, because of their smaller size and physiological limitations, must avoid severe winters typical of the northern North Pacific Ocean and Bering Sea and migrate long distances to areas of more benign environmental conditions and where prey is shallower and more accessible. In contrast, males can better tolerate often extreme winter ocean conditions and exploit prey at depth because of their greater size and physiological capabilities. We believe these contrasting winter behaviors 1) are a consequence of evolutionary selection for large size in males, important to the acquisition and defense of territories against rivals during the breeding season, and 2) ease environmental/physiological constraints imposed on smaller females.

This database contains counts of adult and juvenile (non-pup) Steller sea lions on rookeries and haulouts in Alaska made between 1904 and 2019. Non-pup counts have been conducted throughout the year. Breeding season (June-mid July) non-pup counts are used for population trend analysis, while counts at other times are used for analyses of distribution and for other purposes. Non-pups are counted from the ground (by walking along the rookery), from cliff-side overlooks, and from aerial imagery (oblique and vertical orientation). Non-pup counts represent only a fraction of the total number of animals that may use a site. Sea lions haul-out less frequently in winter than in summer; thus, winter counts represent a smaller fraction of the total population than summer counts.

These data were used by Kuhn et al. (2015) to investigate how conclusions about predator-prey relationships change with increasing temporal disparity between predator tracking periods and prey surveys. Northern fur seals (n = 20) from St. Paul Island (Alaska, USA) were equipped with satellite tracking transmitters and time-depth recorders from July to October 2006. Fur seal dive and movement metrics were examined in relation to the relative abundance of the fur seals’ primary prey, walleye pollock (Gadus chalcogrammus), reported from the annual eastern Bering Sea groundfish survey. Relationships between foraging behavior metrics and prey abundance were examined within the Bering shelf survey grid cells at three time scales: within 2 weeks of the prey survey, within 1 month, and over the northern fur seal reproductive season (>4 months).

The National Marine Mammal Laboratories' California Current Ecosystem Program (AFSC/NOAA) initiated a long-term marking program of northern fur seals (Callorhinus ursinus) at San Miguel Island, California in 1975. A sample of up to 300 pups has been tagged in the foreflippers with various types and colors of tags each year between 1975 and the present. Resighting surveys for marked animals are conducted annually at summer breeding sites. Resightings are also obtained from the public when animals are observed on beaches or in fisheries. The data are used in mark-recapture models to estimate the age and sex specific vital parameters of the population and to describe age and sex specific reproductive behavior and seasonal movements of animals throughout their lives.

This dataset provides counts of harbor seals from aerial surveys over Iliamna Lake, Alaska, USA. The data have been collated from three previously published sources (Mathisen and Kline 1992; Small 2001; ABR Inc. Environmental Research and Services 2011) and newly available data from the NOAA Alaska Fisheries Science Center and the Newhalen Tribal Council. The survey years range between 1984 and 2013. Counts are reported as summed totals across all identified waypoints in the lake for each survey date. The NOAA National Marine Mammal Laboratory (NMML) (Alaska Fisheries Science Center, Seattle, Washington, USA) conducted aerial surveys of Iliamna Lake between 2008 and 2013. Surveys were conducted as part of annual harbor seal survey effort and in collaboration with local community participants and researchers at the University of Alaska. Surveys were flown using high wing, twin engine aircraft (Aero Commander 680, 690 or a de Havilland Twin Otter). Survey altitude was generally 330 m and at an aircraft speed of 120 kts. Surveys were performed seasonally for most years between 2008 and 2013. Surveys were timed so that one survey was conducted while the lake was mostly frozen (Late March/early April), one during pupping (mid July), and often several during the August molt, when the greatest number of seals typically haul out on shore. Surveys were flown, weather allowing, in the mid- to late-afternoon, when the number of seals hauled out was expected to be highest. Aircraft flight track was recorded by GPS and all seals sighted were digitally photographed using a high resolution digital SLR camera with a telephoto zoom lens (up to 400mm). Time, date, latitude, longitude, and altitude were automatically saved into the image metadata or georeferenced post survey using the GPS track and software. The total number of seals hauled out were counted from the digital photographs and recorded for each identified site. Pups were determined by their smaller size, and close proximity (less than 1 body length; either nursing or laying right next) to a larger seal. Pups were no longer recorded beyond about mid-August when many have been weaned and cannot reliably be distinguished from other non-adult seals. In 2009, a collaborative effort between NMML and researchers from the Newhalen Tribal Council (Newhalen Tribal Council 2009) provided 10 additional surveys and similar techniques were used. The raw survey count data from these surveys was provided to NMML. Aerial surveys were authorized under a Marine Mammal Protection Act General Authorization (LOC No. 14590) issued to the NMML. Between 2005 and 2007, ABR, Inc. Environmental Research and Services conducted a series of aerial surveys for harbor seals in Iliamna Lake (ABR Inc. Environmental Research and Services 2011). In addition, earlier counts from surveys conducted by ADFG (Small 2001) and a 1991 census by Mathisen and Kline (Mathisen and Kline 1992) were incorporated into the dataset to expand the historical reach. Geographic coordinates were provided (or, when not provided, determined based on descriptions or phyiscal maps) for each survey site and these sites were compared and merged with locations identified by NMML. In some cases, sites in very close geographic proximity were combined into a single site.