AFSC/MML/CCEP: Pup production of the California Stock of northern fur seals from 1969 - 2023

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.

Provide estimates of pup production of the California Stock of northern furs seals. Information provided estimating population abundance for this stock and used in Stock Assessment Reports.

CCEP LAN; CIPinnipedCensusMaster Access database. Point Blue Conservation Science (Farallon Islands).

Tables include information about the annual counts (live and dead) of the California Stock of northern fur seals (San Miguel and Farallon Islands). See "Child Items" for more detailed information.

The user is responsible for the results of any application of these data for other than their intended purpose. NOAA denies liability if the data are misused. Applications or inferences derived from the data should be carefully considered for accuracy. Whereas every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

San Miguel Island, California Channel Islands; Farallon Islands; Waters off the California coast.

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The dataset is archived with the NOAA National Centers for Environmental Information (NCEI). Acknowledgement of NOAA/NMFS/AFSC, as the source from which these data were obtained in any publications and/or other representations of these data is suggested. Communication and collaboration with dataset authors is strongly encouraged prior to use.

The dataset is available for download via the NCEI Ocean Archive System at https://www.ncei.noaa.gov/archive/accession/0303532.

There are no legal restrictions on access to the data. They reside in public domain and can be freely distributed.

User must read and fully comprehend the metadata prior to use. Applications or inferences derived from the data should be carefully considered for accuracy. Acknowledgement of NOAA/NMFS/AFSC, as the source from which these data were obtained in any publications and/or other representations of these, data is suggested. Data should be cited as: Orr, A. J., P. Warzybok, and J. R. Tietz. 2025. Pup production of the California Stock of northern fur seals from 1969 - 2023. NCEI Accession 0303532. NOAA National Centers for Environmental Information. Dataset.

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Metadata are subject to revision at any time and information within the metadata record should not be cited without author consent. Whereas every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

Microsoft Access database and Microsoft Excel csv files.

Data represent a vast majority of count information for northern fur seals at San Miguel and the Farallon Islands. The minor exception is missing data that was not collected at Castle Rock off of San Miguel Island, which was not visited annually due to weather and sea-state conditions.

Ground counts - the biases associated with ground counts are two-fold. Firstly, there are some sections of the island where there are a lot of pups (>> 100). Because the animals are moving around and they are in a dynamic environment, it is difficult to count accurately. Secondly, during these situations one counter consistently has higher counts than the other resulting in over/under-estimations between counts and differences in methodologies. Surprisingly, precision in overall annual counts remains high (within 10%).

Aerial counts - The bias associated with aerial counts is not accounting for pups not seen because they are in spaces underneath boulders, bluffs, other animals. However, more accurate counts can be produced using this method because the images are static and can be recounted over and over, if necessary.

Studies have been conducted to examine the difference in counts (accessing precision) by methodology and between counters. Only counts within 10% of each other are acceptable.

Annual census data from San Miguel and the Farallon Islands are almost complete compared to the planned amount. The only exceptions are years where counts were not obtained at Castle Rock (off San Miguel Island) due to weather or sea-state conditions.

Ground counts (San Miguel Island) - two counters stand side-by-side to have a similar perspective to count pups using tally-counters. they count from bluffs or on the rookery. If the latter, a non-counter or one of the counters moves ahead to slowly spook the non-ups away from the area so that only pups remain to be counted. After counts are completed in an area, they are compared. If the counts are not within 10% of each other, pups in the area are counted again.

Contact Data Steward for specific information about inconsistencies in the data.

Data entered from field data books to electronic databases are examined twice to deal with any transcribable errors.

For counts made on mosaic images, a subset of images are counted by another person to verify counts.

Data not automatically processed

IT Security and Contingency Plan for the system establishes procedures and applies to the functions, operations, and resources necessary to recover and restore data as hosted in the Western Regional Support Center in Seattle, Washington, following a disruption.

San Miguel Island - each year, usually between the last two days in July and the first two days in August, a live-pup census is conducted at San Miguel Island and Castle Rock. Counts are conducted either on the ground in a mobile blind or on a bluff at San Miguel and by walking in safe spots on Castle Rock. Two independent counters are used. For aerial counts, a pilot with a visual observer conducts the counts in areas where animals will not be disturbed. Afterward, counts between the two counters are compared to determine if they are within 10% of each other. If not, the area is recounted. If they are, the mean of the counts are used to sum and determine the total of live pups for that year. For aerial counts, a person counts the number of pups on mosaics created from groups of images obtained from camera systems on the aircraft. A subset of images are counted by another counter to access precision. Mortality counts included hooking each pup carcass seen and dragging it to an area/pile where it could not be displaced by water (high tides, waves) so that they would not be recounted during a subsequent mortality survey. In areas where carcasses were not stacked, they were just counted around the time of the live-pup census. Decomposition state was noted and all carcasses counted. Live and dead pup counts were stored into a database.

Farallon Islands - live-pup counts are conducted in July and August from a light atop Southeast Farallon Island. When accessible (usually starting in August after seabirds have completed their breeding season), counters go to the west-end of the island to conduct other surveys (much closer than the lighthouse). When possible, an aerial (crewed, fixed-wing aircraft) census is conducted. Information from the method that produced the highest counts is used. Dead-pup counts are conducted from the lighthouse on the island. However, because not all the carcasses can be seen, and they are washed away or almost completely decomposed by the time researchers are able to properly count the number of dead individuals, the live-pup counts provide a minimal estimate of pup production on the island.