AFSC/NMML/CCEP: California sea lion adult male migration locations, 1995-2000

The migration and movement patterns of male California sea lions (Zalophus californianus) were investigated to determine the timing and distance of the migration. Adult male sea lions were instrumented with satellite-linked instruments in Puget Sound, Washington, before the southbound migration between 1995 and 2000. This dataset contains the ARGOS location data from the instrumented animals that subsequently was analyzed by the California Current Ecosystem Program (AFSC/NOAA).

This dataset was analyzed in order to investigate the timing, location, and distance of the migration of the adult male California sea lions.

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Gearin, P.J., S.R. Melin, R.L. DeLong, M.E. Gosho, and S.J. Jeffries. 2017. Migration patterns of adult male California sea lions (Zalophus californianus). NOAA Technical Memorandum NMFS-AFSC-346. doi:10.7289/V5/TM-AFSC-346.

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Marine Mammal Laboratory

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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.

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Location data obtained from satellites were summarized by the Service ARGOS (Landover, Maryland, USA) (Service ARGOS 1996). A quality code was assigned to each location based upon the estimated accuracy of the location relative to the true position of the animal. Locations were classified as Z, B, A, 0, 1, 2, 3, indicating poor to good quality locations. The potential error of a location was 150 m for quality level 3 locations, 350 m for quality level 2 locations, and 1,000 m for quality level 1 locations. The potential error for quality levels 0, A, B, and Z was not estimated by Service ARGOS.

The satellite instruments were programmed to transmit location data twice daily, 0200 to 0500 hours and from 1100 to 1400 hours.

Data at capture (including morphometric information) were transcribed in datasheets/books while in the field. At the end of the day, data were entered into the database. Information in each field were cross checked with the original datasheet for errors, duplicates, and misspellings.

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.

Adult male California sea lions were captured on floating haul-out traps at Shilshole Bay near Seattle, Washington (47°40.80 N, 122° 24.66 W). After sea lions were captured, they were moved from the trap platform onto a 10 × 3 m barge where they were sorted into one of two transfer cages for handling. Sea lions were weighed, measured, and hot iron branded on the dorsal rump area with unique numbers. Sea lions also were tagged on each foreflipper with numbered plastic tags (All flex USA Inc., Dallas, TX). The combination of the brand and flipper tags made individuals readily identifiable when resighted.

Satellite instruments were deployed on nine adult male California sea lions from 1995 to 2000 between March and June before the onset of the southbound migration. Seven of the instruments were satellite-linked time depth recorders (SLTDRs) and two were SPOT tags (Wildlife Computers, Bellevue, WA) which provided only position data. The satellite instruments were set in an epoxy resin mold and glued to the dorsal pelage of each sea lion using 5-minute epoxy. A VHF radio tag was attached alongside the satellite housing unit to assist in locating animals and recovering instruments at a later date. The satellite instruments were programmed to transmit location data twice daily, 0200 to 0500 hours and from 1100 to 1400 h. The instruments also were programmed to record wet or dry status used to determine if the animal was on-land and at-sea for each position. Location data obtained from satellites were summarized by the Service ARGOS (Landover, Maryland, USA) (Service ARGOS 1996). A quality code is assigned to each location based upon the estimated accuracy of the location relative to the true position of the animal. Locations were classified as Z, B, A, 0, 1, 2, 3, indicating poor to good quality locations. The potential error of a location was 150 m for quality level 3 locations, 350 m for quality level 2 locations, and 1,000 m for quality level 1 locations. The potential error for quality levels 0, A, B, and Z was not estimated by Service ARGOS. All quality level Z locations were discarded before analysis. Each location was then inspected to determine if it should be retained for the analysis. The locations were considered on a point-to-point basis using a maximum swim speed of 3 m/s (Feldkamp et al. 1989, Ponganis et al. 1990) and the elapsed time between consecutive locations to determine whether the location was within the swimming capabilities of the animal. Locations were discarded if the distance between the two points was greater than the possible travel speed of the animal. To minimize dependence among locations, only one location was selected for each day for each sea lion. When more than one location was obtained for the same day, the location with the best quality was used in the analysis. If multiple locations on the same day had the same quality, a single location was randomly chosen. Dataset reflects spatial information of instrumented male California sea lions throughout their migrations.