Alaska Ecosystems Program

Russian Steller Sea Lion Research Update (cont.)

- Pup Branding and Sampling:

Figure 1.  Click image to enlarge.

In the Russian Far East, the first attempts at tagging newborn Steller sea lion pups to study their winter migrations occurred during the mid-1960s. However, the sample sizes were small (45 pups), and the work did not provide any useable results. Ultimately, several more attempts were made to tag pups with metal and plastic tags, and the results of this work provided the first data on migrations of young Steller sea lions between rookeries and haulouts. However, these tags were only retained for 3-4 years.

The first mass branding of pups in Russia was performed during the joint research cruise of TINRO and NMML scientists in summer 1989, and branding has been carried out regularly since 1996 (Table 2). In total, 8,486 Steller sea lions have been marked on 9 of the 10 major Steller sea lion rookeries in Russian waters, including 1,524 sea lions that were tagged with front flipper tags and 6,962 that were branded (Fig. 1, Table 2).

In parallel with pup branding, morphometric data (body length, axillary girth, and weight) were regularly collected and, beginning in 2002, a small tissue sample was taken from each branded pup for genetic research. In addition, blood samples were collected from 10-30 animals at each site to monitor health conditions and for archival purposes.

- Observations of Branded Sea Lions:

In Russia, observations of branded Steller sea lions are carried out mainly on the breeding rookeries (Table 3). Two or three observers spend up to 3 months camped near 8 of the 10 primary rookeries to collect daily resights of branded sea lions. As with similar work in Alaska, digital photos are collected for verification of the encounter and for positive identification of individual animals (photos of brands are compared with the brand resight database).

For juvenile animals (ages 1-3), all observations note the presence or absence of a tending adult female, and for mature females the presence of an older dependent or a newborn pup is also noted. All observations also note whether the adult female is nursing and if any copulations are observed. Data are entered into a database daily.

In addition to the ground-based observations on the rookeries, vessel surveys over large areas are conducted to record and photograph branded sea lions seen on haulouts, and similar data are collected on reproductive status. Ultimately, all of this information is collated at the completion of the field season and combined into a single Steller sea lion brand resight database.

All the data received from occasional respondents—fishermen, hunters, local residents, etc.—are also entered in this database. Data on the branded sea lion encounters along the coast of Hokkaido (Japan) are regularly provided by students of Hokkaido University and biologists from the Hokkaido National Fisheries Research Institute. There are currently more than 100,000 records about encounters of 2,648 branded Steller sea lions in the database.  (continued)