At the western end of the Aleutian Island chain, a commercial fisherman in October of 2009 hauled in a long line with a nice catch of sablefish - also known as black cod. He noticed an orange tag sticking out of the dorsal fin of one fish. He returned the tag to a fish and Game office and learned that fish was tagged by biologists two and a half years earlier and almost 2,000 miles away in Southeast Alaska.
Fish and Game biologists tag sablefish in late spring at locations along Chatham Strait in Southeast Alaska. The sablefish are caught using pots strung on a longline, and because they are not caught with hooks, the survival rate of released fish is excellent. Tagged fish mix with the general population of sablefish in the area. Comparing the release locations to the subsequent capture locations helps biologists understand sablefish movements.
Sablefish are long-lived, and can reproduce for decades once mature. Sablefish are known to live into their 90s, and Fish and Game aged a 97-year old sablefish caught in Prince William Sound. They also inhabit some incredibly deep waters, from 300 to almost 3,000 meters deep, waters about 1,000 to 9,000 feet deep.
In past years surveyors have tagged between 6,000 and 8,000 fish each year, and in 2017 almost 800 tags were returned. One sablefish was caught five years after it was tagged. Some remarkable travels have been documented: a sablefish tagged in upper Chatham Sound in May 2012 was caught four years later in April of 2016 off the coast of Eureka, California, more than 2,000 km (1,300 miles) away.