Sablefish Populations on Gulf of Alaska Seamounts
November 15, 2017
The Gulf of Alaska seamounts are a group of undersea mountains of volcanic origin rising from the ocean floor at depths of 3,200–4,000 m to within 400–800 m of the surface.
NOAA Fisheries first conducted exploratory fishing on nine Gulf of Alaska (GOA) seamounts in June and July 1979 (Hughes, 1981).
Summary of Methods and Results
Using trawls and traps, they found that sablefish were the dominant finfish on each of the seamounts and that trap catch rates of sablefish were higher than those from survey sites off southeastern Alaska. There were more than twice as many males as females, and nearly all sablefish were ripe, spawning, or recently spent. However, only older and larger fish were caught on the seamounts, suggesting that the seamount populations are maintained by the migration of mature fish from the continental slope rather than by local recruitment.
Summary of Findings
Tagged sablefish released in the Bering Sea, Aleutian Islands region, and the western and central GOA have been recovered on GOA seamounts, verifying the occurrence of slope to seamount migration. Of 99 tagged sablefish released on 5 GOA seamounts in 1979, 5 have been recovered on the seamount where they were tagged, and none have been recovered elsewhere.
NOAA Fisheries revisited seven of the sea-mounts sampled in 1979 and one (Murray Seamount) that was not sampled in 1979. Sablefish were tagged and released on the seamounts during 1999–2002 to determine the extent, if any, of emigration from the seamounts back to the continental slope and movement between seamounts. A second objective was to gather biological information from the seamount sablefish populations.