STOCK STRUCTURE AND MOVEMENT OF TAGGED SABLEFISH, ANOPLOPOMA-FIMBRIA,IN OFFSHORE NORTHEAST PACIFIC WATERS AND THE EFFECTS OF EL-NINO SOUTHERN OSCILLATION ON MIGRATION AND GROWTH

Sablefish in the northeast Pacific are found in commercial quantities from the Baring Sea, the Aleutian Islands, throughout the Gulf of Alas ka, and south along the west coast of Canada and the U.S. to Baja Cali fornia. Tag-recovery data support a two-population hypothesis througho ut the North American range: an Alaska population ranging from the Ber ing Sea, including the Aleutian Islands and extending down through the Gulf of Alaska to northwest Vancouver Island, Canada; and a west coas t population extending from southwest Vancouver Island to Baja Califor nia. Tag recoveries indicate that these two populations mix off southw est Vancouver Island and northwest Washington, and to a lesser extent off southern Washington and Oregon. Alaska sablefish, which commonly m igrate over 500 n mi, are more mobile than west coast sablefish. Tag r ecoveries for sablefish tagged in Alaska have shown strong mutual exch anges between nearly all areas. In contrast, west coast sablefish have shown far less migratory behavior. Tagging data with respect to bathy metry are difficult to interpret in both regions owing to the fact tha t tagging and recovery effort do not cover the full bathymetric range of adults. Results of analysis of tag-recapture growth data were consi stent with patterns observed for several other pelagic and demersal sp ecies. That is, El Nino-Southern Ocean Oscillation events appeared to retard the growth of sablefish along the west coast and to enhance gro wth of Alaska sablefish. The timing of recoveries from sablefish tagge d off Alaska and recovered off southwest Vancouver Island and Washingt on-Oregon suggests that movement south correlates positively with stro ng upwelling in this southern area. Although sablefish trap-index surv eys show a north to south cline in the percentage of large sablefish ( >60 cm, and possibly of Alaska origin) sampled in length frequencies a long the west coast, we were unable to correlate annual fluctuations i n these percentages with upwelling strength.