Migration patterns of Pacific halibut Hippoglossus stenolepis in the southeast Bering Sea

Currently, it is assumed that eastern Pacific halibut Hippoglossus stenolepis belong to a single, fully mixed population extending from California through the Bering Sea, in which adult fish disperse randomly throughout their range during their lifetime. However, we hypothesize that Pacific halibut dispersal and behavior are more complex than currently assumed and are not spatially or temporally random. To test this hypothesis, we studied seasonal dispersal and behavior of Pacific halibut in the Bering Sea and Aleutian Islands. Pop-up Archival Transmitting tags provided no evidence that Pacific halibut moved out of the Bering Sea and Aleutian Islands region into the Gulf of Alaska during the mid-winter spawning season, supporting the concept that this region may contain a separate spawning component of adult fish. There was evidence for geographically localized groups of Pacific halibut along the Aleutian Island chain, as all of the fish tagged there displayed residency, with their movements possibly impeded by deep passes between islands. Mid-winter aggregation areas of Pacific halibut are assumed to be spawning grounds, of which two were previously unidentified and extend its presumed spawning range ~1000 km west and ~600 km north of the nearest documented spawning area. The summarize