Patterns of movement, growth, and survival of adult sablefish (Anoplopoma fimbria) at contrasting depths in slope waters off oregon

Abstract

Demersal fish inhabiting continental slopes experience colder temperatures, increasing hydrostatic pressure, decreasing oxygen saturation, and decreasing productivity with increased depth. We examined depth-related patterns in smalland large-scale movement, growth, and relative survival of sablefish (Anoplopoma fimbria) tagged during 1996–2004 in Oregon waters at depths of 141–1225 m; 2614 of 17,400 fish were recaptured as of December 2016. Recapture rates indicated significant size-dependent mortality. Discard mortality was affected by surface temperature for small fish (<55 cm in fork length [FL]) from upper slope depths (<400 m). Depth effects on recapture rates reflected differences in fishing effort. Most recaptures were near the initial capture depth. Although 91% of the recaptures were within 200 km of the tagging location, some individuals migrated thousands of kilometers, reaching the western Aleutian Islands. Growth rates were faster for females than for males and decreased with depth. Sablefish in the deepest depths sampled had extremely slow growth rates (<2 cm FL/year), low dispersal (2.4%), and were largely female (81%). Prior studies of age distribution indicate that deep slope habitats also support greater longevity, potentially providing a refuge for older fish and a buffering effect to longevity overfishing, depending on spatial differences in exploitation rates.