Relationships between size-specific sediment preferences and burial capabilities in juveniles of two Alaska flatfishes

Laboratory experiments with juvenile Pacific halibut ( Hippoglossus stenolepis Schmidt) (31–150 mm TL) and northern rock sole ( Lepidopsetta polyxystra Orr and Matarese) (15–150 mm TL) were conducted to examine relationships between sediment preference, burial performance, and general morphological characteristics. Both species demonstrated significant size-dependent changes in sediment choices during the first year of life. Highest sediment selectivity occurred in the smallest individuals of both species. There was a strong positive relationship between sediment choice and ability to bury quickly and completely, although the choices made by rock sole were less specific than those of comparably sized halibut and were less closely concordant with burial capability. In both species, fish >80 mm TL were relatively nonselective, except that they avoided sediments with the largest grain size (i.e., granules and pebbles). Pacific halibut have narrower, more powerful bodies than rock sole and were stronger burrowers than rock sole. Rock sole were more cryptic than halibut in general locomotion and color-matching capability, and appear to depend to a lesser extent on burial for survival than do halibut. Association with sediment is the first line of defense for juvenile flatfishes, and the relationships shift rapidly with fish size during the first year of benthic life. Therefore, habitat descriptions and models for young post-settlement flatfishes need to be made for narrow size classes.