Bathymetric Distribution of Sea Stars (Asteroidea) off the Northern Oregon Coast

Abstract

During U.S. Bureau of Commercial Fisheries' Atomic Energy Commission trawling investigations in waters adjacent to the mouth of the Columbia River, a total of 54 species and one subspecies of sea stars was collected from bottom depths of 50–1050 fath. The sea stars in the area of study can be divided into four faunal assemblages by benthic zones: (1) an outer sublittoral fauna (50–108 fath) consisting of several shallow-water species, some of which have their apparent maximum depth of occurrence in this zone. The number of species and the availability of sea stars per hour of trawling is much lower in this zone compared to the other benthic zones in the study area; (2) an upper bathyal fauna (122–258 fath) consisting of several species having either a continuous or discontinuous circumboreal distribution; (3) a lower bathyal fauna (275–500 fath) characterized by a large number of species and a high availability of sea stars in terms of numbers and weight per hour of trawling. Several of the more frequently occurring and abundant species in this zone belong to genera endemic to the northeastern Pacific; and (4) an abyssal fauna (900–1050 fath) consisting almost entirely of species belonging to cosmopolitan genera.The bathyal-abyssal zone (585–850 fath) is considered a zone of transition because of the intrusion into this zone of elements of the sea star fauna from both the lower bathyal and the abyssal.