The meso- and bathypelagic cephalopod fauna of the Gully submarine canyon

Abstract

Four midwater-trawl surveys were conducted during the summers of 2007–2009 and the spring of 2010 to document the meso- and bathypelagic biodiversity of the Gully canyon. These surveys collected 3871 cephalopods of at least 38 species in 22 families. The numerically dominant 13 species and one genus together comprised 90% of the total taken in standard survey sets. Each of those taxa uses the Gully in a different way, including within-family differences for the two cranchids and two mastigoteuthids. Oegopsids of note include Brachioteuthis beanii, which was the most abundant species in summer but entirely absent in March. The cirrate octopod Stauroteuthis syrtensis was collected in large numbers (n = 142) and a wide range of sizes (9–185 mm) suggesting it may complete its life cycle within the canyon. These results expand understanding of the trophic structure in the Gully and establish a baseline for future monitoring of ecosystem change.