Cobb Seamount - Biology

Biology

Although it is one of over 100 underwater features in the region, Cobb Seamount is the only one known to extend well upwards into the region of the ocean penetrated by light. Like many other seamounts, Cobb Seamount is a local biological hotspot and functions as an "island of stability" for local organisms. It supports an extensive fish population, mostly Sebastes species and especially Sebastes miniatus. Bird life has been noted in the area of its summit, indicating that it is a prime fishing ground.

The summit of the volcano is dominated by a carpet of Hinnites multirugosus, which forms the base of a dense ecosystem of sponges and other small, sessile organisms. The species is otherwise scarce in its distribution in the Pacific; its abundance is accommodated by the scarcity of its chief predator, the Sea Star Orthasterias koehleri. The reason for the sea star's disparity is unknown, as it is extremely common on nearby seamounts.

The steeper flanks of the volcanoes are carpeted by coralline algae of the Lithothamnion and Lithophyllum geneses. In some areas, Borgiola pustulosa is more common. Red-colored colonies of demosponge and related species predominant the ecosystem, which includes sea urchins, sponges, algae, anemones, and gastropods. While overall the species diversity on the seamount is lower than a comparable area on the surface, the species present have grown in greater numbers and have formed larger colonies, to the point that there was little to no bare rock surface on the seamount, and none has been found in expeditionary dives. Some endemism to the seamount has also been noted.

The seamount's abundant sea life has made it a target for heavy fishing since the 1960s. However, the fishing is very difficult to monitor, since Cobb lies outside of the U.S. Exclusive Economic Zone and therefore fishing vessels are not regulated. It is known that it has been the site of trawling, gill net, and longline fishing for some time, mostly by the Japanese and Oregonian fleets. In 1993, the National Oceanic and Atmospheric Administration sponsored a study on the seamount, which concluded that concerns as to overfishing at the seamount have some merit. The study also notes that fishermen there have different fishing patterns, because of different physical conditions at the seamount.