Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Patterns of movement in Pisaster ochraceus on a seawall in Monterey Harbour
Student Author(s): Calhoun, Katherine E.
Faculty Advisor(s): Baxter, Chuck
Pages: 23
Location: Final Papers Biology 175H
Date: June 1983
Keywords: echinoderms
Abstract: Surveys were made of the vertical distribution of Pisaster ochraceus and its possible prey items on a seawall in Monterey harbour. Both predator and prey were found to fall into the same zone, dominating the region from .25 to .6 m above mean low low water. The diet of this particular population of P. ochraceus was found to consist alomost entirely of barnacles, primarily Tetraclita, Megabalanus californicus, and Balanus nubilus, for the simple reason that those are the prey items available on the wall. Although the behavior of individuals may appear to be erratic and random, when the movements of the total population are looked at, they fall into certain patterns. When divided into "upper" and "lower" zones, it was observed that indviduals in the upper zone predominantly move down, and those in the lower zone predominantly move up. As evidenced by results from concentrated 15 and 30 minutes watches, and 12 and 24 hour measurements, the majority of movement of P. ochraceus takes place during the high high tide and/or at night.