Graduation Date

Spring 2020

Document Type



Master of Science degree with a major in Biology

Committee Chair Name

Paul Bourdeau

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Erik Jules

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Brian Tissot

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Joe Tyburczy

Fourth Committee Member Affiliation

HSU Faculty or Staff

Subject Categories



Organisms serve as prey to a variety of predators within natural systems, detecting threats through physical and chemical means. While predator feeding behavior is also affected by the presence of other predators, it is unclear whether differing modes of detection have similar effects on predator feeding behavior. In rocky intertidal zones in northern California, the California mussel (Mytilus californianus) is a competitively dominant foundation species consumed by a variety of predators. I quantified the individual and combined effects of ochre star (Pisaster ochraceus) and rock crab (Romaleon antennarium) predation on mussels by implementing mussel caging experiments at three field sites in northern California and through laboratory feeding trials. I also compared the effects of chemical and physical competitor detection and elevated sea water temperatures on crab and sea star feeding behavior in laboratory feeding trials. I found that in the field mussel predation on vertical surfaces was attributed to seas stars. Further, on horizontal surfaces where mussels where accessible to both predators, predation was dominated by crabs, suggesting that crabs are better competitors and the physical presence of crabs potentially reduces sea star predation. I also found that the chemical detection of crabs increased sea star feeding rates, while physical detection decreased it. Additionally, elevated water temperatures only affected crabs, causing them to increase their feeding rates. Taken together my results suggest that mussels are at greater risk on rocky shores were crabs are present and will likely experience greater predation risk in the future under warmer sea water temperature conditions attributed to climate change.

Citation Style



Thesis/Project Location