Meeting Abstract

54.6  Saturday, Jan. 5  Factors influencing distribution and abundance of octopus inside and outside of a marine protected area in a kelp forest rocky reef ecosystem HOFMEISTER, J.K.K.; University of California, Berkeley jenkkhof@berkeley.edu

Anthropogenic influences on the marine environment can result in altered community interactions and food web dynamics. Most research about this topic focuses on keystone or apex predators, but studies focusing on mid-level predators can reveal interspecific competition and predator-prey interactions, resulting in a better understanding of how a certain ecosystem has been altered by anthropogenic activities. Octopuses are important mid-level predators but little is known about octopus population response ecosystem change. This study focused on the factors influencing octopus distribution and abundance inside and outside a marine protected area (MPA) on Santa Catalina Island, CA. It was hypothesized that octopus abundance would be greater in the non-MPA sites, as the removal of fish predators should relieve some predatory influence on their populations. Octopus, fish, lobster, and gastropod distribution and density surveys were completed in 10 sites during Jun-Aug 2012. Rock formation type and percent algae cover data were also collected. Contrary to my hypothesis, preliminary analysis of the data suggests that within similar rock formations, there are more octopuses inside the MPA than outside. Moray eels, a major predator of octopus, are more abundant outside the MPA, possibly explaining this result. Furthermore, when a variety of rock formations are included in the analysis, this trend disappears. This suggests a possible hierarchy of factors influencing octopus distribution in a rocky reef kelp forest, where habitat type is more important than predator abundance. This study highlights the complex interplay of ecological factors that influence where octopus are found in their environment, and calls for further research to understand how octopus will respond to a changing world.