Laugan Miller

Jim Spickard

EVST Research Methods



Effects of predators on sea urchin density and habitat use in a southern California kelp forest


Kelps form the base for many ecosystems by providing safe places for prey to hide. Sea urchins are disturbing these kinds of ecosystems by preying on the kelps. Researchers wanted to look at the possible effects of predators consuming the sea urchins and dropping their population numbers to stop kelp deforestation. While normally sea otters prey on urchins this research looked at an environment with sheepheads and lobsters as top predators. In this ecosystems the predators had to be a certain size in order to break the sea urchins apart which then prompted smaller predators to eat the scraps. This means that even though there might be an area with a heavy population of predators only a few can prey on the urchins and so they probably wouldn’t be able to control their population levels. This lead to researchers observing that urchin mortality rates were lowest were urchin populations were highest. These predators are unable to control the population of sea urchins. What to look at next would be what is limiting these predators sizes like overfishing and what introducing other predators would do to the ecosystems. What could also be helpful is other strategies that researchers have found worked to reduce sea urchin population sizes.

Nichols, Kathryn D., et al. “Effects of Predators on Sea Urchin Density and Habitat Use in a Southern California Kelp Forest.” SpringerLink, Springer, 24 Apr. 2015,

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