River Otter Diet and Predation Project


Project status: A peer-review article has been published. (5/2014)

SeaDoc funded a River Otter diet and predation study by Monique Lance of the Washington Department of Fish & Wildlife. 

The study aims to describe the diet of river otters and investigate the potential effect they have on rockfish and salmon populations in the San Juan Islands.

Rockfish and salmon are currently listed under the Federal Endangered Species Act. Because of the dramatic decline in these species over the past several decades, Marine Protected Areas have been created to assist in their recovery. 

However, little attention has been paid to how predators respond to increased prey densities. Therefore it's important to investigate the diet of potential predators. 

Otter scat samples were collected in the spring, summer and fall of 2008 on Fidalgo, San Juan and Orcas Islands. The scat samples were cleaned and invertebrates in them have been identified in a previous project. This project now allows for the analysis of fish remains in the scat, as well as examinations of spatial variation among the project sites and temporal variations through 2008. Data will be compared to diet data from Alaska and British Columbia, and also to the diet of various other predators, including harbor seals and Steller sea lions.

Photo by Michael Ransburg: Creative Commons license.