Diets of Steller and California sea lions determined from scat collections in northwest Washington during 2010-2013 with genetic identification of salmon species

Published: 21 January 2022| Version 2 | DOI: 10.17632/3f5fmk8pp2.2
Jonathan Scordino,
, Cydni Marshall,
, Randall James, Daniel Shay


The attached excel file contains data from an analysis of the diet of Steller and California sea lions conducted in northwest Washington during 2010 through 2013. The data presented in this submission updates the data provided by Scordino et al. (2001) with new additional analyses on the salmon eaten by Steller and California sea lions. Salmon bones were sorted into three size classes (small, medium, and large) and were provided to the Institute of Science and Technology at North Central High School in Spokane, Washington for genetic analysis to determine the species of salmon consumed by the sea lions. The excel file also contains information on the sites at which scat samples were collected and data from our analysis of genotyping errors. Scordino, Jonathan; Akmajian, Adrianne; Riemer, Susan (2021), “Steller and California sea lion count and diet data in northwest Washington, 2010-2013”, Mendeley Data, V1, doi: 10.17632/npdzxcsfh9.1


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We collected Steller and California sea lion scat samples from haulouts in northwest Washington from 2010 through 2013. Haulout sites where scat was collected include Tatoosh East, Tatoosh Cut, Guano Rock, East Bodelteh Island, West Bodelteh Island, Carroll Island, and Sea Lion Rock. Scat samples were only collected from sites in which 95% or more of the sea lions present were composed of the target species. Scat samples were collected following the techniques described by Lance et al. (2001). Our goal was to collect 30 scat samples from Steller sea lions each month and 50 scat samples from California sea lion each season during the study. Scat samples were cleaned by either placing the sample in a paint strainer bag and washing in a residential style washing machine or by washing the sample through nested sieves. Cleaned prey hard parts were stored in isopropyl alcohol and later dried. All prey hard part structures (i.e. vertebrae, otoliths, gill rakers, and beaks) were used for identifying the prey to the lowest taxonomic level possible. Prey were identified by Susan Riemer of Oregon Department of Fish and Wildlife by examining prey hard parts under a dissecting microscope and comparing to a reference collection of known prey specimens from the Eastern North Pacific and adjacent estuaries. Some species have very distinct bones for each species within a family whereas others, like rockfish and salmon, have very similar bone structures for all species within a family. As a result, some species are identified to the species level and others to higher taxonomic levels. We have presented our prey data with a 1 for presence in each scat sample for all taxon identified. We have also grouped prey by prey family, or to higher taxonomic order where applicable, and marked these grouped identification with bold font. Salmon bones could not be identified to species based morphological characteristics of recovered bones. To determine the species of salmon consumed, we conducted real-time PCR to identify salmon bones to species using methods developed by Rasmussen Hellberg et al. (2010). Genetic analysis was conducted at the Institute of Science and Technology at North Central High School in Spokane, Washington. We evaluated if our genotyping error rate by providing a blind sample of 15 salmon samples of known species to the Institute of Science and Technology. Thirteen of the 15 samples had amplified sufficiently for identification and all 13 were identified accurately. A manuscript presenting our analysis of the data in this submission will be submitted to the journal Fishery Bulletin in December 2021.


Animal Foraging, Marine Mammal, Foraging Behavior, Salmonid Fish, Fishery Ecology