Presentation Title

The Diet of California Sea Lions (Zalophus californianus) prior to Recent Unusual Mortality Events

Faculty Mentor

Stephanie Nehasil, Mark Lowry, Alexandra Curtis, Kelly Govenar, and Carolyn Kurle, University of California, San Diego, CA and Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration, La Jolla, CA, University of California, San Diego, CA and Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration, La Jolla, CA

Start Date

18-11-2017 10:00 AM

End Date

18-11-2017 11:00 AM

Location

BSC-Ursa Minor 10

Session

Poster 1

Type of Presentation

Poster

Subject Area

behavioral_social_sciences

Abstract

The diet of California sea lions has been linked to their reproductive success. Prey availability and composition may in turn be influenced by oceanographic conditions. The diet of sea lions has been monitored over time by collecting scat samples four times a year from 1981 to 2009 at rookeries on San Nicolas and San Clemente Islands, which are part of the California Channel Islands. Hard part remains (i.e. cephalopod beaks and fish otoliths) are removed from the samples, then used to identify prey species and size. These long-term diet data show that certain prey species are commonly found in sea lion diets. While the sea lion population is not threatened, recent atypical increases in numbers of dead sea lion pups (Unusual Mortality Events or UME; 2013-2017) have prompted the need to better understand the mechanisms affecting prey availability and composition for sea lions near the Channel Island rookeries. Scat samples processed in the initial years of the UME show anomalies in the sea lions’ diet, however the diet in the years preceding the UME (2010-2012) remain unknown. We aim to determine a) if sea lion prey consumption was anomalous in the years preceding the UME and b) the timing (i.e. season and/or year) of a potential transition in diet from normal to anomalous. Given that sea lions showed high reproductive success during 2010-2012, we would expect their diet was normal during that time at both islands. This information is critical to understanding how marine mammals respond to changes in their environment, monitoring the health of marine mammal populations, and managing human impacts on marine mammals and their forage base.

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Nov 18th, 10:00 AM Nov 18th, 11:00 AM

The Diet of California Sea Lions (Zalophus californianus) prior to Recent Unusual Mortality Events

BSC-Ursa Minor 10

The diet of California sea lions has been linked to their reproductive success. Prey availability and composition may in turn be influenced by oceanographic conditions. The diet of sea lions has been monitored over time by collecting scat samples four times a year from 1981 to 2009 at rookeries on San Nicolas and San Clemente Islands, which are part of the California Channel Islands. Hard part remains (i.e. cephalopod beaks and fish otoliths) are removed from the samples, then used to identify prey species and size. These long-term diet data show that certain prey species are commonly found in sea lion diets. While the sea lion population is not threatened, recent atypical increases in numbers of dead sea lion pups (Unusual Mortality Events or UME; 2013-2017) have prompted the need to better understand the mechanisms affecting prey availability and composition for sea lions near the Channel Island rookeries. Scat samples processed in the initial years of the UME show anomalies in the sea lions’ diet, however the diet in the years preceding the UME (2010-2012) remain unknown. We aim to determine a) if sea lion prey consumption was anomalous in the years preceding the UME and b) the timing (i.e. season and/or year) of a potential transition in diet from normal to anomalous. Given that sea lions showed high reproductive success during 2010-2012, we would expect their diet was normal during that time at both islands. This information is critical to understanding how marine mammals respond to changes in their environment, monitoring the health of marine mammal populations, and managing human impacts on marine mammals and their forage base.