Sea Lion Diet Data

California sea lions pup and breed at four of the nine Channel Islands in southern California. Since 1981, SWFSC MMTD has been conducting a diet study of sea lions at San Clemente Island (a small rookery) and San Nicolas Island (a large rookery). Information on the diet of sea lions is obtained from analyzing scats (i.e., fecal samples) and spewings (i.e., vomitus) collected at those two rookeries in January (winter), April (spring), July (summer), and October (autumn). Otoliths (a crystalline structure within the ear organ) from fish and beaks (mandibles composed of chitin) from cephalopods are recovered from the samples by washing each sample through sieves of varying mesh size. Otoliths and beaks, which are shaped and sized differently for each species of fish and cephalopod, respectively, are used to identify and enumerate fish, and cephalopods consumed by sea lions. Also, otoliths and beaks are measured for estimating size of prey being consumed by sea lions.

The objectives of the sea lion diet study being conducted are to:

1) Identify prey species being consumed by sea lions in order to determine which are most important to the sea lion population. Prey species are identified by hard parts, such as fish otoliths and squid beaks found in scats. See the recently published Photographic Catalog of California Marine Fish Otoliths: Prey of California Sea Lions (Zalophus californianus).

2) Monitor seasonal, annual, and multi-year variability in consumption of prey species.

3) Determine if dietary changes can be used to signal when the population reaches carrying capacity,

4) Estimate consumption by the sea lion population.

5) Use sea lion diet data as a fishery-independent index of abundance for commercial species of fish and squid.

San Nicolas Island

San Clemente Island

When resources are available to make data accessible; in interim, contact SWFSC MMTD.

FISMA Controls are in place to protect stored data from unauthorized access and/or disclosure.

User must read and fully comprehend the metadata prior to use. Acknowledgement of NOAA SWFSC, as the source from which these data were obtained, in any publications and/or other representations of these data is requested. The user is responsible for the results of any application of these data for other than its intended purpose.

data representative of animals feeding within distance of the collection sites on Channel Islands

All data have been entered carefully and double-checked by a single PI

FISMA Controls are in place to protect stored data from unauthorized access. Data are backed up on a daily basis on a local area network and, in some cases, external hard drives as well. Data are also backed up to tape and stored at a remote site for retrieval in case recovery is needed from these off-site media.

Scat samples collected in field are stored in freezer, then thawed prior to processing. Each scat sample is given a code number, then washed through sieves from which hard-parts (fish otoliths and cephalopod beaks) are collected. Prey identified and enumerated from prey hard-parts. Data entered onto Microsoft Excel worksheets, then transferred to Microsoft Access database. Queries are used to extract data for analysis. "Analyze program" written by Robert Holland summarizes queried data.