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.