WHITE SHARK PREDATION ON PINNIPEDS 

 IN CALIFORNIA COASTAL WATERS 



White sharks, Carcharodon carcharias, prey on 

 various fishes, sea turtles, whales, dolphins, and 

 on several species of pinnipeds (Allen 1880; Elli- 

 ot 1881; McCormick and Allen 1963; Davies 1964; 

 Nishiwaki 1972; Ellis 1976; Ainley et al. 1981; 

 MeCosker 1981). Data on pinnipeds preyed upon 

 by sharks in California waters are meager and 

 many aspects of the predator-prey relationship 

 are unknown. 



Four types of evidence indicate that sharks 

 prey on pinnipeds: 1) Pinniped remains in the 

 stomachs of dead sharks, 2) observation of seals 

 with injuries inflicted by large sharks, 3) obser- 

 vation of shark attacks on seals, and 4) the pres- 

 ence of sharks near seal rookeries at a time when 

 seals are present. We report evidence of the first 

 two kinds regarding shark predation on north- 

 ern elephant seals, Mirounga angustirostris, and 

 harbor seals, Phoca vitulina. 



Methods 



Five white sharks caught in southern Califor- 

 nia waters in 1975 and 1976 and two white 

 sharks that washed ashore in central California 

 in 1977 and 1978 were examined. The fresh dead 

 sharks were weighed, measured, and their sex 

 determined. Stomachs were dissected out and 

 contents identified, and in some cases, weighed 

 and measured (Table 1). 



From 1968 to 1980, shark-bitten elephant seals 

 on Ano Nuevo Island and the adjacent Ano 

 Nuevo Mainland in central California were 



counted, photographed, and identified individu- 

 ally, and their behavior was monitored. This was 

 accomplished during daily censuses conducted 

 each breeding season from December to mid- 

 March and during weekly censuses conducted 

 during the remainder of the year. Only seals with 

 fresh wounds judged by their pink or bloody 

 appearance to be less than a few days old were in- 

 cluded in the sample. This gives us confidence 

 that our subjects were injured near the study 

 area. We did not census animals with old scars or 

 healed injuries, whose origins were difficult to 

 ascertain. Shark injuries were differentiated 

 from other wounds, caused by boat propellers or 

 intraspecific fighting, by their oval shape and 

 the jagged serrations caused by the predator's 

 sharp teeth. Both slight and serious wounds were 

 included. Slight wounds consisted of superficial 

 tooth punctures or scrapes across the skin; seri- 

 ous wounds involved deep bites and tears. Seri- 

 ously wounded seals had large flaps of flesh 

 exposed or chunks of flesh missing. The di- 

 mension of bites was measured on a few dead 

 seals. 



We marked and followed 11 females who sus- 

 tained moderate to severe shark wounds when 

 pregnant just before arriving on the island to 

 give birth. Their pups were marked at birth and 

 the pair was observed until the filial relationship 

 ended. Northern elephant seal females give birth 

 within a week after arriving on the rookery. A 

 female nurses her pup daily for about 4 wk before 

 weaning it and returning to sea (Le Boeuf et al. 

 1972). 



A similar search for shark-bitten harbor seals, 

 which breed at Ano Nuevo Island and numerous 



Table 1.— Stomach contents of white sharks collected off the California coast from 1975 to 1978. Specimens 

 1-5 were collected by Sea World of San Diego, no. 6 by K. Skaug and M. Riedman, and no. 7 by an anonymous 

 fisherman. 



Specimen 

 number 



Date of 

 collection 



Location 



Sex 



Total 



length 



(m) 



Weight 



of shark 



(kg) 



Stomach contents 



Anterior portion of stomach contained har- 

 bor seal remains (18.2 kg). Posterior 

 stomach held unidentified pinniped. 



A 4-in patch of pinniped pelage 



Harbor seal, well digested. 



Skull and posterior portion of a juvenile ele- 

 phant seal, plus large amounts of fur and 

 digested material. 



Nearly digested Bulk suggested a large 

 animal, probably a marine mammal. 



Approximately one-third of a recently eat- 

 en 4-yr-old male elephant seal. 



The head of a harbor seal 



FISHERY BULLETIN: VOL. 80. NO. 4. 1982. 



891 



