Table 5. — Causes of pup mortality on study area 1, Reef 

 Rookery, St. Paul Island, 28 June to 15 August 1966 

 and 1967 



Primary cause of death 



1966 



1967 



1966 1967 



Number 



Malnutrition 67 



Liver damage-multiple hemor- 

 rhage-perinatal complex... 4 



Hookworm disease 24 



Trauma 18 



Infection 15 



Miscellaneous 4 



Undetermined 10 



Subtotal 142 



Unsuitable for examination.. 10 



Total 152 



32 



Percent 



44.1 40.0 



on fur seals since 1962 has been a lack of 

 lesions in the liver. The associated bilateral 

 ocular hemorrhage (20 percent of the cases) is 

 also new in fur seal pathology. Simple trauma 

 does not account for the sudden increase in 

 the number of cases and the unique syndrome 

 associated with this disease. The likelihood of a 

 predisposition to liver rupture and hemorrhage 

 seems strong. Microbiological and histological 

 studies of liver and other tissues are underway. 



This disease of fur seals may be new but is 

 more likely a sudden increase in a condition 

 that occurred at such a low level in the past 

 that it was not recognized. There was not suf- 

 ficient opportunity for recognition because 

 early pup mortality from late June to mid- July 

 has been studied in only 3 years-- 1958, 1966, 

 and 1967. ! 



Table A- 11 shows the lesions and circum- 

 stances associated with the cases observed in 

 1964, 1966, and 1967.2 



3. Hookworm disease. Investigators have 

 long believed, without quantitative evidence, 

 that the death rate from hookworm disease 

 varied from rookery to rookery. Table 4 shows 

 a striking difference between area 3, with a 

 death rate of 32.7 percent from hookworm 

 disease, and areas 1 and 2, with rates of 5.0 

 and 1.9 percent. We cannot explain this varia- 

 tion. The death rate from hookworm disease 

 on area 1 was 8.1 percent in 1964, 17.7 per- 

 cent in 1966, and 5.0 percent in 1967. 2 



4. Enteritis. In previous years necrohemor- 

 rhagic enteritis has been seen mostly as a 



1 Studies of pup mortality in 1964 were begun on 9 July. 



2 Includes deaths to 22 August in 1964 and 1966, and to 

 15 August In 1967. 



previously 

 complica- 

 a primary 



terminal condition in emaciated pups; there 

 were 27 such cases in 1967. We assumed that 

 enteritis developed as a result of gut stasis 

 and lower resistance to infection brought about 

 by malnutrition. In most cases this explanation 

 is still the most logical; however, in 1967 

 enteritis was the only important lesion in four 

 pups whose body condition was otherwise good. 

 One other pup, with severe enteritis, had a 

 generalized systemic infection. We isolated two 

 species of bacteria, Proteus mirabilis and 

 Escherichia coli, from the small intestines of 

 this pup and two of the other four cases of 

 enteritis. The same organisms were isolated 

 from one of several artifically reared pups 

 that had died of enteritis. Proteus mirabilis 

 had been isolated from captive pups, 3 from a 

 rookery pup that died of malnutrition and 

 secondary necrohemorrhagic enteritis (Keyes, 

 1965), and from flipper abscesses of a rookery 

 pup (U.S. Fish and Wildlife Service, Bureau of 

 Commercial Fisheries, 1969). The Proteus 

 organism had not been isolated 

 from cases in which enteritis, or 

 tions of an enteric infection, was 

 cause of death. 



5. Stillbirths. Of the 232 pups examined, 

 17, or 7.3 percent, were stillborn (had never 

 breathed). Eleven of these were included 

 among those classified as liver damage- 

 multiple hemorrhage-perinatal complex. An 

 occasional pup drowns in embryonal fluid when 

 the fetal membranes over the head fail to 

 break. In other cases, the pups are dead before 

 parturition. 



6. Undetermined causes and pups unsuit- 

 able for examination. In 1967, we picked up 

 dead pups for autopsy every 2d or 3d day 

 instead of daily, as in 1964 and 1966. The per- 

 centage of pups classified as unsuitable for 

 determining cause of death in 1967 was nearly 

 double that of 1966 (table 5); 26 percent of the 

 232 pups examined had advanced post mortem 

 degeneration (table A- 12). 



Seasonal and annual trends in pup mortality . -- 

 Figure 7 compares total numbers of pup deaths 

 throughout each season in 1964, 1966, and 1967. 

 Peaks of mortality occurred at about the same 

 time in each of the 3 years. The peaks coincide 

 with the peak of births, the early deaths from 

 injury, and the lag necessary for deaths from 

 malnutrition, hookworm disease, and infection 

 to occur (table A- 12). 



3 Mark C. Keyes. 1964. Research in fur seal mortality, 

 St. Paul Island, Alaska, 8 July to 24 September 1963. Bu- 

 reau of Commercial Fisheries Marine Mammal Biological 

 Laboratory, Seattle, Wash. [Processed, 140 pp.] 



