Dailey and Vogelbein: Parasite fauna as stock indicators of Antarctic whales 



363 



recorded the nematode Anisakis simplex only from sei 

 whales of the "Notalia Zone" (northern boundaries of 

 whaling sectors). Another nematode, Crassicauda 

 delamureana Skrjabin, 1966, was reported only in the 

 "Notalia Zone" of sectors II and III; the acantho- 

 cephalan Bolbosoma tuberculata Skrjabin, 1970 only in 

 the South Atlantic; Bolbosoma balaenae (Gmelin, 1970) 

 only in sectors IV and V; and the trematode Lecitho- 

 desmus goliath (van Beneden, 1858; Braun, 1902) was 

 confined to the southeast coast of South America. The 

 trematode Ogmogaster antarcticus Johnston, 1931 was 

 recorded only from sectors I and V, while the larval 

 cestode P. delphini parasitized sei whales only in sec- 

 tor V, south of New Zealand. Although prevalences of 

 infection are low in all of the above cases, as more in- 

 formation is gathered these helminths may help to iden- 

 tify local, isolated stocks of whales. 



Other helminths such as the cestodes T. affinis and 

 P. grandis have a limited geographical distribution in 

 sei whales, but the fact that these species are poly- 

 xenous extends their known range significantly. These 

 helminths are consequently of limited potential value 

 in identifying sei whale stocks. 



Differences in the helminthofaunal diversity are evi- 

 dent between three host stocks captured in sectors V, 

 VI, and I during 1976-77 (Fig. 2). It is probable that 

 regions of upwelling in the coastal waters of New 

 Zealand and Australia provide sufficient nutrients to 

 support a greater diversity of free-living organisms 

 than would be expected in the open Pacific Ocean. Con- 

 sequently, a greater diversity of prey species (hence 

 intermediate hosts) is likely to be exploited in the 

 coastal waters, inflicting these sei whale stocks with 

 a higher diversity of helminths. 



The helminth fauna of the Antarctic minke whale has 

 been poorly studied. The only prior investigation is that 

 of Skrjabin (1975) who examined six hosts from the 

 Balleny Island region (sector V) and sector IV, and 

 found them uninfected. Our study is the first to ex- 

 amine a large number of Antarctic minke whales. The 

 number of helminths found infecting this host was very 

 few (Tables 1, 3). The only significant infection is that 

 of Tetrabothrius sp. With this limited information 

 available, Antarctic stocks are presently indistinguish- 

 able with respect to their helminth fauna. 



Skrjabin (1975) believes that this poor helminth fauna 

 is due to the minke whales' feeding habits. The diet of 

 the southern minke whale is more restricted than that 

 of other Antarctic whales. Ohsumi et al. (1970) reported 

 that most minke whales congregate south of the Ant- 

 arctic Convergence and feed almost exclusively on 

 Euphasia superba. Stomach samples occasionally con- 

 tained small amounts of other prey species. This host 

 penetrates the furthest south of all the whales and in- 

 habits the ice pack close to the Antarctic continent. 



It feeds almost exclusively on E. superba which are not 

 found to be infected with larval helminths (Kagei 1974, 

 Kagei et al. 1978). 



The known helminth fauna of the sperm whale is 

 presently comprised of 18 species (Table 6) which may 

 be subdivided into several distinct components. Two 

 helminths, the larval cestode Phyllobothrium delphini, 

 and the stomach nematode Anisakis physeteris, occur 

 at very high prevalence and intensity throughout the 

 Antarctic. Since these parasites have a cosmopolitan 

 distribution in odontocetes, they are probably useless 

 in distinguishing between southern sperm whale stocks 

 in the longitudinally defined IWC sectors of the Ant- 

 arctic. However, P. delphini may be important from 

 a latitudinal aspect. For example, Walker (1987) found 

 latitudinal differences in the occurrence of this parasite 

 in Dall's porpoise Phocenoides dalli True, 1885 taken 

 in the northern North Pacific and Bering Sea. The 

 absence of P. delphini in B. aeutorostrata and the very 

 low frequency of occurrence in B. borealis along with 

 its ubiquitous occurrence in the sperm whale tend to 

 substantiate the more pronounced seasonal north- 

 south movement of the Antarctic sperm whale stock(s) 

 into temperate waters. Best (1974), Gambell (1972), and 

 Gaskin (1971) all report extensive migrations ranging 

 from tropical latitudes (north of 35 °S) to above 60 °S 

 for males forming "bachelor" herds. Best (1974) cal- 

 culated from mark returns that the average annual 

 movement was approximately 850 nautical miles 

 (1410km) for males, and 372 (620km) for females. 



Acanthocephalans belonging to the genus Coryno- 

 soma may, however, be of some value in distinguishing 

 the Indian Ocean-Antarctic stocks of sperm whales 

 from those in the Atlantic and Pacific- Antarctic (Fig. 

 4). Corynosoma mirabilis was found in 18 large male 

 sperm whales from Africa to Australia (sectors III, 

 IV, and V) in the Indian Ocean. This species was found 

 only between 40° and 60°S latitude. In the 1976-77 

 material, whales taken in the southern portion of sec- 

 tor VIII were infected with immature C. bullosum. Sex- 

 ually immature Corynosoma singularis are reported 

 from a single sperm whale captured in the southwest- 

 ern Atlantic Ocean (sector I) (Skrjabin 1971) and also 

 as adults in a leopard seal from the Balleny Islands. 

 Despite the fact that these acanthocephalans attain sex- 

 ual maturity only in the Phocidae, these larval forms 

 in the sperm whale may have the possibility of serving 

 as regional stock indicators. 



Local variations in the helminth diversity of sperm 

 whales captured in sector VIII during 1976-77 are 

 illustrated in Figure 3. Variable infections are noted 

 between male and female sperm whales. It is difficult 

 to say whether these distributional peculiarities are 

 coincidental or real due to small sample sizes. Assum- 

 ing that they are real, they become very difficult to 



