CCAMLR

Three species of seals around Antarctica have shown quasi-cyclic patterns in some aspect of their biology: the age structure of crabeater seals (Lobodon carcinophagus) around the Antarctic Peninsula has shown strong cohorts separated by 4- to 5-yr intervals; juvenile leopard seals (Hydrurga leptonyx) have appeared in unusually large numbers at Macquarie Island, also at 4- to 5-yr intervals; and Weddell seals (Leptonychotes weddellii) in McMurdo Sound have undergone fluctuations in reproductive rate every 4-6 yr. Complex demodulation was used to compare patterns among these three data sets and with the Southern Oscillation Index (SOI). All of the seal data sets showed evidence of cyclical behavior when demodulated at a period of 5 yr. The Weddell seals were generally in phase with the SOI since the Weddell series began in 1970. The leopard seals and SOI were in phase in the 1960’s, but thereafter the SOI series led the leopard seal series by about one quarter of a cycle. The crabeater series was more complicated, but similarities with the other data sets also were seen. If these tentative observations are confirmed, they point to large-scale oceanographic variation, possibly related to the El Niño - Southern Oscillation (ENSO), as an important mechanism in Antarctic marine ecosystems.

The ability to determine the sex of Adélie penguins by discriminant analysis of morphometric parameters was examined for breeding birds of known sex at Bechervaise Island near Mawson Station, Antarctica (latitude 67°36’S, longitude 62°53’E). It was found that 89 % of birds could be correctly sexed by comparing the discriminant score D = 0.582 (bill length) + 1.12 (bill depth) + 0.219 (flipper width, cubitocarpal) with the mean discriminant score of 55.39. Males have a higher score and females a lower one. The sex of juvenile birds (identified by their white chins) cannot be determined by this method. The method is sensitive only where very accurate measurements are taken and it is recommended that the mean discriminant score be determined for a single operator and at each breeding colony to reduce these sources of variation. Further, it should be applied only to breeding birds. The probability of correctly identifying the sex of the birds can be increased by avoiding those with a discriminant score close to the mean. However, to be 100% certain of the sex of birds, 80% of the total measured sample would have to be discarded. In addition to the increased work load, this leads to serious bias in the resultant sexed samples. The usefulness of discriminant analysis for sex determination of Adélie penguins for applied monitoring studies is questioned.