CCAMLR

A potential method is presented for combining data collected as part of the CCAMLR ecosystem monitoring programme (CEMP) into a single index for each of the predator, prey and environment parameters. The proposed method is based on the usual theory of multivariate statistics and takes into account the covariance between parameters. The power of the statistical procedure recently adopted by WG-EMM for identifying anomalies in CEMP parameters is examined by means of simulation tests. The power of the procedure to detect anomalies was found to fall to low levels once more than a few anomalous values have appeared in the data. An alternative procedure, using baseline mean and variance estimates was found to have consistently better statistical power regardless of the accumulation of anomalies. An approach to the further development of CEMP indices is outlined.

The properties of a method for detecting anomalous years in CCAMLR index series are discussed. In simple cases this method involves comparing a standardized residual with a critical value obtained on the assumption that the series being considered consists of random values from a constant normal distribution. This idea is extended to situations (a) where the series values are still normally distributed, but contain a linear trend and autocorrelation, and (b) where the series values are from some other constant distribution. For cases like (a) # is proposed that the standardized deviations from a fitted linear regression line are compared with a critical value that is obtained on the assumption that there is no autocorrelation. This test is shown to have good properties even when autocorrelation is present, at least according to one model For cases like (b) it is proposed that a Box-Cox transformation to normality is applied before testing standardized residuals. This test has good properties for data from a wide range of distributions. Some examples are given to illustrate the performance of the proposed methods under various conditions.

Data on Antarctic petrel Thalassoica antarctica population and demography monitoring at Svarthamaren, Dronning Maud Land from five field seasons between 1991/92 and 1996/97 is presented. The results of the population monitoring show that the number of pairs with chick or egg varied between 55,387-178,240 (mean 119,000). Assuming that about 10 % of the colony is situated in inaccessible parts outside the area covered by the monitoring system the mean number of pairs producing a chick each year is about 132,000. On average 52% of the reproductive fraction of the population breeds each year indicating that the total number of reproductive birds attached to the colony is approximately 510,000 individuals. Annual survival rates varied between 0.871-0.954 (mean 0.924). Our results suggest that a monitoring programme for breeding Antarctic Petrels should include estimation of mortality rates and breeding frequency in addition to the numbers of birds breeding.