CCAMLR

Diving animals offer a unique opportunity to study the importance of physiological constraint in their everyday behaviors. An important component of the physiological capability of any diving animal is it’s aerobic dive limit (ADL). The ADL has only been measured in a few species. The goal of this study was to estimate the aerobic dive limit from measurements of body oxygen stores and at sea metabolism. This calculated ADL (cADL) was then compared to measurements of diving behavior of individual animals of three species of otariids, the Antarctic fur seal, Arctocephalus gazella, the Australian sea lion, Neophoca cinerea, and the New Zealand sea lion, Phocarctos hookeri. Antarctic fur seals dove well within the cADL. In contrast, many individuals of both sea lion species exceeded the cADL, some by significant amounts. Australian sea lions typically dove 1.5 times longer than the cADL, while New Zealand sea lions on average dove 1.4 times longer than the cADL. The tendency to exceed the cADL was correlated with the dive pattern of individual animals. In both Antarctic Fur Seals and Australian sea lions, deeper diving females made longer dives that approached or exceeded the cADL (P

Spawning by Antarctic fish is generally considered to be seasonal and restricted to a brief period during the autumn and winter. Arising from this it has been assumed that the gonadal maturation cycle is also closely tracked to the time of year. The gonad maturation cycle of the mackerel icefish, Champsocephalus gunnari, was investigated using data collected during research surveys and from sampling the commercial fishery. Spawning appears to occur at the same time each year, but the timing of gonadal development is subject to a considerable inter-annual variation. The implications of this variation are discussed with respect to feeding conditions.

Mackerel icefish are widespread on the South Georgia shelf, Antarctica and have been subject to commercial fishing since the early 1970s. They are known to feed predominantly on krill. An index of condition which uses the ratio of the measured total mass to the estimated mass is show to provide a good indicator of local krill density. The index is likely to be little affected by the reproductive cycle unless there is high krill availability during the months around the spawning time and even then the effect is much less than the highest observed values The condition index responds rapidly to changes in hill density and therefore can provide indications of short term variations in krill availability. Condition index provides a useful proxy for krill density that is likely to be of considerable value in interpreting the results from ecosystem assessments such as that in progress under the auspices of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).

The relationship between krill abundance and predator performance is fundamental to an ecosystem based approach to resource management. We propose a method using krill sampled from the diet of predators to provide a length-frequency distribution of krill at times when it is possible to run automated ship-board acoustic systems but not to conduct scientific netting, i.e during logistic/re-supply operations. This will allow a robust estimate of krill abundance to be estimated from acoustic data. Changes in the length-frequency distribution of krill over a period of few weeks produced a 10 % difference in TS whereas simultaneous samples from predators and nets produced only a 1 % difference, illustrating the need for simultaneous length-frequency data. By integrating data from land-based predators directly with automated on board data collection systems it will be possible to gain important estimates of krill biomass at times of the season hitherto unavailable from ship-board scientific surveys.

This paper examines the foraging behaviour of Adélie penguin parents and the provisioning of their chicks during the guard and crèche stages of chick development. The differences, observed in three poor breeding seasons compared with six seasons where a higher fledging success was achieved, are highlighted. A continuous collection of data on foraging trip duration and meal mass (arrival weight minus departure weight) from birds of known breeding status and sex was obtained using an automated monitoring system. It is concluded that chicks during the guard stage are most vulnerable to a decreased availability of food and thus most susceptible to competition from a fishery.

During the XIII Italian Expedition to the Ross Sea in late spring and early summer (December-January 1997-98), for biological validation of hydroacoustic recordings, 35 net samplings were carried out. For all hauls both parameters: biological (length AT, sex and maturity stage of the gonads of the Euphausia superba) and acoustical (differences in volume back-scattering strength of krill aggregations MVBS at 38, 120 and 200 kHz) were examinated. Comparing the depth of the net and acoustic recordings during the hauls.
The surveyed area extended from 71° to 76°' S in latitude and from 164° E to 177° W in longitude. The aim of the paper is: (1) to compare the species/length composition of catch data and the one obtained by processing acoustic data, acquired during the net sampling; (2) to present density distribution maps of Euphausia superba and Euphausia crystallorophias obtained by processing acoustic data; (3) to analyse the structure of Euphausia superba population on the basis of biological variables, extracted from catch data;.
The analysis of the biological parameters seems to indicate statistically significant differences in them between the hauls, while within each haul the parameters are homogeneous. The maturity stage of krill in general increase with decreasing of latitude (from 76° to 71°S).
The analysis of acoustic and catch data indicate that: (1) the acoustic discrimination between the two predominant species, based on the multi-frequency method, is very close to the one based on net samplings; (2)The acoustic estimation of the krill mean length, based on the fluid sphere method, is pretty close (around 9%less) to the mean catch values; (3) The numerical abundance of the krill, estimated by the fluid sphere method, is 20-100 times higher than the one estimated from the catch.
The geographical biomass distribution of Euphausia superba and Euphausia crystallorophias, estimated acoustically, overlap in this period of year.