ALBERT

Description: Long-term temperature and current-meter records from moorings in the northern Canary Basin display strong current events with time scales between one and three months and large vertical scales of several thousand meters. The data are compared to hydrographic surveys in the area that show a meandering subtropical front. The strong current events are found to be related to the passage of the front through the mooring positions. An analysis of composite time series, for selected depths, indicates cases of westward and of eastward propagation of frontal meanders. The frontal pattern is also found in geopotential anomalies inferred from historical XBT data sets, suggesting that the front is a persistent feature of the density field. In two cases strong current events appear to be related to a Mediterranean Water lens.

Description: Giant petrels are the dominant scavenging seabird species in the Sub-Antarctic and maritime Antarctic ecosystems. They consume large amounts of penguin carrion, but also include significant numbers of seals, Antarctic Krill, Euphausia superba, and small petrels in their diets. Using results of detailed dietary studies at Bird Island, South Georgia, and qualitative data for other localities, notable variation in the quantitative impact of Giant petrels on their prey is revealed. Energy budgets of chicks are calculated from data on meal size and feeding frequency at all stages of growth. Differences in energy requirements between the Northern Giant Petrel, Macronectes halli, and the Southern Giant Petrel, M. giganteus, and between male and female chicks, are demonstrated. Published and unpublished data on numbers of giant petrels at known breeding sites are reviewed, and the present world breeding population is concluded to be ca. 8,600 pairs of M. halli and ca. 38,000 pairs of M. giganteus. Using survival and demographic data for South Georgia, total world non-breeding populations of ca. 26,000 and ca. 113,000 birds are calculated for M. halli and M. giganteus, respectively. The energy consumption of these populations in the breeding season is assessed and, taking into account geographical variation in diet, their impact on local ecosystems is evaluated. The approximations and assumptions of these estimates are discussed.

Description: Thirty seven juvenile specimens and one adult specimen of the cranchiid squid Mesonychoteuthis hamiltoni were captured by the opening and closing RMT8 net during RRS ‘Discovery’ cruise 100 (1979) in the Southern Ocean. The collection extends the size ränge of juveniles of this species previously described and illustrated. The small specimens resemble small juveniles of Galiteuthis glacialis, which also occur in most hauls, but are separated on the following characters : (a) M. hamiltoni lacks paired tubercles at the nuchal mantle fusion, (b) M. hamiltoni possesses a more capacious and thicker mantle, which is freer at the nuchal fusion and less constricted posterior to the opening; (c) juvenile M. hamiltoni up to a size of 26.5 mm (the largest in the present collection) have very small fins, while in G. glacialis of this size the posterior portion of the mantle has begun to extend into a tail and prominent fins appears; (d) M. hamiltoni has longer tentacles until it reaches a dorsal mantle length of approximately 25 mm. All specimens of M. hamiltoni were captured to the south of the Antarctic Convergence, and most were captured at depths between 20 m and 500 m apparently concentrated in the upper zone of ‘Warm Deep Water’ beneath the surface layer. Four newly hatched specimens were captured at 55°35’S between 20 and 500 m. The adult specimen was captured in a haul which had sampled a depth horizon from 2 000 m to 2 200 m.

Description: Seventeen advanced macrotritopus “larvae” from 7 to 15 mm mantle length were attracted to underwater lights in St. Croix, U.S. Virgin Islands. Their behavior was observed in situ, then seven were captured alive and one female was reared to an adult Octopus defilippi. The characteristic long arms of the planktonic young appear to function in flotation, feeding, crawling and defense. There is evidence that larger macrotritopus may be planktonic by night and benthic by day; thus the transition from a planktonic to benthic life may be controlled to ensure widespread distribution on to a suitable habitat. Morphological examination of 106 specimens from the Atlantic indicate that all macrotritopus “larvae” from this ocean are O. defilippi.

Description: A methodology is presented for obtaining egg masses from captive populations of the ommastrephid squid Illex illecebrosus and for incubating them intact under controlled conditions. Survival of rhynchoteuthion larvae for 9 days after hatching is the best reported to date, though it has not yet been possible to induce feeding. Factors critical to rearing success are discussed, e.g. tank size, stocking density, turbulence, light levels and photoperiod, as well as food type and concentration.

Description: The unique rhynchoteuthions of the ommastrephid squids are the smallest decapodan cephalopod hatchlings and have never been successfully reared. Based on anatomical and behavioural observations a mechanism of suspension feeding is proposed which depends on direct interception and inertial impaction on the mucus coated body surface. Mucus is transferred to the mouth area by ciliary motion and by observed cleaning behaviours. Suspension feeding is suggested to be a supplement to raptorial feeding but may be a critical "bridge" between small yolk reserves and the minimum development required for effective predation. Loss of ciliature through contact with vessel walls may prevent feeding in culture.

Description: The methods and results of the study of the tropho-dynamic relationships between 2 Diomedea albatrosses and the marine environment at South Georgia are described. They illustrate the technical and theoretical developments necessary to obtain certain empirical data essential for accurate assessments of the role of seabirds in marine ecosystems. Differences in breeding success during eight yr (consistent in D. chrysostoma, more variable in D. melanophris) are linked with important differences in breeding frequencies which affect the size and activities of populations at the breeding sites. Extensive dietary studies, based on sampling adults about to feed chicks, showed major inter-specific differences, resulting in chicks receiving meals of similar size and frequency but of different energy content. The frequency of chick feeding was determined initially by daily and 3-h weighing. Recently automatic equipment has recorded weights every 10 min, giving the frequency and size of meals and resulting digestive performances of the chicks. Experiments involving exchanging chicks between the two species were combined with new methods for analyzing growth curves. They showed that, while there was a species-specific genetic component to growth, the overall rate could be significantly modified by the nature of the diet. The slower growth rate of D. chrysostoma chicks, and the species’ diet, are probably important factors affecting breeding frequency. Adult feeding performance is being studied by devices recording simple activity budgets at sea. Preliminary results are described and projected work linking this with the automatic weighing equipment and with assessment of foraging energy costs is outlined.

Description: The energy requirements and prey consumption of the rapidly expanding South Georgia population of Antarctic Fur Seals, Arctocephalus gazella, are estimated, using information on diet, population structure, activity patterns, and energy budgets and variations in these with sex and season. All quantitative information on diet is reviewed. Breeding female Fur Seals mainly take Antarctic Krill, Euphausia superba. This predominates also in the summer diet of males but fish (mainly Champsocephalus gunnari) and squid are also eaten. Fish is more important to males in winter. Life tables are used to determine the proportion of each age-class in the population, and especially to estimate the size of that portion of the immature stock which does not appear ashore. Energy costs of adult males are assessed from attendance data and age-specific weights. Female energy budgets are calculated from extensive data on the duration of periods ashore and foraging trips to sea together with information on activity budgets at sea. Pup energy consumption is calculated from body weight and growth data. A summer food consumption of 1.1 × 106 t is divided between juvenile males (39%), adult females (31%), adult males (22%) and juvenile females (8%). In winter, when females are absent, juvenile (67%) and adult males (33%) consume 0.4 × 106 t. Krill forms 69% of the annual consumption, fish 19% and squid 12%. The main peaks of demand are in October (all adults feeding at sea), January-February (rapidly growing pups being reared) and April—May (most of population, including weaners, feeding at sea). From data on diet and foraging ranges and depths, the main natural competitor of the Antarctic Fur Seal is the Macaroni Penguin, Eudyptes chrysolophus; significant competition with a developed Krill fishery would be expected. Continuing commercial exploitation of fish, especially C. gunnari, may influence male Fur Seal populations, particularly in winter.

Description: This paper reviews the current state of knowledge of the food habits of the poorly known small cetaceans of the Southern Ocean and presents new information obtained through a study of stranded specimens in Tierra del Fuego. In the Antarctic and Sub-Antarctic, food data are available for only 10 of the 22 species present. Adding to this all the food records known from the South Temperate Zone south of 30° S, there is still no information at all for 5 species (Mesoplodon layardii, M. hectori, M. bowdoini, Cephalorhynchus eutropia and Phocoena dioptrica); that of 8 species is based on fewer than three samples, and more than 10 samples are available for only 2 species (Orcinus orca and Cephalorhynchus commersonii. Since these cetaceans are among the larger animals of the Southern Ocean, their role in the food web of the ecosystem cannot be determined until more information is available.

Description: Rhynchoteuthion larvae of three species of ommastrephid squids from Hawaiian waters were identified, and aspects of their ecology examined. Important taxonomic characters for field Identification include the number and location of photophores, length of the proboscis (fused tentacles), size at which the proboscis completely divides and the relative sizes of the suckers on the proboscis tip. Other taxonomic characters include sucker structure and chromatophore patterns. Variation among species were found in both temporal and vertical distributions.

Description: While carrying out a systematic revision of the pelagic squid genus Octopoteuthis, the author examined 146 “larval” specimens of the genus from museum sources worldwide. Individuals could not be separated into species but morphometric and meristic characters were examined giving information on ontogenetic development. Specimens ranged in size from 1.3 to 27.0 mm dorsal mantle length (DML) and represented locations in the Atlantic, Pacific and Indian Oceans and also the Mediterranean Sea. Captures were made with a variety of trawls and plankton nets. The deepest record from a closing net was 1 200 m using a MOCNESS system. The largest group examined totalling 105 individuals was collected in the North Atlantic. In the Atlantic the highest larval occurence was found to be in March, April, and June (which may reflect higher sampling pressure in those months) but specimens were obtained in all months except January and December. Low numbers in each of the other oceans prohibited an evaluation of yearly larval distribution.

Description: Larval squid were sampled in three surveys off the eastern Australian coast in January, March and May 1983. Ommastrephid larvae were abundant and occurred at over 90 % of stations. Although Identification to species level has not so far been possible for the majority of specimens, general patterns of distribution with respect to latitude and bottom depth are presented.