Trophodynamics of krill and its potential role in blue whale feeding in the Perth Canyon, south-east Indian Ocean

Migrating blue whales along the Western Australian coast exhibit feeding behaviour within the Perth Canyon, which is an area of high krill abundance, particularly for Euphausia recurva. The importance of krill in marine food webs has led to a number of trophodynamic studies investigating their fatty acid and stable isotope compositions. In the south-east Indian Ocean, the suppression of upwelling by the dominant Leeuwin Current results in relatively oligotrophic waters, particularly during autumn and winter. Oligotrophic waters tend to be dominated by small autotrophic flagellates (i. e. dinoflagellates) and cyanobacteria. We relate biochemical data obtained for E. recurva, as well as Stylocheiron carinatum and Pseudeuphausia latifrons with their potential food source, phytoplankton, and one of their potential predators, the endangered pygmy blue whale (Balaenoptera musculus brevicauda) sampled in the Perth Canyon. Fatty acids of all three krill species were dominated by polyunsaturated fatty acids (PUFA; ~50%) largely comprised of omega-3 PUFA, which is typical for krill. The high docosahexaenoic acid (DHA) to eicosapentaenoic acid (EPA) ratio reflects a dinoflagellate, rather than a diatom diet, and the high oleic acid (18: 1 9) to vaccenic acid (18: 1 7) ratio is indicative of an omnivorous diet. Stable isotope analysis positions E. recurva as a first, possibly second order consumer (5. 8 - 8. 4 15N)and phytoplankton as the likely source of carbon (-18 to -24 13C) .The fatty acid composition of krill did not match that of the surface phytoplankton sampled, which was low in PUFA and more reflective of degraded and detrital material. This suggests that krill are not feeding at the surface, and may feed closer to the deep chlorophyll maximum. The outer blubber layer sampled from the pygmy blue whale was high in monounsaturated fatty acids (MUFA, 58%) rather than PUFA, and did not reflect the krill fatty acid composition. However, the high DHA to EPA ratio in the blubber indicated a diet originating from dinoflagellates, as found for krill. Stratification of fatty acids across blubber layers is common for marine mammals and the outer blubber layer for some species has been found to not accurately reflect the diet of the animal

Past and present distribution, densities and movements of blue whales <i>Balaenoptera musculus</i> in the Southern Hemisphere and northern Indian Ocean

1Blue whale locations in the Southern Hemisphere and northern Indian Ocean were obtained from catches (303 239), sightings (4383 records of =8058 whales), strandings (103), Discovery marks (2191) and recoveries (95), and acoustic recordings.2Sighting surveys included 7 480 450 km of effort plus 14 676 days with unmeasured effort. Groups usually consisted of solitary whales (65.2%) or pairs (24.6%); larger feeding aggregations of unassociated individuals were only rarely observed. Sighting rates (groups per 1000 km from many platform types) varied by four orders of magnitude and were lowest in the waters of Brazil, South Africa, the eastern tropical Pacific, Antarctica and South Georgia; higher in the Subantarctic and Peru; and highest around Indonesia, Sri Lanka, Chile, southern Australia and south of Madagascar.3Blue whales avoid the oligotrophic central gyres of the Indian, Pacific and Atlantic Oceans, but are more common where phytoplankton densities are high, and where there are dynamic oceanographic processes like upwelling and frontal meandering.4Compared with historical catches, the Antarctic (‘true’) subspecies is exceedingly rare and usually concentrated closer to the summer pack ice. In summer they are found throughout the Antarctic; in winter they migrate to southern Africa (although recent sightings there are rare) and to other northerly locations (based on acoustics), although some overwinter in the Antarctic.5Pygmy blue whales are found around the Indian Ocean and from southern Australia to New Zealand. At least four groupings are evident: northern Indian Ocean, from Madagascar to the Subantarctic, Indonesia to western and southern Australia, and from New Zealand northwards to the equator. Sighting rates are typically much higher than for Antarctic blue whales.6South-east Pacific blue whales have a discrete distribution and high sighting rates compared with the Antarctic. Further work is needed to clarify their subspecific status given their distinctive genetics, acoustics and length frequencies.7Antarctic blue whales numbered 1700 (95% Bayesian interval 860–2900) in 1996 (less than 1% of original levels), but are increasing at 7.3% per annum (95% Bayesian interval 1.4–11.6%). The status of other populations in the Southern Hemisphere and northern Indian Ocean is unknown because few abundance estimates are available, but higher recent sighting rates suggest that they are less depleted than Antarctic blue whales.</li

Water temperature correlates with baleen whale foraging behaviour at multiple scales in the Antarctic

How baleen whales locate prey and how environmental change may influence whale foraging success are not well understood. Baleen whale foraging habitat has largely been described at a population level, yet population responses to change are the result of individual strategies across multiple scales. This study aimed to determine how the foraging behaviour of individual whales varied relative to environmental conditions along their movement path. Biotelemetry devices provided information on humpback whale (Megaptera novaeangliae) movement at two spatial scales in East Antarctica, and a mixed modelling approach was used at a medium scale (tens of kilometres) to determine which environmental factors correlated with a change in foraging behaviour. Water temperature was linked to a change in foraging behaviour at both spatial scales. At the medium scale, warmer water was associated with the resident state, commonly assumed to represent periods of foraging behaviour. However, fine-scale analyses suggested that cooler water was associated with a higher feeding rate. Variation in whale foraging behaviour with changes in water temperature adds support to the hypothesis that whales may be able to track environmental conditions to find prey. Future research should investigate this pattern further, given the predicted rise in water temperatures under climate-change scenarios

A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). CAPRIE Steering Committee

Many clinical trials have evaluated the benefit of long-term use of antiplatelet drugs in reducing the risk of clinical thrombotic events. Aspirin and ticlopidine have been shown to be effective, but both have potentially serious adverse effects. Clopidogrel, a new thienopyridine derivative similar to ticlopidine, is an inhibitor of platelet aggregation induced by adenosine diphosphate. METHODS: CAPRIE was a randomised, blinded, international trial designed to assess the relative efficacy of clopidogrel (75 mg once daily) and aspirin (325 mg once daily) in reducing the risk of a composite outcome cluster of ischaemic stroke, myocardial infarction, or vascular death; their relative safety was also assessed. The population studied comprised subgroups of patients with atherosclerotic vascular disease manifested as either recent ischaemic stroke, recent myocardial infarction, or symptomatic peripheral arterial disease. Patients were followed for 1 to 3 years. FINDINGS: 19,185 patients, with more than 6300 in each of the clinical subgroups, were recruited over 3 years, with a mean follow-up of 1.91 years. There were 1960 first events included in the outcome cluster on which an intention-to-treat analysis showed that patients treated with clopidogrel had an annual 5.32% risk of ischaemic stroke, myocardial infarction, or vascular death compared with 5.83% with aspirin. These rates reflect a statistically significant (p = 0.043) relative-risk reduction of 8.7% in favour of clopidogrel (95% Cl 0.3-16.5). Corresponding on-treatment analysis yielded a relative-risk reduction of 9.4%. There were no major differences in terms of safety. Reported adverse experiences in the clopidogrel and aspirin groups judged to be severe included rash (0.26% vs 0.10%), diarrhoea (0.23% vs 0.11%), upper gastrointestinal discomfort (0.97% vs 1.22%), intracranial haemorrhage (0.33% vs 0.47%), and gastrointestinal haemorrhage (0.52% vs 0.72%), respectively. There were ten (0.10%) patients in the clopidogrel group with significant reductions in neutrophils (< 1.2 x 10(9)/L) and 16 (0.17%) in the aspirin group. INTERPRETATION: Long-term administration of clopidogrel to patients with atherosclerotic vascular disease is more effective than aspirin in reducing the combined risk of ischaemic stroke, myocardial infarction, or vascular death. The overall safety profile of clopidogrel is at least as good as that of medium-dose aspirin