Interactions between fur seals and a squid jig fishery in southern Australia

Interactions between Australian fur seals (Arctocephalus pusillus doriferus) and the Southern Squid Jig Fishery (SSJF) were investigated in April–May 2002. Details on the number of seals present, distance from the vessel, age and gender, and their behaviour were recorded using scan sampling techniques over 26 nights from eight vessels operating out of Portland and Port Fairy on the southwest coast of Victoria. Seals were observed on all nights but none were recorded in 30% of all (777) scan observations. Of the seals attending vessels at any one time (1.89 ± 0.24), 67% were involved in activities unrelated to jigging operations with the most common behaviour category being resting/grooming. Only 3.6% of observations involved seals targeting squid caught on jig lures whereas a further 29% were of foraging on squid within 40 m of the vessel. Damage to fishing gear attributable to seals was recorded on only three occasions. There was no evidence of negative impacts on seals from vessel operations. The majority of seals foraging on squid around vessels were adult females (71%) with the remainder being almost exclusively juvenile males. The current level of interactions between Australian fur seals and vessels in the SSJF appears minor.

A nanoscale SQUID operating at high magnetic fields

A washer-free Nb nanoSQUID has been developed for measuring magnetization changes from nanoscale objects. The SQUID loop is etched into a 250 nm wide Au/Nb bilayer track and the diameter of the SQUID hole is ~ 70 nm. In the presence of a magnetic field perpendicular to the plane of the SQUID, vortex penetration into the 250 nm wide track can be observed via the critical current–applied field characteristic and the value at which vortex first penetrates is consistent with the theoretical prediction. Upon removing the applied field, the penetrated vortices escape the track and the critical current at zero field is restored.

Visually guided eye growth in the squid

Summary Eyes with refractive error have reduced visual acuity and are rarely found in the wild. Vertebrate eyes possess a visually guided emmetropisation process within the retina which detects the sign of defocus, and regulates eye growth to align the retina at the focal plane of the eye's optical components to avoid the development of refractive error, such as myopia, an increasing problem in humans [1]. However, the vertebrate retina is complex, and it is not known which of the many classes of retinal neurons are involved [2]. We investigated whether the camera-type eye of an invertebrate, the squid, displays visually guided emmetropisation, despite squid eyes having a simple photoreceptor-only retina [3]. We exploited inherent longitudinal chromatic aberration (LCA) to create disparate focal lengths within squid eyes. We found that squid raised under orange light had proportionately longer eyes and more myopic refractions than those raised under blue light, and when switched between wavelengths, eye size and refractive status changed appropriately within a few days. This demonstrates that squid eye growth is visually guided, and suggests that the complex retina seen in vertebrates may not be required for emmetropisation.

Effect of proximity to the shelf edge on the diet of female Australian fur seals

The Australian fur seal Arctocephalus pusillus doriferus is a temperate latitude species with a breeding distribution restricted to Bass Strait, Australia. Recent studies of the foraging behaviour of female Australian fur seals indicated that they feed demersally in the shallow continental shelf waters, a behaviour that is in contrast to the epipelagic foraging of females of most other arctocephaline (Southern Hemisphere fur seals) species and akin to that observed in sea lions. These studies, however, were conducted at one colony (Kanowna Island) located in central northern Bass Strait, and it was suggested that the observed foraging behaviour may have been due to the distance of this colony from the continental shelf edge (180 km), making it inefficient to forage beyond it. Here, the diet of lactating Australian fur seals was compared between 2 colonies to test if differing proximity to the continental shelf edge resulted in differences in foraging behaviour. The 2 breeding colonies studied, Kanowna Island and The Skerries, were 180 and 25 km from the nearest shelf edge, respectively. We analysed a total of 917 scat samples collected at the 2 colonies between 1997 and 2001. From faecal analysis, 45 primarily demersal on-shelf species of fishes and cephalopods were identified. Only 4 species had a frequency of occurrence greater than 10%: redbait Emmelichthys nitidus, jack mackerel Trachurus sp., red rock cod Pseudophycis bachus, and Gould’s squid Nototodarus gouldi. No seasonal, annual or spatial differences were found between the 2 colonies, indicating that proximity to the shelf edge does not influence diet.

Attachment of magnetic molecules on a nanoSQUID

A novel procedure combining monolayer self-assembly with electron beam lithography has been developed for attaching ferritin nanoparticles to a submicron thin-film SQUID (superconducting quantum interference device). After opening a window in the PMMA (polymethylmethacrylate) resist, organic linker molecules are used to attach ferritin to the exposed parts of the gold overlayer of a Nb nanoSQUID. This allows the magnetic nanoparticles to be located optimally as far as magnetic coupling to the nanoSQUID is concerned.

Synthesis and growth of hematite nanodiscs through a facile hydrothermal approach

This study reports a facile hydrothermal method for the synthesis of monodispersed hematite (α-Fe2O3) nanodiscs under mild conditions. The method has features such as no use of surfactants, no toxic precursors, and no requirements of high-temperature decomposition of iron precursors in non-polar solvents. By this method, α-Fe2O3 nanodiscs were achieved with diameter of 50 ± 10 nm and thickness of ~6.5 nm by the hydrolysis of ferric chloride. The particle characteristics (e.g., shape, size, and distribution) and functional properties (e.g., magnetic and catalytic properties) were investigated by various advanced techniques, including TEM, AFM, XRD, BET, and SQUID. Such nanodiscs were proved to show unique magnetic properties, i.e., superparamagnetic property at a low temperature (e.g., 20 K) but ferromagnetic property at a room temperature (~300 K). They also exhibit low-temperature (<623 K) catalytic activity in CO oxidation because of extremely clean surfaces due to non-involvement of surfactants, compared with those spheres and ellipsoids capped by PVP molecules.

Stable isotopes reveal inter-annual and inter-individual variation in the diet of female Australian fur seals

Understanding the temporal and spatial variation of foraging habits of apex predators is central to understanding their role in marine ecosystems and how their populations may respond to environmental variability. In the present study, stable isotope analysis (C and N) of blood was used to investigate inter-individual and inter-annual differences in the diet of adult female Australian fur seals Arctocephalus pusillus doriferus. Positive correlations were observed between red cell and plasma values for δ¹³C and δ¹⁵N (r² = 0.47 and r² = 0.66, respectively, p < 0.001 in both cases), suggesting relatively consistent individual prey choices over 3 or 4 foraging trips. Mean δ¹⁵N values (12.8 to 17.5%) confirm the species occupies the highest marine trophic niche in the region. A significant decrease in plasma δ¹⁵N values, corresponding to two-thirds of a trophic level (ca. 2%), was observed between the 1998 to 2000 and 2003 to 2005 sampling periods. This was associated with a significant decrease in adult female body condition and is consistent with a decline, previously documented by faecal analysis, of the proportion of red cod Pseudophysis bachus, barracouta Thyrsites atun and Gould's squid Nototodarus gouldi in the diet and an increase in redbait Emmelichthys nitidus. While substantial variation in δ¹⁵N was observed within each age cohort, a significant decrease was observed with age, suggesting individual specialisation for particular prey types is evident early in adulthood, but that its composition changes as females age. In addition, generalized linear models indicated body mass had a negative influence on δ¹⁵N, which may reflect larger total body oxygen stores, facilitating individuals hunting cryptic prey of lower trophic level (e.g. octopus) on the sea floor.

Patterns of connectivity and population structure of the southern calamary Sepioteuthis australis in southern Australia

The southern calamary, Sepioteuthis australis, is a commercially and recreationally important inshore cephalopod endemic to southern Australia and New Zealand. Typical of other cephalopods, S. australis has a short life span, form nearshore spawning aggregations and undergo direct development. Such life history traits may restrict connectivity between spawning grounds creating highly structured and genetically differentiated populations that are susceptible to population crashes. Here we use seven polymorphic microsatellite markers to assess connectivity and population structure of S. australis across a large part of its geographic range in Australia. Little genetic differentiation was found between sampling locations. Overall, FST was low (0.005, 95% CI≤<0.001-0.011) and we detected no significant genetic differentiation between any of the locations sampled. There was no strong relationship between genetic and geographical distance, and our neighbour joining analysis did not show clustering of clades based on geographical locations. Similarly, network analysis showed strong connectivity amongst most locations, in particular, Tasmania appears to be well connected with several other locations and may act as an important source population. High levels of gene flow and connectivity between S. australis sampling sites across Australia are important for this short-lived species, ensuring resilience against spatial and temporal mortality fluctuations.

Temporal variation in the diet of gentoo penguins at the Falkland Islands

Knowledge of diet is critical in interpreting the ecological roles of marine top predators and provides information towards their conservation and management. The Falkland Islands hold the largest number of breeding gentoo penguins. Yet knowledge of gentoo penguin diet at the Falklands is limited to either broad taxonomic divisions of prey items or dietary samples collected only on a single day. This study is the first to investigate gentoo penguin diet at Cow Bay, Falklands, to the species level, over repeated sampling intervals during the breeding period. Through stomach content analysis, we determined diet over a large temporal scale (2002/2003/2004–2011/2012/2013) and between the guard and crèche periods of chick rearing. The principle prey item by reconstituted mass was rock cod fish Patagonotothen spp., for all periods (47–78 %) except that of the 2012/2013 crèche period (19 %) when Falkland herring Sprattus fugensis made up the bulk of the diet (52 %). Of the cephalopods recovered, Patagonian squid Doryteuthis gahi was prominent (1–24 %), while crustaceans contributed negligibly to gentoo penguin diet. Our findings revealed that gentoo penguins breeding at the Falkland Islands were primarily demersal foragers with an ability for pelagic feeding. Diet choice appears to reflect prey availability.