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Inferences regarding animal presence from passive acoustic receiver arrays are driven by the spatial configuration of receivers. Large, dense arrays provide more information, but maintenance of multiple receivers is costly. Configuring acoustic receiver arrays to maximise coverage while minimising cost is therefore paramount. This study used data from a dense acoustic receiver array within a white shark Carcharodon carcharias nursery area on the east coast of Australia to assess how detection data of tagged white sharks in the area was affected by reducing the array size. Receivers were sub-sampled post hoc by simple random sampling, clustered random sampling, and sampling of the top performing receivers. Using the top performing receivers, array size could be reduced by 60% (10 out of 25 receivers) while still detecting a median of 100% of white sharks detected with the full array. With random and clustered sampling methods, a 40% reduction in array size (15 out of 25 receivers) detected a median of 100% of sharks. Reducing the array size by 60% using the top performing receivers resulted in a 35% decrease in the median number of detections per visit of the tagged sharks (67 out of 102.5 detections). In comparison, reducing the array by the same amount with random and clustered sampling methods resulted in a 57% decrease (44 out of 102.5 detections). The post hoc sampling methods used in this study are an empirical approach for optimising placement of limited receiver resources with broad application for establishing cost-effective monitoring.

In comparison to other behaviours, large predators expend relatively large amounts of energy foraging for prey, based on expected high return. Documenting how they manage costs and benefits of feeding is difficult, particularly for marine predators. In July and August of 2004 and 2005, we combined animal-borne video, accelerometry and depth sensors to examine the underwater behaviour during white shark (Carcharodon carcharias) breaching at Seal Island, South Africa (34.1373°S, 18.5825°E)—where sharks launch from the water while attacking Cape fur seals (Arctocephalus pusillus pusillus). We show that breaching begins at depths up to 20 m, is characterised by a brief (~ 7 to 16 s) ascent to the surface during which pitch angle increases by ~ 30° and both tail-beat frequency and swim speed (determined using biomechanical principles) increase by a maximum of 6.5-fold (0.39–2.50 Hz and 1.0–6.5 m s−1, respectively). Sharks also demonstrated the ability to rapidly adjust their approach to the seal during ascent. Dominant tail-beat frequency during breaching was 2.1–4.2 times higher (0.83–1.67 Hz) than during non-predatory ascents (0.4 Hz), suggestive of the large increase in power required to breach. Examination of foraging behaviour through biologger deployments may play an increasingly important role in predicting the resource requirements of large predators and developing appropriate conservation measures, as their populations are generally under threat world-wide.

In broadcast spawners, low densities and poor spawning synchronization can reduce fertilization success. In wild populations, individuals in close proximity tend to spawn more synchronously than those further apart, sug- gesting that low spawner densities may reduce gamete pro- duction by lessening the efficacy of pheromone signalling. This study assessed the role of adult density in aggregation patterns and spawning synchronization in a semi-sessile, hermaphroditic scallop, Pecten fumatus. The study was carried out in Great Bay, Tasmania, Australia (147.335 W, 43.220 S) in 2010-2012 by assessing (1) the relationship between density, small-scale aggregation patterns and near- est neighbour distance (NND), (2) the temporal pattern of spawning synchronization, and (3) the effect of site density and conspecific proximity on the probability of spawn- ing. Densities observed in the field ranged from 1.455 to 0.021 ind m −2 . Sites with lower densities had less small- scale aggregation and greater NNDs. Patterns of small- scale aggregation and NNDs in P. fumatus were compara- ble to those observed in a gonochoristic species. Spawning synchronization was highly variable, ranging between 3.5

Stable isotope analysis is increasingly used in ecological studies. Because lipid content influences δ13C, lipids should be removed from lipid-rich samples before δ13C analysis. To account for differences in δ13C arising from differences in lipid content, relationships between lipid content, C:N ratio and Δδ13C with lipid removal can be used to normalise lipid content to uniform levels. We investigate these relationships for salmonid muscle and evaluate the suitability of previously published normalisation equations for these fish. Salmonids with a wide range of condition (muscle lipid content = 3–35% of dry weight) were considered. There were no consistent relationships between lipid content or C:N ratio and Δδ15N. There were linear relationships between C:N ratio and lipid content (L = −16.53 + 6.27 × C:N); C:N ratio and Δδ13C (Δδ13C = −1.87 + 0.65 × C:N); and lipid content and Δδ13C (Δδ13C = 0.01 + 0.10 × L), which should be used on salmonid stable isotope studies.

Age-specific information on individual octopus reproductive development and investment from wild populations has until recently been unobtainable. Using daily-formed increments within stylets (internal shells) the individual ages of 503 wild Octopus pallidus were determined. In addition, detailed reproductive information was collected for each of the aged octopus, along with reproductive data for an additional 925 octopus. All of the octopus were collected from Bass Strait waters in south-eastern Australia from November 2004 to November 2006. This information was used to investigate seasonal trends in reproductive scheduling and investment, fecundity and egg size. Maturation in O. pallidus primarily depends on size with little relationship to age and is highly variable between genders, with females >350 days still maturing in comparison to all males >142 days being mature. Size at 50% maturity for females was approximately 473 g, which is considerably larger than male 100% maturity at

Most marine invertebrates experience variable environments and for broadcast spawners, fertilisation success increases with greater synchronisation of spawning, so a capital breeding strategy is predicted. However, this prediction should be tested for species with protracted breeding seasons, since it is not clear how reproduction is fuelled over several consecutive months of spawning. The simultaneous hermaphrodite scallop Pecten fumatus was used to test the hypothesis that protracted spawning is supported by both capital and income strategies, depending on the state of energy reserves and food availability at the time of oocyte maturation. The study was carried out in Great Bay, Tasmania, Australia (147.335W, 43.220S) in 2010/2011. The use of glycogen, protein and lipid in the muscle, gonad, and digestive gland was examined, along with the role of atretic eggs as an alternative energy source for oogenesis and maturation. The reproductive stage of an individual was determined using only the ovaries. P. fumatus uses a capital breeding strategy early in the reproductive cycle during winter and spring (August–October) with muscle glycogen and protein and digestive gland lipid providing energy for oogenesis. Given there was no evidence of energy stores being used later in the reproductive cycle in late spring and summer (November–March), when less food was available for direct fuelling of reproduction, it appears that metabolites produced from oocyte lysis may have fuelled oogenesis. Recycling of energy from oocyte resorption must be considered as part of the strategy of energy use to fuel reproduction in marine invertebrates.

Temperature is known to have a strong influence on cephalopod growth during the early exponential growth phase. Most captive growth studies have used constant temperature regimes and assumed that populations are composed of identically sized individuals at hatching, overlooking the effects of seasonal temperature variation and individual hatchling size heterogeneity. This study investigated the relative roles of initial hatchling size and simulated natural seasonal temperature regimes on the growth of 64 captive Octopus pallidus over a 4-month period. Initial weights were recorded, and daily food consumption and fortnightly growth monitored. Two temperature treatments were applied replicating local seasonal water temperatures: spring/summer (14–18°C) and summer/autumn (18–14°C). Overall octopuses in the spring/summer treatment grew at a rate of 1.42% bwd−1 (% body weight per day) compared to 1.72% bwd−1 in the summer/autumn treatment. Initial size influenced growth rate in the summer/autumn treatment with smaller octopuses (

The cost of reproduction for the terminal spawning onychoteuthid squid, Moroteuthis ingens, was analysed using measures of condition and tissue biochemistry. Both males and females showed a dramatic drop in the weight of the gonad in stage 6 (spent) individuals. The mantle weight and nidamental gland weight of females also decreased during the maturation process. Males, however, had a marked increase in both the penis and spermatophoric complex weight in spent individuals, while female oviducal gland weight and nidamental gland length also increased in stage 6 individuals. Residual analysis indicated that testis growth was not developing at the expense of mantle growth, although there was a suggestion of cost to the fins. Females showed that the development of the ovary occurred at a cost to both the mantle and fins. Overall body condition also declined with maturity stage for both males and females, with stage 6 individuals of both sexes in poor condition. Very few females had eggs in the oviducts, suggesting that the oviducts are used as ducts instead of storage organs. Proximal analysis revealed a loss of constituents within the mantle during maturation, with an associated increase in water, indicating the remobilization of energy from the mantle to fuel reproduction. This study suggests that the digestive gland is not used as an energy store in this species.