The recent introduction of low-cost, moored data-logging acoustic receivers has provided opportunities for tracking marine organisms over small (hundreds of metres) and large scales (hundreds of kilometres). Acoustic receivers have been deployed in many different environments to examine specific hypotheses regarding the movement of aquatic species. This technology provides many advantages for studying aquatic animal movement patterns, but also has limitations and provides unique difficulties for users. Study design, applications, advantages and limitations are discussed with examples from past and current studies. Data management and analysis techniques are in their infancy and few standardised techniques exist. Complications with data management and potential data analysis techniques are discussed. Examples from the literature are utilised wherever possible to provide useful references.

Effective ocean management and conservation of highly migratory species depends onresolving overlap between animal movements and distributions, and fishing effort.However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space-use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively), and were also associated with significant increases in fishing effort.We conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). Our results demonstrate an urgent need for conservation and management measures at high-seas hotspots of shark space use, and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real-time, dynamic management.Industrialised fishing is a major source of mortality for large marine animals (marine megafauna) 1-6 . Humans have hunted megafauna in the open ocean for at least 42,000 years 7 , but international fishing fleets targeting large, epipelagic fishes did not spread into the high seas (areas beyond national jurisdiction) until the 1950s 8 . Prior to this, the high seas constituted a spatial refuge largely free from exploitation as fishing pressure was concentrated on continental shelves 3,8 . Pelagic sharks are among the widest ranging vertebrates, with some species exhibiting annual ocean-basin-scale migrations 9 , long term trans-ocean movements 10 , and/or fine-scale site fidelity to preferred shelf and open ocean areas 5,9,11 . These behaviours could cause extensive spatial overlap with different fisheries from coastal areas to the deep ocean. On average, large pelagic sharks account for 52% of all identified shark catch worldwide in target fisheries or as bycatch 12 . Regional declines in abundance of pelagic sharks have been reported 13,14 , but it is unclear whether exposure to high fishing effort extends across ocean-wide population ranges and overlaps areas in the high seas where sharks are most abundant 5,13 .Conservation of pelagic sharkswhich currently have limited high seas management 12,15,16would benefit greatly from a clearer understanding of the spatial relationships between sharks' habitats and active fishing zones. However, obtaining unbiased estimates of shark and fisher distributions is complicated by the fact that most data on pelagic sharks come from catch records and other fishery-dependent sources 4,15,16 .Here, we provide the first global estimate of the extent of space use overlap of sharks with industrial fisheries. This is based on the analysis of the movements of pelagic sharks tagged with satellite transmitters in the Atlantic, Indian and Pacific oceans, together with fishing vessel movements m...

Human activities have substantially changed the world's oceans in recent decades, altering marine food webs, habitats and biogeochemical processes [1]. Cephalopods (squid, cuttlefish and octopuses) have a unique set of biological traits, including rapid growth, short lifespans and strong life-history plasticity, allowing them to adapt quickly to changing environmental conditions [2-4]. There has been growing speculation that cephalopod populations are proliferating in response to a changing environment, a perception fuelled by increasing trends in cephalopod fisheries catch [4,5]. To investigate long-term trends in cephalopod abundance, we assembled global time-series of cephalopod catch rates (catch per unit of fishing or sampling effort). We show that cephalopod populations have increased over the last six decades, a result that was remarkably consistent across a highly diverse set of cephalopod taxa. Positive trends were also evident for both fisheries-dependent and fisheries-independent time-series, suggesting that trends are not solely due to factors associated with developing fisheries. Our results suggest that large-scale, directional processes, common to a range of coastal and oceanic environments, are responsible. This study presents the first evidence that cephalopod populations have increased globally, indicating that these ecologically and commercially important invertebrates may have benefited from a changing ocean environment.

Acoustic telemetry has emerged as a leading approach to infer diel, tidal and lunar rhythmicity in the movements of aquatic organisms in a range of taxa. Typically, studies examine the relative frequency of detections from individuals tagged with acoustic transmitters, and then infer patterns in the species' behaviour, but studies to date have not controlled for factors that may influence tag detection patterns in the absence of animal behaviour. We compared patterns in acoustic detections from tagged cuttlefish Sepia apama and several fixed-location control tags, and used these data to highlight the danger of misinterpreting patterns in the absence of adequate controls. Cuttlefish and control tags displayed similar detection patterns, and correcting cuttlefish-detection data for the influence of environmental factors resulted in the opposite pattern of cuttlefish activity displayed prior to correction. This study highlights the danger of using acoustic data to infer animal behaviour in the absence of adequate controls.KEY WORDS: Acoustic telemetry · Rhythmicity · Behaviour · Diel · Activity · Temporal Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 419: [295][296][297][298][299][300][301] 2010 strongly influence detection frequency (e.g. wind speed, biological noise, current speeds; Heupel et al. 2006) typically occur with diel, tidal or lunar frequency, so it is likely that one may detect rhythmic patterns in detection frequency in the complete absence of tagged-animal behaviour. Consequently, using these types of analyses to create inferences about animal behaviour is justified only if the influence of alternative factors is discounted through the employment of controls. With the increasing frequency and scale of acoustic arrays deployed worldwide, the need to accurately interpret acoustic data has never been greater. Of the myriad of acoustic telemetry studies that use the relative frequency of detections to make inferences about animal behaviour, we could find no published studies that report the use of fixedlocation control tags to separate the patterns in detection frequency due to animal behaviour from those due to other (i.e. environmental) factors. Jackson et al. (2005) deployed a fixed-location reference tag to compare detection efficiency between different tagattachment methods (also with S. apama), but that study did not examine patterns in detection frequency through time.Here we examined the relationship between acoustic detections from tagged giant Australian cuttlefish Sepia apama and fixed-position control tags to show that patterns in detection frequency from animal tags are strongly influenced by factors other than animal behaviour. MATERIALS AND METHODSStudy site, species and tagging. Sepia apama (n = 7) were collected via SCUBA from breeding grounds at Point Lowly, South Australia (33°00' S, 137°44' E) during July of 2009 and tagged with Vemco acoustic transmitters (V9AP-2L, 69 kHz, 3.3 g in water, 46 mm length, mean delay 120 s...