No abstract

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...

Environmental influences (temperature and oxygenation) on cod metabolism and their impact on the ecology of this species were investigated. Limiting oxygen concentration curves (O 2 level ranging between 15 and 100% air saturation) were established at 2, 5 and 10°C. The standard metabolic rate (SMR), the maximum metabolic rate and the metabolic scope were then modelled as functions of temperature and/or oxygen saturation. The mean SMR at 2, 5 and 10°C were 19.8±4.9, 30.8±6.1 and 54.3±4.1 mg O 2 h −1 kg −1 , respectively. Between 2 and 5°C, the active metabolic rate of cod almost doubled from 65 to 120 mg O 2 h −1 kg −1 , to reach 177 mg O 2 h −1 kg −1 at 10°C. In terms of metabolic scope (MS), the temperature rise from 2 to 5°C resulted in a twofold increase from 45 to 89 mg O 2 h −1 kg −1 , with MS reaching 123 mg O 2 h −1 kg −1 at 10°C. Our proposed model describing the impact of temperature and oxygen level provides new insight into the energetic interactions which govern the relationship between Atlantic cod and its environment. We reexamined published experimental and field studies from the angle of the regulation of metabolic power. We suggest that, when faced with heterogeneous or unstable hydrological conditions, cod tend to behaviourally maximise their metabolic scope. Through this adaptive response, fish reduce energy budgeting conflicts and presumably increase the probability of routinely operating away from lethal boundaries.

1986. The constraints on cephalopods: why squid aren't fish. Can. J. Zool. 64: 1591-1605.The convergent evolution of cephalopods and fish has often been discussed on an anatomical basis, but recent advances in the knowledge of cephalopod life cycles, physiology, and biochemistry suggest that there are constraints on cephalopods that prevent them from competing directly ,with fish. These advances are reviewed against the background of detailed information on fish from the perspective that the basic inefficiency of the jet-propulsion system has required bioenergetic, physiological, and biochemical adaptations in squid which maximize their metabolic rates. Such "high-energy" adaptations are suggested to have resulted in the short life history and semelparous reproductive patterns that seem to characterize these coleoid cephalopods. Conversely, the physiology and biochemistry of fish give them distinct advantages for long lives and iteroparity. O'DOR, R. K., et D. M. WEBBER. 1986. The constraints on cephalopods: why squid aren't fish. Can. J . Zool. 64: 1591 -1605 L'kvolution convergente des ~Cphalopodes et des poissons a souvent fait l'objet de discussions basCes sur I'anatomie des organismes, mais, plus rkcemment, l'acquisition de connaissances sur les cycles biologiques des ckphalopodes, leur physiologie et leur biochimie indique que des contraintes empkhent les ckphalopodes de faire une compktition directe aux poissons. Ces nouvelles donnCes sont rCvisCes a la lumi&re des donnCes disponibles sur les poissons en tenant compte que 17inefficacitC inhkrente au systkme de dkplacements par propulsion a oblige les ~Cphalopodes a dCvelopper des adaptations bioCnergCtiques, physiologiques et biochimiques propres a maximiser leur taux de mktabolisme. De telles adaptations a coot knergktique ClevC ont probablement donnk lieu au cycle biologique court et au mode de reproduction semelpare qui semble car?.ctkriser ces ~Cphalopodes colkoi'des. Inversement, la physiologie et la biochimie des poissons donnent lieu a une vie longue et un mode de reproduction itkropare.[Traduit par la revue]

Summary Acoustic telemetry is being increasingly used to study the ecology of many aquatic organisms. This widespread use has been advanced by national and international tracking programs that coordinate deployment of passive acoustic telemetry networks on a regional and continental scale to detect tagged animals. While it is well‐known that environmental conditions can affect the performance of acoustic receivers, these effects are rarely quantified despite the profound implications for tag detection and hence the ecological inferences. Here, we deployed eight receivers at different depths within the water column and at different orientations (hydrophone up or down) and 12 tags 200–800 m from the receivers for 234 days to investigate how the tag detection range of acoustic receivers varied through time and under different meteorologic and oceanographic conditions. The study showed that receiver depth and orientation, and time since deployment had the largest effect on the detection range. Thermocline gradient and depth, and wind speed were the environmental factors most affecting detection range, while wind direction, precipitation and atmospheric pressure had negligible or no effect. Comparison of results to a proposed general acoustic theory model and previous studies showed that findings from specific habitat types cannot be generalised and applied across other habitats or environments. A good understanding of the acoustic coverage and temporal variations in relation to environmental conditions are crucial to accurate interpretation of results, and ensuing management recommendations. We recommend that each study include stationary reference tags to measure changes in detection probability with time, help refine detection range, and be used to improve confidence in the reporting and interpretation of the data.