Rates of population differentiation and speciation are decoupled in sea snakes

Comparative phylogeography can inform many macroevolutionary questions, such as whether species diversification is limited by rates of geographical population differentiation. We examined the link between population genetic structure and species diversification in the fully aquatic sea snakes (Hydrophiinae) by comparing mitochondrial phylogeography across northern Australia in 16 species from two closely related clades that show contrasting diversification dynamics. Contrary to expectations from theory and several empirical studies, our results show that, at the geographical scale studied here, rates of population differentiation and speciation are not positively linked in sea snakes. The eight species sampled from the rapidly speciating Hydrophis clade have weak population differentiation that lacks geographical structure. By contrast, all eight sampled Aipysurus-Emydocephalus species show clear geographical patterns and many deep intraspecific splits, but have threefold slower speciation rates. Alternative factors, such as ecological specialization, species duration and geographical range size, may underlie rapid speciation in sea snakes.Charlotte R. Nitschke, Mathew Hourston, Vinay Udyawer and Kate L. Sander

Adapting the Marine Stewardship Council risk-based framework to estimate impacts on seabirds, marine mammals, marine turtles and sea snakes

This is the final version. Available from Elsevier via the DOI in this record. Information available on impacts of fisheries on target or bycatch species varies greatly, requiring development of risk assessment tools to determine potentially unacceptable levels. Seabirds, marine mammals, marine turtles and sea snakes are particularly vulnerable given their extreme life histories, and data are often lacking on their populations or bycatch rates with which to quantify fisheries impacts. The Marine Stewardship Council (MSC) use a semi-quantitative Productivity Susceptibility Analysis (PSA) that is applicable to all species, target and non-target, to calculate risk of impact and to provide a score for relevant Performance Indicators for fisheries undertaking certification. The most recent MSC Fisheries Standard Review provided an opportunity to test the appropriateness of using this tool and whether it was sufficiently precautionary for seabirds, marine mammals and reptiles . The existing PSA was tested on a range of species and fisheries and reviewed in relation to literature on these species groups. New taxa-specific PSAs were produced and then reviewed by taxa-specific experts and other relevant stakeholders (e.g., assessors, fisheries managers, non-governmental conservation organizations). The conclusions of the Fishery Standard Review process were that the new taxa-specific PSAs were more appropriate than the existing PSA for assessing fisheries risk for seabirds, marine mammals and reptiles, and that, as intended, they resulted in precautionary outcomes. The taxa-specific PSAs provide useful tools for true data-deficient fisheries to assess relative risk of impact. Where some data are available, the MSC could consider developing or adapting other approaches to support robust and relevant risk assessments.Marine Stewardship Counci

Quantifying dive behaviour and three-dimensional activity space of dugongs in the Gulf of Carpentaria

1 Introduction -- 2 Methods -- 2.1 Study Site -- 2.2 Depth of detection zones -- 2.3 Transmitter deployment and data collection -- 2.4 Data preparation and filtering -- 2.4.1 Location data -- 2.4.2 Depth data -- 2.4.3 Environmental data -- 2.5 Availability detection probability estimation -- 2.6 Three-dimensional activity space estimation and visualisation -- 3 Results -- 3.1 Availability detection probability -- 3.2 Three-dimensional activity space -- 4 Discussion -- 5 References -- 6 AppendicesMade available by via Publications (Legal Deposit) Act 2004 (NT)

Exploring habitat selection in sea snakes using passive acoustic monitoring and Bayesian hierarchical models

Resource selection studies often use analytical techniques that provide information at either a population or an individual level. We applied a Bayesian hierarchical model that simultaneously estimates population- and individual-level habitat selection to explore how varying levels of dietary specialisation affect resource requirements of 2 species of sea snakes that occupy the same coastal environment. We used passive acoustic telemetry to monitor the movements of the 2 species—a dietary generalist, Hydrophis (Lapemis) curtus, and a dietary specialist, H. elegans—and investigated how individuals select habitats based on habitat type, depth and proximity to sources of freshwater within a nearshore environment. Composition of diets in both species was also assessed using regurgitated material from captured individuals. Selection of habitats by the 2 species differed, with H. elegans displaying an affinity for mudflat and seagrass habitats <4 km from sources of freshwater and depths <3 m. H. curtus selected for slightly deeper seagrass habitats (1-4 m) further from freshwater sources (2-5 km). Data from regurgitated material showed that the diet of H. curtus comprised at least 4 families of fish and displayed some level of intraspecific predation, whereas H. elegans preyed solely on eels. Both species predominantly selected seagrass areas, indicating that these habitats provide key resources for sea snakes within nearshore environments. The results illustrated the utility of Bayesian hierarchical models when analysing passive acoustic monitoring data to provide population-level habitat selection metrics and incorporate individual-level variability in selection, both of which are necessary to inform targeted management and conservation practices

Using an acoustic telemetry array to assess fish volumetric space use: a case study on impoundments, hypoxia and an air-breathing species (Neoceratodus forsteri)

Facultative air-breathing fish can persist in hypoxic waters due to their capacity to acquire atmospheric oxygen. Most studies examining responses of air-breathing fish to aquatic hypoxia have occurred under experimental conditions. How air-breathing fish respond to hypoxic conditions in the field has received less attention. Using depth sensor transmitters and an array of acoustic receivers to monitor the facultative air-breathing Australian lungfish (Neoceratodus forsteri), we investigated habitat preferences and behavioural responses to seasonal hypoxic zones in a riverine impoundment. Three-dimensional (3-D) kernel utilisation distribution (KUD) models revealed that during stratified conditions, lungfish remained above the oxycline, rarely venturing into hypoxic waters, whereas during holomixis lungfish used a wider range of depths. Total volumetric space utilisation did not change significantly during stratified periods, but the distribution of space used changed, constrained by the oxycline. Despite N. forsteri having lungs to supplement oxygen requirements, the presence of a hypoxic zone constrained the core (50% 3-D-KUD) volumetric space used by lungfish t

Temporal and spatial activity-associated energy partitioning in free-swimming sea snakes

1. Partitioning energy between critical basal functions and activity-associated behaviours is aprimary determinant of animal survival. Consequently, habitat selection is likely to be drivenby the efficiency with which resources can be acquired from a heterogeneous energylandscape. 2. Determining how energy partitioning is achieved across temporal and spatial scales isparticularly challenging in aquatic animals due to the logistical limitations in estimating fieldmetabolic rates (FMR) while simultaneously examining habitat choice. 3. Here, accelerometry telemetry and bimodal respirometry were used to correlate vectorialdynamic body acceleration (VeDBA) with oxygen consumption rates ( 2) of sea snakes(Hydrophis curtus and H. elegans) across an ecologically-relevant temperature range.Subsequently, VeDBA of free-roaming snakes was used to estimate activity-associated FMRwithin a near-shore environment over diel, seasonal and spatial scales. 4. Diel changes in activity explained short-term patterns in FMR, whereas seasonal changes inwater temperature drove long-term patterns. Spatial analyses demonstrated that activity associatedFMR was elevated in productive seagrass and mudflat habitats, indicative of aconcentration of foraging efforts. 5. Our findings illustrate for the first time how sea snakes partition activity-associated FMRacross time and space, providing an approach by which we can monitor the impacts of, andvulnerabilities to, natural and anthropogenic disturbances like warming and trawl fisheries

The power of national acoustic tracking networks to assess the impacts of human activity on marine organisms during the COVID-19 pandemic

COVID-19 restrictions have led to an unprecedented global hiatus in anthropogenic activities, providing a unique opportunity to assess human impact on biological systems. Here, we describe how a national network of acoustic tracking receivers can be leveraged to assess the effects of human activity on animal movement and space use during such global disruptions. We outline variation in restrictions on human activity across Australian states and describe four mechanisms affecting human interactions with the marine environment: 1) reduction in economy and trade changing shipping traffic; 2) changes in export markets affecting commercial fisheries; 3) alterations in recreational activities; and 4) decline in tourism. We develop a roadmap for the analysis of acoustic tracking data across various scales using Australia’s national Integrated Marine Observing System (IMOS) Animal Tracking Facility as a case study. We illustrate the benefit of sustained observing systems and monitoring programs by assessing how a 51-day break in white shark (Carcharodon carcharias) cage-diving tourism due to COVID-19 restrictions affected the behaviour and space use of two resident species. This cessation of tourism activities represents the longest break since cage-diving vessels started day trips in this area in 2007. Long-term monitoring of the local environment reveals that the activity space of yellowtail kingfish (Seriola lalandi) was reduced when cage-diving boats were absent compared to periods following standard tourism operations. However, white shark residency and movements were not affected. Our roadmap is globally applicable and will assist researchers in designing studies to assess how anthropogenic activities can impact animal movement and distributions during regional, short-term through to major, unexpected disruptions like the COVID-19 pandemic

Continental-scale acoustic telemetry and network analysis reveal new insights into stock structure

Delineation of population structure (i.e. stocks) is crucial to successfully manage exploited species and to address conservation concerns for threatened species. Fish migration and associated movements are key mechanisms through which discrete populations mix and are thus important determinants of population structure. Detailed information on fish migration and movements is becoming more accessible through advances in telemetry and analysis methods however such information is not yet used systematically in stock structure assessment. Here, we described how detections of acoustically tagged fish across a continental-scale array of underwater acoustic receivers were used to assess stock structure and connectivity in seven teleost and seven shark species and compared to findings from genetic and conventional tagging. Network analysis revealed previously unknown population connections in some species, and in others bolstered support for existing stock discrimination by identifying nodes and routes important for connectivity. Species with less variability in their movements required smaller sample sizes (45–50 individuals) to reveal useful stock structure information. Our study shows the power of continental-scale acoustic telemetry networks to detect movements among fishery jurisdictions. We highlight methodological issues that need to be considered in the design of acoustic telemetry studies for investigating stock structure and the interpretation of the resulting data. The advent of broad-scale acoustic telemetry networks across the globe provides new avenues to understand how movement informs population structure and can lead to improved management