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

Continental-scale animal tracking reveals functional movement classes across marine taxa

Acoustic telemetry is a principle tool for observing aquatic animals, but coverage over large spatial scales remains a challenge. To resolve this, Australia has implemented the Integrated Marine Observing System’s Animal Tracking Facility which comprises a continental-scale hydrophone array and coordinated data repository. This national acoustic network connects localized projects, enabling simultaneous monitoring of multiple species over scales ranging from 100 s of meters to 1000 s of kilometers. There is a need to evaluate the utility of this national network in monitoring animal movement ecology, and to identify the spatial scales that the network effectively operates over. Cluster analyses assessed movements and residency of 2181 individuals from 92 species, and identified four functional movement classes apparent only through aggregating data across the entire national network. These functional movement classes described movement metrics of individuals rather than species, and highlighted the plasticity of movement patterns across and within populations and species. Network analyses assessed the utility and redundancy of each component of the national network, revealing multiple spatial scales of connectivity influenced by the geographic positioning of acoustic receivers. We demonstrate the significance of this nationally coordinated network of receivers to better reveal intra-specific differences in movement profiles and discuss implications for effective management

A trait-based framework for assessing the vulnerability of marine species to human impacts

Marine species and ecosystems are widely affected by anthropogenic stressors, ranging from pollution and fishing to climate change. Comprehensive assessments of how species and ecosystems are impacted by anthropogenic stressors are critical for guiding conservation and management investments. Previous global risk or vulnerability assessments have focused on marine habitats, or on limited taxa or specific regions. However, information about the susceptibility of marine species across a range of taxa to different stressors everywhere is required to predict how marine biodiversity will respond to human pressures. We present a novel framework that uses life-history traits to assess species' vulnerability to a stressor, which we compare across more than 44,000 species from 12 taxonomic groups (classes). Using expert elicitation and literature review, we assessed every combination of each of 42 traits and 22 anthropogenic stressors to calculate each species' or representative species group's sensitivity and adaptive capacity to stressors, and then used these assessments to derive their overall relative vulnerability. The stressors with the greatest potential impact were related to biomass removal (e.g., fisheries), pollution, and climate change. The taxa with the highest vulnerabilities across the range of stressors were mollusks, corals, and echinoderms, while elasmobranchs had the highest vulnerability to fishing-related stressors. Traits likely to confer vulnerability to climate change stressors were related to the presence of calcium carbonate structures, and whether a species exists across the interface of marine, terrestrial, and atmospheric realms. Traits likely to confer vulnerability to pollution stressors were related to planktonic state, organism size, and respiration. Such a replicable, broadly applicable method is useful for informing ocean conservation and management decisions at a range of scales, and the framework is amenable to further testing and improvement. Our framework for assessing the vulnerability of marine species is the first critical step toward generating cumulative human impact maps based on comprehensive assessments of species, rather than habitats

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