Crossing lines: a multidisciplinary framework for assessing connectivity of hammerhead sharks across jurisdictional boundaries

Conservation and management of migratory species can be complex and challenging. International agreements such as the Convention on Migratory Species (CMS) provide policy frameworks, but assessments and management can be hampered by lack of data and tractable mechanisms to integrate disparate datasets. An assessment of scalloped (Sphyrna lewini) and great (Sphyrna mokarran) hammerhead population structure and connectivity across northern Australia, Indonesia and Papua New Guinea (PNG) was conducted to inform management responses to CMS and Convention on International Trade in Endangered Species listings of these species. An Integrated Assessment Framework (IAF) was devised to systematically incorporate data across jurisdictions and create a regional synopsis, and amalgamated a suite of data from the Australasian region. Scalloped hammerhead populations are segregated by sex and size, with Australian populations dominated by juveniles and small adult males, while Indonesian and PNG populations included large adult females. The IAF process introduced genetic and tagging data to produce conceptual models of stock structure and movement. Several hypotheses were produced to explain stock structure and movement patterns, but more data are needed to identify the most likely hypothesis. This study demonstrates a process for assessing migratory species connectivity and highlights priority areas for hammerhead management and research

A standardisation framework for bio‐logging data to advance ecological research and conservation

Bio‐logging data obtained by tagging animals are key to addressing global conservation challenges. However, the many thousands of existing bio‐logging datasets are not easily discoverable, universally comparable, nor readily accessible through existing repositories and across platforms, slowing down ecological research and effective management. A set of universal standards is needed to ensure discoverability, interoperability and effective translation of bio‐logging data into research and management recommendations. We propose a standardisation framework adhering to existing data principles (FAIR: Findable, Accessible, Interoperable and Reusable; and TRUST: Transparency, Responsibility, User focus, Sustainability and Technology) and involving the use of simple templates to create a data flow from manufacturers and researchers to compliant repositories, where automated procedures should be in place to prepare data availability into four standardised levels: (a) decoded raw data, (b) curated data, (c) interpolated data and (d) gridded data. Our framework allows for integration of simple tabular arrays (e.g. csv files) and creation of sharable and interoperable network Common Data Form (netCDF) files containing all the needed information for accuracy‐of‐use, rightful attribution (ensuring data providers keep ownership through the entire process) and data preservation security. We show the standardisation benefits for all stakeholders involved, and illustrate the application of our framework by focusing on marine animals and by providing examples of the workflow across all data levels, including filled templates and code to process data between levels, as well as templates to prepare netCDF files ready for sharing. Adoption of our framework will facilitate collection of Essential Ocean Variables (EOVs) in support of the Global Ocean Observing System (GOOS) and inter‐governmental assessments (e.g. the World Ocean Assessment), and will provide a starting point for broader efforts to establish interoperable bio‐logging data formats across all fields in animal ecology

Long-term movement patterns of a coral reef predator

Long-term monitoring is required to fully define periodicity and patterns in animal movement. This is particularly relevant for defining what factors are driving the presence, location, and movements of individuals. The long-term movement and space use patterns of grey reef sharks, Carcharhinus amblyrhynchos, were examined on a whole of reef scale in the southern Great Barrier Reef to define whether movement and activity space varied through time. Twenty-nine C. amblyrhynchos were tracked for over 2 years to define movement patterns. All individuals showed high residency within the study site, but also had high roaming indices. This indicated that individuals remained in the region and used all of the monitored habitat (i.e., the entire reef perimeter). Use of space was consistent through time with high reuse of areas most of the year. Therefore, individuals maintained discrete home ranges, but undertook broader movements around the reef at times. Mature males showed greatest variation in movement with larger activity spaces and movement into new regions during the mating season (August-September). Depth use patterns also differed, suggesting behaviour or resource requirements varied between sexes. Examination of the long-term, reef-scale movements of C. amblyrhynchos has revealed that reproductive activity may play a key role in space use and activity patterns. It was unclear whether mating behaviour or an increased need for food to sustain reproductive activity and development played a greater role in these patterns. Reef shark movement patterns are becoming more clearly defined, but research is still required to fully understand the biological drivers for the observed patterns

Importance of environmental and biological drivers in the presence and space use of a reef-associated shark

As coral reef ecosystems come under increasing pressure from fisheries and climate change, understanding how species that rely on these habitats respond to changes within their environment is increasingly important. The presence and movement of 28 grey reef sharks Carcharhinus amblyrhynchos were monitored for 15 mo in the southern Great Barrier Reef in relation to environmental conditions and biological factors. Twenty-eight models including water temperature, atmospheric pressure, wind speed, rainfall and time (week or month), size and sex were tested against presence and activity space data and compared using Akaike information criterion (AIC). Model results for presence of individuals in relation to environmental conditions indicated that temperature and wind speed had weak effects, likely related to detectability. Models using 3 different measures of activity space indicated no relationship between shark activity space and environmental parameters. Week was a significant factor in the top performing activity space models, with males showing increased activity space during weeks in September, when mating is believed to occur. These results suggest changes in movement were biologically rather than environmentally driven. It appears that C. amblyrhynchos are adapted to a wide range of environmental conditions in coral reef habitats and that movement between or away from reef platforms is likely related to biological factors such as prey density, competition, reproduction or dispersal rather than environmental or seasonal changes

Using acoustic monitoring to evaluate MPAs for shark nursery areas: the importance of long-term data

The presence and movements of a population of young blacktip sharks (Carcharhinus limbatus) was monitored via a series of acoustic hydrophones over a period of three years to examine their use of a coastal nursery area. Data from this project were used to investigate the efficacy of hypothetical marine protected areas for this population. Small and large reserve designs were used to determine which would provide better protection for this population. The small reserve provided consistent levels of protection across years with sharks receiving good protection early in the summer season, but with declining protection thereafter. The large reserve provided less consistent levels of protection across years, but provided protection for a greater portion of time than the small reserve. Excursions from the small reserve were high early in the season and declined as sharks used this region less through the later portion of the summer. Excursions from the large reserve did not show any consistent pattern, but were also high early in the season and decreased through time as sharks used less of the reserve area. These results, coupled with previously calculated mortality estimates, revealed that the large reserve provided better protection for young sharks during their most vulnerable period within the nursery. We suggest that time-area closures for nursery populations of highly mobile shark species may be of value. Results of this study also show that long-term data may be critical to effective reserve design and placement, and assessment of reserve efficacy

Science or slaughter: need for lethal sampling of sharks

General consensus among scientists, commercial interests, and the public regarding the status of shark populations is leading to an increasing need for the scientific community to provide information to help guide effective management and conservation actions. Experience from other marine vertebrate taxa suggests that public, political, and media pressures will play an increasingly important part in setting research, management, and conservation priorities. We examined the potential implications of nonscientific influences on shark research. In particular,we considered whether lethal research sampling of sharks is justified. Although lethal sampling comes at a cost to a population, especially for threatened species, the conservation benefits from well-designed studies provide essential data that cannot be collected currently in any other way. Methods that enable nonlethal collection of life-history data on sharks are being developed (e.g., use of blood samples to detect maturity), but in the near future they will not provide widespread or significant benefits. Development of these techniques needs to continue, as does the way in which scientists coordinate their use of material collected during lethal sampling. For almost half of the known shark species there are insufficient data to determine their population status; thus, there is an ongoing need for further collection of scientific data to ensure all shark populations have a future. Shark populations will benefit most when decisions about the use of lethal sampling are made on the basis of scientific evidence that is free from individual, political, public, and media pressures

Importance of prey density in relation to the movement patterns of juvenile blacktip sharks (Carcharhinus limbatus) within a coastal nursery area

Previous research suggests that nursery areas provide an abundant food source as well as protection from predation for young sharks, and that these benefits are the reasons they use these areas. This study examined the abundance of prey species within a known nursery area, Terra Ceia Bay, Florida, and compared those data with the amount of time blacktip sharks spent within various geographic zones within the nursery. The most abundant prey species within the study site were pinfish, Lagodon rhomboides, pigfish, Orthopristis chrysoptera, spotfin mojarra, Eucinostomus argenteus, and silver perch, Bairdiella chrysoura. Prey species were found to be most abundant in the mid to southern portion of the nursery area, whereas sharks spent the majority of their time within the northern portion of the study site. There was no correlation between the amount of time sharks (as a whole and by individual) spent within a geographic zone and the abundance of prey species within that area. These results suggest that prey abundance is not the main factor directing the movement patterns and habitat choice of juvenile Carcharhinus limbatus within Terra Ceia Bay. Predator avoidance may be more important in the use of the nursery grounds by these young animals than prey abundance

Habitat and space use of an abundant nearshore shark, Rhizoprionodon taylori

Shark resource-use strategies affect how they will respond to changes within their environment and, as such, may be important to consider in conservation and management. Movement data on sharks that use nearshore areas is particularly valuable because these habitats are highly dynamic. The present study used passive acoustic telemetry to examine the space-use, habitat-selection and habitat-specialisation patterns of the Australian sharpnose shark, Rhizoprionodon taylori, in a nearshore area. Habitat selectivity and specialisation were assessed across five benthic habitat types, including outer bay, seagrass, reef, sandy inshore and intertidal mudflats. The majority of R. taylori sharks were present for short periods of time, ranging from 1 to 112 days (mean ± s.e. = 16.9 ± 4.9). Activity-space analysis indicated that R. taylori roamed widely, but monthly activity-space size was consistent among individuals and through time. Both the population and individuals displayed wide habitat niches, indicating that the species may be resilient to environmental change. However, R. taylori consistently selected for seagrass over other habitats, potentially for feeding. Therefore, declines in seagrass availability may reduce R. taylori presence in nearshore areas and may be relevant to spatial management of this species

Depth and space use of leopard coralgrouper Plectropomus leopardus using passive acoustic tracking

Understanding fish movements can help define the seasonal importance of different habitats and isolate spatial and temporal vulnerability to exploitation. Leopard coralgrouper Plectropomus leopardus is one of the main targeted fishery species in the Great Barrier Reef; however, there is no information on long-term movement patterns based on continuous and frequent data points. The objective of this study was to determine long-term space use of P. leopardus and identify any seasonal variation in movement trends. A total of 124 P. leopardus were implanted with V13P acoustic transmitters between 2010 and 2012 and passively tracked. Forty-five VR2W receivers were deployed at 2 reefs to track the movements of tagged individuals. The influence of time of day, season, tagging year, location, and water temperature on several movement measures was investigated. Of the 124 fish tagged, 74 individuals had sufficient detections to be included in analysis of horizontal movement, and 55 were used to analyse vertical movements. Results showed increased horizontal movements and higher activity in deeper water during the day in the austral summer. Movement patterns, both vertically and horizontally, appeared to be influenced by water temperature, but also corresponded with spawning season. Despite increased movements during summer, individuals typically remained in a small area ~0.5 km2 throughout detection periods, indicating that long-range spawning-related movements are rare and that adequate resources are obtained within a small section of habitat year-round. This study provides long-term (~3 yr) movement data for an economically significant reef fish and increases knowledge of spatial and temporal space use patterns

Running before the storm: blacktip sharks respond to falling barometric pressure associated with Tropical Storm Gabrielle

A small population of juvenile (<1 year old) blacktip sharks Carcharhinus limbatus responded to the approach of a tropical storm by moving to deeper water. Examination of meterological variables suggested that the movement of the blacktip sharks was triggered by a drop in barometric pressure associated with the approach of the storm. This response was consistent for all the fish being studied, and all blacktip sharks returned to the shallow nursery area after the storm's passage, suggesting that this was an innate behaviour