Horizontal movement data and accelerations collected from a single horn shark at Santa Catalina Island, California, USA

2 sources of data were collected from a single horn shark (Heterodontus francisci) at Santa Catalina Island, California, USA, over a period of 24 hours in June 2017: geopositional and acceleration data. Custom tag packages were externally attached to the dorsal fin of the shark that included an accelerometer data logger (Technosmart, AxyDepth) and an acoustic transmitter (Vemco V9 continuous pulse pinger, 2000 milliseconds). The shark was actively tracked from a tracking vessel above using a Vemco VR100 on-board receiver and VH110 directional hydrophone. During active tracking, geopositions were estimated for the tracking vessel relative to that of the tagged shark. Although boat position was recorded every 2 seconds, position data were filtered according to the closest possible estimations of the shark to the boat. Geopositional error for the shark was estimated to be 5 metres (via range tests at the study location). To characterise the shark's horizontal movements, we processed the geopositions into step lengths by calculating the Euclidean distances between consecutive geopositions. Acceleration data were recorded continuously at 25 hertz in 3 orthogonal dimensions, the dorso-ventral, anterior-posterior, and lateral axes. We summarised the acceleration signal across the 3 dimensions by calculating the overall dynamic body acceleration. The workspace contains 2 lists, entitled steps (containing the step lengths) and odbas (containing the accelerations)

Diel Vertical Habitat Use Observations of a Scalloped Hammerhead and a Bigeye Thresher in the Northern Gulf of Mexico

Understanding habitat use of elasmobranchs in pelagic environments is complicated due to the mobility of these large animals and their ability to move great distances in a three-dimensional environment. The Gulf of Mexico is a region where many highly migratory pelagic shark species occur, while in close proximity to coastal, anthropogenic activity including recreational and commercial fisheries. This study provides summary information on the vertical habitat use for a single male scalloped hammerhead and a single male bigeye thresher that were each caught and tagged with an archiving satellite tag. The scalloped hammerhead occupied shallow depths (<100 m) over the continental shelf during the 90 d deployment. The bigeye thresher exhibited strong patterns of diel vertical migrations by occupying depths below the thermocline (>350 m) during the day, then occupying shallower depths (50–100 m) during the night. By providing summary information, this note urges future research to provide scientific information on pelagic, highly migratory species for management efforts in the Gulf of Mexico region

Diel Vertical Habitat Use Observations of a Scalloped Hammerhead and a Bigeye Thresher in the Northern Gulf of Mexico

Understanding habitat use of elasmobranchs in pelagic environments is complicated due to the mobility of these large animals and their ability to move great distances in a three-dimensional environment. The Gulf of Mexico is a region where many highly migratory pelagic shark species occur, while in close proximity to coastal, anthropogenic activity including recreational and commercial fisheries. This study provides summary information on the vertical habitat use for a single male scalloped hammerhead and a single male bigeye thresher that were each caught and tagged with an archiving satellite tag. The scalloped hammerhead occupied shallow depths (350 m) during the day, then occupying shallower depths (50–100 m) during the night. By providing summary information, this note urges future research to provide scientific information on pelagic, highly migratory species for management efforts in the Gulf of Mexico region

Data from: Joint modelling of multi-scale animal movement data using hierarchical hidden Markov models

1. Hidden Markov models are prevalent in animal movement modelling, where they are widely used to infer behavioural modes and their drivers from various types of telemetry data. To allow for meaningful inference, observations need to be equally spaced in time, or otherwise regularly sampled, where the corresponding temporal resolution strongly affects what kind of behaviours can be inferred from the data. 2. Recent advances in biologging technology have led to a variety of novel telemetry sensors which often collect data from the same individual simultaneously at different time scales, e.g. step lengths obtained from GPS tags every hour, dive depths obtained from time-depth recorders once per dive, or accelerations obtained from accelerometers several times per second. However, to date, statistical machinery to address the corresponding complex multi-stream and multi-scale data is lacking. 3. We propose hierarchical hidden Markov models as a versatile statistical framework that naturally accounts for differing temporal resolutions across multiple variables. In these models, the observations are regarded as stemming from multiple, connected behavioural processes, each of which operates at the time scale at which the corresponding variables were observed. 4. By jointly modelling multiple data streams, collected at different temporal resolutions, corresponding models can be used to infer behavioural modes at multiple time scales, and in particular help to draw a much more comprehensive picture of an animal's movement patterns, e.g. with regard to long-term vs. short-term movement strategies. 5. The suggested approach is illustrated in two real-data applications, where we jointly model i) coarse-scale horizontal and fine-scale vertical Atlantic cod (Gadus morhua) movements throughout the English Channel, and ii) coarse-scale horizontal movements and corresponding fine-scale accelerations of a horn shark (Heterodontus francisci) tagged off the Californian coast

Padrões regionais do delta C-13 e delta N-15 para peixes comuns europeus (Sépia officinalis) em todo o Oceano Atlântico Nordeste e Mar Mediterrâneo

The European common cuttlefish, Sepia officinalis Linnaeus, 1758 is a coastal nektobenthic species ranging from the Shetland Islands through the Northeast Atlantic Ocean and Northwest Africa into the Mediterranean Sea [1]. This species constitutes one of the most economically valuable cephalopod resources in the Northeast Atlantic Ocean, supporting an important fishery resource [2,3]. Sepia officinalis has a relatively short lifespan of 1–2 years, early sexual maturity and an extended spawning season laying eggs on the seafloor with direct benthic, large hatchlings [4,5]. Given this species geographical distribution combined with limited dispersal, it has been a targeted model species to examine connectivity throughout the Northeast Atlantic Ocean and Mediterranean Sea (hereafter NEAO-MS) [6]. Natural biomarkers such as stable isotopes are commonly used to examine food web structure and ecosystem connectivity in marine environments [7,8]. Stable isotopes of carbon (δ13C) and nitrogen (δ15N) are particularly useful tracers due to their natural abundance being influenced by the environment and ease of measurement in body tissues without having to track individuals in a population. δ13C is traditionally used to trace carbon pathways because little fractionation occurs between predator and prey, and different primary producers (energy sources) often have unique δ13C values [9]. δ13C values of consumers are a product of the primary producers’ composition and influenced by the dissolved inorganic carbon (DIC) pool, as well as local abiotic factors including sea surface temperature, and can differ across ocean basins [10] and region-specific freshwater to marine gradients [9]. δ15N becomes enriched with increasing trophic level and is used to infer trophic position [7], but can also differ at the base of the food web. Depending upon the types of nutrients available to stimulate growth, δ15N values can be used to track energy flow in high-nutrient (nitrate) and low-nutrient (N2 fixation) ecosystems as well as new nitrogen (upwelled nitrate) versus regenerated nitrogen (ammonia, urea). Combining both δ13C and δ15N offers the potential to study the connectivity and population structure of species because longitudinal and latitudinal gradients exist throughout marine ecosystems [11,12], including the NEAO-MS [8,13].RTI2018-097908-B-I00, CEX2019-000928-Sinfo:eu-repo/semantics/publishedVersio

Regional patterns of delta C-13 and delta N-15 for European common cuttlefish (Sepia officinalis) throughout the Northeast Atlantic Ocean and Mediterranean Sea

Stable isotope compositions of carbon and nitrogen (expressed as delta C-13 and delta N-15) from the European common cuttlefish (Sepia officinalis) were measured in order to evaluate the utility of using these natural tracers throughout the Northeast Atlantic Ocean and Mediterranean Sea (NEAO-MS). Mantle tissue was obtained from S. officinalis collected from 11 sampling locations spanning a wide geographical coverage in the NEAO-MS. Significant differences of both delta C-13 and delta N-15 values were found among S. officinalis samples relative to sampling location. delta C-13 values did not show any discernable spatial trends; however, a distinct pattern of lower delta N-15 values in the Mediterranean Sea relative to the NEAO existed. Mean delta N-15 values of S. officinalis in the Mediterranean Sea averaged 2.5 parts per thousand low than conspecifics collected in the NEAO and showed a decreasing eastward trend within the Mediterranean Sea with the lowest values in the most eastern sampling locations. Results sugge delta N-15 may serve as a useful natural tracer for studies on the population structure of S. officinalis as, well as other marine organisms throughout the NEAO-MS