Conservation of migratory species exhibiting wide-ranging and multidimensional behaviors is challenged by management efforts that only utilize horizontal movements or produce static spatial-temporal ...products. For the deep-diving, critically endangered eastern Pacific leatherback turtle, tools that predict where turtles have high risks of fisheries interactions are urgently needed to prevent further population decline. We incorporated horizontal-vertical movement model results with spatial-temporal kernel density estimates and threat data (gear-specific fishing) to develop monthly maps of spatial risk. Specifically, we applied multistate hidden Markov models to a biotelemetry data set (n = 28 leatherback tracks, 2004-2007). Tracks with dive information were used to characterize turtle behavior as belonging to 1 of 3 states (transiting, residential with mixed diving, and residential with deep diving). Recent fishing effort data from Global Fishing Watch were integrated with predicted behaviors and monthly space-use estimates to create maps of relative risk of turtle-fisheries interactions. Drifting (pelagic) longline fishing gear had the highest average monthly fishing effort in the study region, and risk indices showed this gear to also have the greatest potential for high-risk interactions with turtles in a residential, deep-diving behavioral state. Monthly relative risk surfaces for all gears and behaviors were added to South Pacific TurtleWatch (SPTW) (https://www.upwell.org/sptw), a dynamic management tool for this leatherback population. These modifications will refine SPTW's capability to provide important predictions of potential high-risk bycatch areas for turtles undertaking specific behaviors. Our results demonstrate how multidimensional movement data, spatial-temporal density estimates, and threat data can be used to create a unique conservation tool. These methods serve as a framework for incorporating behavior into similar tools for other aquatic, aerial, and terrestrial taxa with multidimensional movement behaviors.
1. Management of highly migratory species is reliant on spatially and temporally explicit information on their distribution and abundance. Satellite telemetry provides time-series data on individual ...movements. However, these data are underutilized in management applications in part because they provide presence-only information rather than abundance information such as density. 2. Eastern North Pacific blue whales are listed as threatened, and ship strikes have been suggested as a key factor limiting their recovery. Here, we developed a satellite-telemetry-based habitat model in a case-control design for Eastern North Pacific blue whales Balaenoptera musculus that wa combined with previously published abundance estimates to predict habitat preference and densities. Further, we operationalize an automated, near-real-time whale density prediction tool based on up-to-date environmental data for use by managers and other stakeholders. 3. A switching state-space movement model was applied to 104 blue whale satellite tracks from 1994 to 2008 to account for errors in the location estimates and provide daily positions (case points). We simulated positions using a correlated random walk model (control points) and sampled the environment at each case and control point. Generalized additive mixed models and boosted regression trees were applied to determine the probability of occurrence based on environmental covariates. Models were used to predict 8-day and monthly resolution, year-round density estimates scaled by population abundance estimates that provide a critical tool for understanding seasonal and interannual changes in habitat use. 4. The telemetry-based habitat model predicted known blue whale hot spots and had seasonal agreement with sightings data, highlighting the skill of the model for predicting blue whale habitat preference and density. We identified high interannual variability in occurrence emphasizing the benefit of dynamic models compared to multiyear averages. 5. Synthesis and applications. This near-real-time tool allows a more accurate examination of the year-round spatio-temporal overlap of blue whales with potentially harmful human activities, such as shipping. This approach should also be applicable to other species for which sufficient telemetry data are available. The dynamic predictive product developed here is an important tool that allows managers to consider finer-scale management areas that are more economically feasible and socially acceptable.
Ceramide‐induced mitochondrial fission drives high‐fat diet (HFD)‐induced obesity. However, molecules targeting mitochondrial dynamics have shown limited benefits in murine obesity models. Here, we ...reveal that these compounds are either unable to block ceramide‐induced mitochondrial fission or require extended incubation periods to be effective. In contrast, targeting endolysosomal trafficking events important for mitochondrial fission rapidly and robustly prevented ceramide‐induced disruptions in mitochondrial form and function. By simultaneously inhibiting ARF6‐ and PIKfyve‐dependent trafficking events, the synthetic sphingolipid SH‐BC‐893 blocked palmitate‐ and ceramide‐induced mitochondrial fission, preserved mitochondrial function, and prevented ER stress in vitro. Similar benefits were observed in the tissues of HFD‐fed mice. Within 4 h of oral administration, SH‐BC‐893 normalized mitochondrial morphology in the livers and brains of HFD‐fed mice, improved mitochondrial function in white adipose tissue, and corrected aberrant plasma leptin and adiponectin levels. As an interventional agent, SH‐BC‐893 restored normal body weight, glucose disposal, and hepatic lipid levels in mice consuming a HFD. In sum, the sphingolipid analog SH‐BC‐893 robustly and acutely blocks ceramide‐induced mitochondrial dysfunction, correcting diet‐induced obesity and its metabolic sequelae.
SYNOPSIS
Ceramide‐induced mitochondrial fission drives diet‐induced obesity and its metabolic sequelae. Here, a small molecule targeting endocytic trafficking was found to block mitochondrial fission and reverse high fat diet‐induced obesity and metabolic dysfunction in mice.
The sphingolipid analog SH‐BC‐893 rapidly and robustly blocked ceramide‐induced mitochondrial fission by inhibiting ARF6‐dependent recycling and PIKfyve‐dependent lysosomal trafficking.
Within 4 h of oral administration, SH‐BC‐893 corrected mitochondrial morphology and/or dysfunction in the liver, brain, and white adipose tissue of mice with high fat diet‐induced obesity.
SH‐BC‐893 acutely re‐sensitized obese mice to leptin by reversing both hyperleptinemia and mitochondrial fragmentation in the hypothalamus, reducing food intake.
Intermittent oral dosing with SH‐BC‐893 was well tolerated and normalized body weight, improved glucose handling, and resolved hepatic steatosis despite continued consumption of a high fat diet.
Ceramide‐induced mitochondrial fission drives diet‐induced obesity and its metabolic sequelae. Here, a small molecule targeting endocytic trafficking was found to block mitochondrial fission and reverse high fat diet‐induced obesity and metabolic dysfunction in mice.
The cryptic 'lost years' of sea turtles challenge conservation efforts due to unknown movements and habitat utilisation of young life stages. Behavioural information strengthens dispersal and habitat ...utilisation models estimating unidentified movements. In this study, leatherback hatchlings were actively tracked with miniature acoustic tags off the east coast of Costa Rica for 83.15 min (± 9.12 SD) to determine their movements and swimming behaviour. Drifters were deployed throughout the tracking process to obtain surface current data. Hatchling (n = 42) over-ground and in-water swimming speed and bearing were calculated. Mean over-ground distance travelled was 2.03 km (± 0.71 km SD) with an over-ground average swim speed of 0.41 m/s (± 0.15 m/s SD). Mean bearing was 108.08° (± 20.19° SD) compared to the 137.56° (± 44.00° SD) bearing of nearshore ocean currents during tracking. Hatchling mean in-water swimming speed was 0.25 m/s (± 0.09 m/s SD). The lower in-water speed suggests hatchlings were advected by the currents, with overall movement strongly influenced by the current direction. This information can be assimilated into broader spatiotemporal distribution models to interpret the influence of directional swimming on ecosystem utilisation and help to achieve informed management decisions across all life stages of the population.
In oceans and seas worldwide, an increasing number of end-of-life anthropogenic offshore structures (e.g. platforms, pipelines, manifolds, windfarms, etc.) are facing full or partial removal. As part ...of the decommissioning process, studies on potential importance of subsea infrastructure to marine megafauna (defined as: cetaceans, pinnipeds, sirenians, large fish – such as sharks, rays, billfishes, and tuna, as well as marine reptiles, and seabirds) are lacking. Dedicated scientific Remotely Operated Vehicle (ROV) surveys around offshore installations are rare, but there is a wealth of archived industrial data and noteworthy species sightings posted publicly on various social media platforms. This study used routine, incidentally-collected ROV (n = 73) and commercial diver (n = 9) video recordings spanning 1998–2019 globally. Data were gathered directly from industrial partners (n = 36) and the public domain (YouTube; n = 46) to provide an account of marine megafauna presence and potential feeding behaviour in the near visible vicinity of subsea anthropogenic structures. A total of 79 video clips and 3 still images of marine megafauna near offshore structures were examined, resulting in 67 individual sightings and 16 sub-sightings (in which an individual was recorded within the same day). At least 178 individuals were identified to a minimum of 17 species of marine megafauna, amounting to a total (combined) sighting duration of 01:09:35 (hh:mm:ss). Results demonstrated proximate presence of marine megafauna (many of which are threatened species) to anthropogenic structures, with most animals displaying foraging or interaction behaviours with the structures. Observations included the deepest (2,779 m) confirmed record of a sleeper shark (Somniosus spp.) and the first confirmed visual evidence of seals following pipelines. These ROV observations demonstrate a latent source of easily-accessible information that can expand understanding of marine megafauna interactions with offshore anthropogenic infrastructure. Consequently, other workers in this field should be encouraged to re-analyse archived datasets, commence further collaborative research projects with industrial partners, and/or expand Internet search terms to additional species assemblages, in a bid to quantitatively elucidate relationships between offshore infrastructure and marine species.
Quantifying early life movements is essential to understanding migratory pathways and habitat use that can impact individuals’ success later in life. To gauge how neonatal movements set the stage for ...later habitat use, we tracked neonate leatherback turtles (n=94) with acoustic tags from Pacuare, Costa Rica, in 2016 and 2018. We analyzed movements using a first passage time analysis and random walk models, the results of which indicated neonates followed a fixed compass direction as they traveled away from shore and that strong currents in these areas resulted in advection. We combined the tracking data with concurrent environmental variables in a generalized additive mixed model framework. Our results showed the south-east current flow in this area has spatial and temporal structure that was not driven by the tidal current or local wind speed. Accounting for advection by the currents, in-water neonate swimming speed was significantly related to current speed, first passage time, and the year. Neonates had three main response strategies to currents above 0.5 m s-1, with most increasing their swimming speed and the rest maintaining either a constant or decreased swimming speed. Neonates were significantly larger in 2018 than in 2016 but their average swimming speed was not significantly related to body size, indicating that environmental factors were more important contributors to their dispersal. We conclude that abiotic factors, including the strength and direction of the currents, significantly affect the swimming and dispersal strategy of neonate leatherback turtles and these results can help to inform strategies for releases of neonate turtles from hatcheries, future tracking studies, and conservation efforts.
Species distribution models have been widely used in both terrestrial and marine systems, and applications have included invasive species management, evaluating potential effects of climate change, ...and conservation. Generally, only a single type of data can be accommodated within the model structures used, which may lead to higher uncertainty in the predictions when the data are sparse. In this case, it can be beneficial to pool data from multiple sources and data types, such as fishery observations and telemetry data. An integrated species distribution model (ISDM) utilizes data integration methods that address the challenges of harnessing multiple data types to estimate species distribution. In this study, an ISDM approach was developed to link turtle locations gathered as part of fishery observations with those derived from satellite telemetry in the East Pacific Ocean to enhance our understanding of a highly migratory and endangered marine species, the leatherback turtle (Dermochelys coriacea). These models were developed to support a dynamic management tool, South Pacific TurtleWatch, to identify high‐risk areas of management concern and help inform bycatch reduction efforts for this critically endangered species. This data fusion approach could be applied to other populations and species for which telemetry and other point source data are available.
The poorly understood movements of sea turtles during the ‘lost years’ of their early life history have been characterized as a ‘passive drifter’ stage. Biologging technology allows us to study ...patterns of dispersal, but the small body size of young life stages requires particular consideration that such tagging does not significantly impede animal movements. We tested the effect of instrument attachment methods for mobile acoustic tracking of hatchling sea turtles, including a design that would be suitable for leatherback turtles (Dermochelys coriacea). We obtained 8-week-old hatchery-reared green sea turtles (Chelonia mydas) (n = 12 individuals) and examined the effect of attaching Vemco V5 acoustic tags. Each animal’s swim speed, swimming depth, and stroke frequency were determined under three scenarios: control, direct Velcro® attachment to the carapace, and harness attachment, to determine if there was a significant difference amongst treatments. Turtle swimming speed was significantly slower during the middle period of the trial for the harness attachment compared with the control. No significant change in swim speed was observed when the tag was attached directly with Velcro®, and no significant change in dive depth was observed for either treatment compared to the control. Stroke frequency was significantly greater compared to the control at the end of the trial for the Velcro® attachment only, although there was no corresponding increase in swimming speed. This information can be used to design effective approaches for actively tracking free-ranging hatchling sea turtles to understand dispersal and survival of these vulnerable marine species.
The Eastern Pacific leatherback turtle population (Dermochelys coriacea) has declined precipitously in recent years. One of the major causes is bycatch from coastal and pelagic fisheries. Fisheries ...observations are often underutilized, despite strong potential for this data to affect policy. In this study, we created a spatiotemporal species distribution model that synthesizes fisheries observations with remotely sensed environmental data. The model will be developed into a dynamic management tool for the Eastern Pacific leatherback population. We obtained leatherback observation data from multiple fisheries that have operated in the Southeast Pacific (2001–2018). A dynamic Poisson point process model was applied to predict leatherback intensity (observation per unit area) as a function of dynamic environmental covariates. This model serves as a tool for application by managers and stakeholders toward the reduction of leatherback turtle bycatch and provides a modeling framework for analyzing fisheries observations from other vulnerable populations and species.
Through partnerships with multiple organizations, we were uniquely able to obtain and analyze fisheries‐derived observations to determine the spatiotemporal distribution of leatherback turtles within areas of high bycatch risk. We developed a species distribution modeling framework to analyze fisheries‐dependent observations that could be applied to other sources of point data and species of conservation concern. In view of the underutilized fisheries observations in policy development for protected species, this study is of direct and broad relevance to conservation policy and management.
The utilization and capabilities of biotelemetry are expanding enormously as technology and access rapidly improve. These large, correlated datasets pose statistical challenges requiring advanced ...statistical techniques to appropriately interpret and model animal movement. We used satellite telemetry data of critically endangered Eastern Pacific leatherback turtles (Dermochelys coriacea) to develop a habitat‐based model of their motility (and conversely residence time) using a hierarchical Bayesian framework, which could be broadly applied across species. To account for the spatiotemporally auto‐correlated, unbalanced, and presence‐only telemetry observations, in combination with dynamic environmental variables, a novel modeling approach was applied. We expanded a Poisson generalized linear model in a continuous‐time discrete‐space (CTDS) model framework to predict individual leatherback movement based on environmental drivers, such as sea surface temperature. Population‐level movement estimates were then obtained with a Bayesian approach and used to create monthly, near real‐time predictions of Eastern Pacific leatherback movement in the South Pacific Ocean. This model framework will inform the development of a dynamic ocean management model, “South Pacific TurtleWatch (SPTW),” and could be applied to telemetry data from other populations and species to predict motility and residence times in dynamic environments, while accounting for statistical uncertainties arising at multiple stages of telemetry analysis.
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