Ocean Tracking Network

Upstream fish movement in the Danube River at the Iron Gate is blocked by the massive hydropower dams and ship locks, as shown by tracking six fish species (vimba bream Vimba vimba, common nase Chondrostoma nasus, barbel Barbus barbus, asp Leuciscus aspius, Pontic shad Alosa immaculata and common carp Cyprinus carpio). In the absence of effective fish passage systems, the current level of river connectivity is insufficient to support upstream movement and migration for this diverse, multispecies fish community. The tagged cyprinids displayed evidence of migratory behaviour. Individuals of vimba bream, barbel, asp and common nase that were transported across the lowermost dam and released into the lower reservoir section showed rapid upstream movement, suggesting that the reservoir itself did not present significant obstacles to migration. Some covered the entire 76-km long reservoir within a few days to 2 weeks but were ultimately blocked by the next dam. Cyprinids released below the dams were recorded at varying depths and on both sides of the river. Asp, barbel, common nase and vimba bream moved both upstream and downstream relatively close to the surface below the Iron Gate II dam, averaging 2-3 m below the surface, but also diving down to about 10-20 m. Future studies combining three-dimensional telemetry methods and detailed information on hydrology below the dams could provide further information on the behaviours of the different fish species, which is needed to design efficient fish passage solutions.

ABSTRACT Objective Alewives Alosa pseudoharengus are a culturally, ecologically, and economically important anadromous fish in the northwest Atlantic, yet their movement ecology remains poorly understood. This study was designed to examine mortality events and movement patterns of Alewives, including diel vertical migrations. Methods Using acoustic telemetry, we tagged 32 Alewives during their postspawning migrations through Passamaquoddy Bay (New Brunswick, Canada, and Maine, USA) toward the Bay of Fundy. Generalized additive models (GAMs) were used to examine the spatial distribution and timing of Alewife migrations through the bay. We also used GAMs to investigate occurrences of diel vertical migration in relation to tidal levels. Results Six of the tagged Alewives died during the study, with most mortalities occurring earlier in their migration within the river and estuary habitats, including four cases of endothermic predation: three in the estuary and one in the inner bay. Alewives were predicted to occupy three distinct spatial hot spots over time: the river and estuary during weeks 25–27, the inner bay during weeks 28–30, and the outer bay during weeks 31–32. Regardless of tidal height, the GAMs predicted that Alewives were deeper in the water column during the day (1200–2000 hours) and shallower at night (0200–0700 hours), with intermediate periods used to transition between these depths, indicating that Alewives undertook diel vertical migrations in the marine environment. Conclusions As Alewife populations continue to decline, this research highlights critical aspects of their postspawning movement ecology and underscores the importance of binational and multijurisdictional cooperation in the effective management of this species.

ABSTRACTThe role of pathogens in impacting the behaviour and fate of salmonids has been studied extensively for some selected pathogens such as sea lice. However, the whole pathobiome of the fish are seldom considered and may confound and influence the study species in situ. In this study, we investigated the presence of pathogens in returning adult wild and hatchery salmon in the river Vosso using gill samples analysed in high‐throughput PCR with a selection of assays targeting different fish pathogens. In addition, the samples were analysed for gene expressions that have been previously linked to imminent mortality, thermal stress, and inflammation related biomarkers. These data were linked to the behaviour of the individual fish collected from acoustic telemetry tags inserted in the abdomen of the fish. Previous analyses have suggested that the behaviour of the hatchery and wild salmon in this study area is different; however, there was no evidence that the pathobiome or the gene expression of the two groups of salmon (39 wild and 14 hatchery) could explain the behavioural differences between these two groups. Furthermore, neither pathogen profile nor gene expressions had a significant relationship between metrics of behaviour or survival of the fish. Results suggest that gene expression and pathogen screenings are insufficient to predict fates of migrating salmon. The Vosso salmon is a threatened population in Norway after collapsing in the 1980s; these data contribute to ongoing efforts to identify factors that are limiting the recovery of this population after decades of poor returns.

This candid perspective written by scholars from diverse disciplinary backgrounds is intended to advance conversations about the realities of peer review and its inherent limitations. Trust in a process or institution is built slowly and can be destroyed quickly. Trust in the peer review process for scholarly outputs (i.e., journal articles) is being eroded by high-profile scandals, exaggerated news stories, exposés, corrections, retractions, and anecdotes about poor practices. Diminished trust in the peer review process has real-world consequences and threatens the uptake of critical scientific advances. The literature on “crises of trust” tells us that rebuilding diminished trust takes time and requires frank admission and discussion of problems, creative thinking that addresses rather than dismisses criticisms, and planning and enacting short- and long-term reforms to address the root causes of problems. This article takes steps in this direction by presenting eight peer review reality checks and summarizing efforts to address their weaknesses using a harm reduction approach, though we recognize that reforms take time and some problems may never be fully rectified. While some forms of harm reduction will require structural and procedural changes, we emphasize the vital role that training editors, reviewers, and authors has in harm reduction. Additionally, consumers of science need training about how the peer review process works and how to critically evaluate research findings. No amount of self-policing, transparency, or reform to peer review will eliminate all bad actors, unscrupulous publishers, perverse incentives that reward cutting corners, intentional deception, or bias. However, the scientific community can act to minimize the harms from these activities, while simultaneously (re)building the peer review process. A peer review system is needed, even if it is imperfect.

Understanding the causal relationships that contribute to mortality in populations is a priority for epidemiology, animal husbandry and ecology. Of all the sources of mortality in nature, predation is perhaps the most important, while simultaneously being one of the most difficult to study and understand. In this opinion piece, we use the epidemiological concept of the sufficient-component cause model to outline why we believe that predation studies often misrepresent predators as sufficient cause of death (or natural mortality) in ecological studies. This is pivotal in conservation biology because such studies have often led to demands for predator removal throughout the world. We use the sufficient-component cause model to illustrate the paradox that multiple studies, each studying singular putative causes of mortality (including predation), will sum to more than 100% mortality when added together. We suggest that the sufficient-component framework should be integrated into both fundamental and applied ecology to better understand the role of predators in natural ecosystems.

Abstract 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.

The sea trout (anadromous brown troutSalmo trutta) displays extensive among-individual variation in marine migration behaviour. We studied the migration behaviour of 286 sea trout (27-89 cm) tagged with acoustic transmitters in the spring, in 7 populations located in 2 distinct marine fjord systems in Norway. We examined whether individual nutritional state, sex and body size influenced marine migration behaviour in terms of (1) the decision to migrate to the sea or remain resident in freshwater and/or estuarine habitats, (2) seasonal timing of sea entry, (3) duration of the marine residency and (4) migration distance at sea from the home river. Most sea trout were in a poor nutritional state in the spring prior to migration. Sea trout with low body condition factors and low plasma triglyceride levels were more likely to migrate to sea, and low triglyceride levels were also associated with earlier sea entry. Poor body condition also increased the probability of individuals remaining at sea longer and migrating further offshore compared to fish in better condition. Females were more likely to migrate to the sea than males. Larger fish were also more likely to migrate to the sea instead of remaining in freshwater and estuaries, and dispersed over greater distances from the river than smaller fish. In conclusion, this study documented general trends across multiple populations and showed that nutritional state, sex and body size influence important aspects of the marine migration behaviour of sea trout.

We investigated the response of Atlantic salmon (Salmo salar) to capture and handling stressors by analyzing fine-scale locomotor activity using accelerometer data loggers and broader-scale movements by tracking migration with radiotelemetry. Half the sample population was exposed to experimental exercise and air exposure and released with a control group to simulate fisheries handling. All but two of the surviving fish (both in the treatment group) returned to the counting fence to resume the 2016 spawning migration (survival = 86%–91%). There were no differences in postrelease locomotor activity, measured by an index of total body action (jerk), between control and treatment salmon (p = 0.81). Comparison of mean time to return to the counting fence against a null model revealed that treatment salmon were significantly delayed in returning to the counting fence (p < 0.01), whereas control fish were not (p = 0.24). Both the abiotic environment and human interactions influenced locomotor activity of the migratory fish and synchrony of the migration with untreated conspecifics.

Animal telemetry is a powerful tool for observing marine animals and the physical environments that they inhabit, from coastal and continental shelf ecosystems to polar seas and open oceans. Satellite-linked biologgers and networks of acoustic receivers allow animals to be reliably monitored over scales of tens of meters to thousands of kilometers, giving insight into their habitat use, home range size, the phenology of migratory patterns and the biotic and abiotic factors that drive their distributions. Furthermore, physical environmental variables can be collected using animals as autonomous sampling platforms, increasing spatial and temporal coverage of global oceanographic observation systems. The use of animal telemetry, therefore, has the capacity to provide measures from a suite of essential ocean variables (EOVs) for improved monitoring of Earth's oceans. Here we outline the design features of animal telemetry systems, describe current applications and their benefits and challenges, and discuss future directions. We describe new analytical techniques that improve our ability to not only quantify animal movements but to also provide a powerful framework for comparative studies across taxa. We discuss the application of animal telemetry and its capacity to collect biotic and abiotic data, how the data collected can be incorporated into ocean observing systems, and the role these data can play in improved ocean management.