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- Multidisciplinary estimates of connectivity and population structure suggest the use of multiple units for the conservation and management of meagre, Argyrosomus regiusPublication . Abecasis, David; Ogden, R.; Winkler, Alexander; Gandra, Miguel; Khallahi, B.; Diallo, M.; Cabrera-Castro, R.; Weiller, Y.; Erzini, Karim; Afonso, P.; Assis, JorgeInformation on population structure and connectivity of targeted species is key for proper implementation of spatial conservation measures. We used a combination of genomics, biophysical modelling, and biotelemetry to infer the population structure and connectivity of Atlantic meagre, an important fisheries resource throughout its distribution. Genetic samples from previously identified Atlantic spawning locations (Gironde, Tejo, Guadalquivir, Banc d'Arguin) and two additional regions (Algarve and Senegal) were analysed using genome-wide SNP-genotyping and mitochondrial DNA analyses. Biophysical models were conducted to investigate larval dispersal and connectivity from the known Atlantic spawning locations. Additionally, thirteen fish were double-tagged with biotelemetry transmitters off the Algarve (Portugal) to assess movement patterns and connectivity of adult individuals. This multidisciplinary approach provided a robust overview of meagre population structure and connectivity in the Atlantic. Nuclear SNP-genotyping showed a clear differentiation between the European and African populations, with significant isolation of the few known Atlantic spawning sites. The limited level of connectivity between these subpopulations is potentially driven by adults, capable of wide-ranging movements and connecting sites 500 km apart, as evidenced by tagging studies, whilst larval dispersal inferred by modelling is much more limited (average of 52 km; 95% of connectivity events up to 174 km). Our results show sufficient evidence of population structure, particularly between Africa and Europe but also within Europe, for the meagre to be managed as separate stocks. Additionally, considering the low degree of larvae connectivity, the implementation of marine protected areas in key spawning sites could be crucial towards species sustainability.
- Residency and space use estimation methods based on passive acoustic telemetry dataPublication . Kraft, Sebastian; Gandra, Miguel; Lennox, R. J.; Mourier, J.; Winkler, Alexander; Abecasis, DavidAcoustic telemetry has helped overcome many of the challenges faced when studying the movement ecology of aquatic species, allowing to obtain unprecedented amounts of data. This has made it into one of the most widely used methods nowadays. Many ways to analyse acoustic telemetry data have been made available and deciding on how to analyse the data requires considering the type of research objectives, relevant properties of the data (e.g., resolution, study design, equipment), habits of the study species, researcher experience, among others. To ease this decision process, here we showcase (1) some of the methods used to estimate pseudo-positions and positions from raw acoustic telemetry data, (2) methods to estimate residency and (3) methods to estimate two-dimensional home and occurrence range using geometric or hull-based methods and density-distribution methods, a network-based approach, and three-dimensional methods. We provide examples of some of these were tested using a sample of real data. With this we intend to provide the necessary background for the selection of the method(s) that better fit specific research objectives when using acoustic telemetry.
- Assessment of fishing guide knowledge, attitudes, and behaviours in global recreational fisheriesPublication . Farthing, M. W.; Mann-Lang, J.; Childs, A. R.; Bova, C. S.; Bower, S. D.; Pinder, A. C.; Ferter, K.; Winkler, A. C.; Butler, E. C.; Brownscombe, J. W.; Danylchuk, A. J.; Potts, W. M.Fishing guides are held in high esteem by recreational fishing clients whom they likely influence (for better or worse) through role-modelling. This, coupled with consensus that angler behaviour is a key determinant of ecological outcomes in the catch-and-release (C&R) process suggests exploring the state of fishing guide knowledge, attitudes and behaviour on trips is critical for effective intervention in the global fish crisis. Fishing guides were recruited for an online survey using collaborator networks and social media (n = 342; 47 countries). The survey assessed the guides' knowledge of C&R best practices, attitudes towards environmental behaviours, attitudes towards environmental responsibility and their current practices on guided-angling trips. While most fishing guides were deemed "knowledgeable" (69.0 %) having answered most (>= 4/7) of the best practice questions correctly, many had poor knowledge of key C&R processes such as oesophageal unhooking. Most fishing guides were untrained (64.0 %), and only 8.8 % had accredited training. Fishing guides generally had positive environmental attitudes towards C&R behaviour (50.9-96.2 %), suggesting pro-environmental behavioural intentions. Fishing guides deemed "knowledgeable" had significantly more pro-environmental attitudes towards angling behaviours (p = 0.003), which suggests that best practice training may improve their C&R behaviours. Most fishing guides had pro-environmental attitudes towards their environmental responsibilities (87.1-89.5 %), but these broad attitudes may have little bearing on actual behaviours when faced with a significant trade-off between client satisfaction and ecological integrity. Despite some fishing guides' good knowledge of appropriate behaviours, positive attitudes towards the environment and towards C&R practices, there is room for improvement to meet sustainability goals for C&R fisheries, which may be facilitated through opportunities for best practice training.
- Links between behaviour and metabolic physiology in fishes in the AnthropocenePublication . Bailey, Lauren A.; Childs, Amber R.; James, Nicola C.; Winkler, Alexander; Potts, Warren M.Changes in behaviour and physiology are the primary responses of fishes to anthropogenic impacts such as climate change and over-fishing. Behavioural changes (such as a shift in distribution or changes in phenology) can ensure that a species remains in an environment suited for its optimal physiological performance. However, if fishes are unable to shift their distribution, they are reliant on physiological acclimatization (either by broadening their metabolic curves to tolerate a range of stressors, or by shifting their metabolic curves to maximize their performance at extreme stressors). However, since there are links between fish physiology and behaviour, changes to either of these trait groups may have reciprocal interactions. This paper reviews the current knowledge of the links between the behaviour and aerobic metabolic physiology of fishes, discusses these in the context of exploitation and climate change and makes recommendations for future research needs. The review revealed that our understanding of the links between fish behaviour and metabolic physiology is rudimentary. However, both are hypothesized to be linked to stress responses along the hypothalamic pituitary axis. The link between metabolic physiological capacity and behaviour is particularly important as both determine the response of an individual to a changing climate and are under selection by fisheries. While, it appears that all types of capture fisheries are likely to reduce the adaptive potential of fished populations to climate stressors, angling, which is primarily associated with recreational fishing, may induce the separation of natural populations by removing individuals with bold behavioural traits and potentially the physiological traits required to facilitate behavioural change. Future research should focus on assessing how the links between metabolic physiological capacity and behaviour influence catchability, the response to climate change drivers and post-release recovery. The plasticity of phenotypic traits should be examined under a range of stressors of differing intensity, in several species and life history stages. Future studies should also assess plasticity (fission or fusion) in the phenotypic structuring of social hierarchy and how this influences habitat selection. Ultimately, to fully understand how physiology is influenced by the selective processes driven by fisheries, long-term monitoring of the physiological and behavioural structure of fished populations, their fitness and catch rates are required. This will provide information that can be used by managers to retain behavioural and physiological trait diversity, which will be necessary to improve the resilience of fished populations to the impacts of climate change and safeguard the provision of resources for future generations.
- Incorporating estuarine-angler behaviour and delayed blood sampling into the rapid assessment of catch-and release angling on the iconic dusky kob Argyrosomus japonicusPublication . Butler, Edward C.; Arkert, Nicky K.; Childs, Amber-Robyn; Pringle, Brett A.; Skeeles, Michael R.; Foster, Ryan M.; Farthing, Matthew W.; Winkler, Alexander; Potts, Warren M.Argyrosomus japonicus is arguably South Africa's most important estuarine recreational and small-scale fishery species. Although juvenile A. japonicus predominate in estuarine environments, where catch-and-release angling is common, limited C & R studies have taken place. The aim of this study was to use angler-behaviour to robustly examine the physiological stress response, reflex impairment and short-term (12-36-hour) survival of A. japonicus following C & R angling. Observations of estuarine recreational angling informed three air exposure treatments based on minimum (10 s), mean (75 s) and maximum (240 s) observed times, for use in a controlled angling experiment. Based on a prior laboratory study, blood sampling was delayed 30-40 min post-capture to allow for peak accumulations of lactate and glucose. Long air exposure (240 s) predicted significantly higher blood glucose concentrations (ANOVA, p = 0.03) than short (10 s) exposure. Similarly, both long (p = 0.01) and moderate (75 s; p = 0.01) air exposure significantly predicted elevated blood lactate concentrations, when compared with short exposure. In terms of physical impairment, long air exposure (240 s) had a significant negative influence on the reflex response (cumulative link model, p = 0.01) of A. japonicus. An observed short-term mortality of 7.7% was primarily attributed to hooking injury. To reduce significant physiological and physical stress, it is proposed that anglers should aim to reduce air exposure times to below the observed mean of 75 s, and ideally to 10 s. For relevant and meaningful future C & R studies, we propound the incorporation of angler behavioural assessments, and the investigation of physiological stress responses, prior to designing field studies
- Depth and temperature preferences of meagre, argyrosomus regius, as revealed by satellite telemetryPublication . Winkler, Alexander; Astrid Bovim, Lily; Macena, Bruno C. L.; Gandra, Miguel; Erzini, Karim; Afonso, Pedro; Abecasis, DavidArgyrosomus regius (commonly referred to as meagre), is one of Europe's largest coastal bony fish species and supports important recreational and commercial fisheries in the Atlantic and Mediterranean coasts. Demand for this species, and more recently for their swim bladders, has led to regional population declines and growing importance as an aquaculture species. Despite intense research in captivity, little is known about the spatial ecology of A. regius's wild population, including basic information such as vertical migrations and depth/temperature preferences. Previous research based on indirect data suggests a seasonal habitat shift from shallow to deeper waters, but this has never been validated through direct high-resolution movement data. In this study, we tagged 13 adult A. regius with pop-up satellite archival tags in the South of Portugal, which successfully returned data from 11 individuals including high-resolution data from six recovered tags (mean, range: 167 days, 28-301 days). We found that adults of this population spend 95.2% of their time between 5 and 75 m depth (mean +/- SD, 30.9m +/- 18.3m) and do not venture beyond 125 m. Across seasons, A. regius move across water temperatures between 13.3 and 24.8 degrees C with a preferred thermal range between 14 and 18 degrees C where they spent 75.4% of their time. The inferential modelling using this electronic data validated previous hypotheses by showing significant differences between a shallower and warmer summer habitat vs. a deeper and cooler winter habitat. Visual investigation of the diel effects on depth preferences suggests subtle changes in depth use between day and night during the warmer months of the year. We speculate that these patterns are in response to the species' behavioural ecology and physiology, reflecting the seasonal changes in water stratification and presence of prey, as well as on the species reproduction, which results in summer spawning aggregations in shallower areas.
- Transdisciplinarity in transformative ocean governance research—reflections of early career researchersPublication . Strand, Mia; Ortega-Cisneros, Kelly; Niner, Holly J; Wahome, Michel; Bell, James; Currie, Jock C; Hamukuaya, Hashali; La Bianca, Giulia; Lancaster, Alana M S N; Maseka, Ntemesha; McDonald, Lisa; McQuaid, Kirsty; Samuel, Marly M; Winkler, AlexanderThis paper interrogates the concept of transdisciplinarity, both theoretically and practically, from a perspective of early career researchers (ECRs) in transformative ocean governance research. Aiming to advance research methodologies for future complex sustainability challenges, the paper seeks to illuminate some common uncertainties and challenges surrounding transdisciplinarity from a marine science perspective. Following a literature review on transdisciplinary research, workshops, and a series of surveys, we determine that transdisciplinarity appears to be a concept in search of definition, and that there is a need to explore transdisciplinarity specifically from an ocean research perspective. The paper discusses a number of challenges experienced by ECRs in conducting transdisciplinary research and provides recommendations for both ECRs wishing to undertake more equitable transdisciplinary research and for the UN Decade for Ocean Science to support ECRs in this endeavour (). Based on our findings, we interrogate the role of non-academic collaborators in transdisciplinary research and argue that future transdisciplinarity will need to address power imbalances in existing research methods to achieve knowledge co-production, as opposed to knowledge integration.
- The emergence of marine recreational drone fishing: regional trends and emerging concernsPublication . Winkler, Alexander; Butler, Edward C.; Attwood, Colin G.; Mann, Bruce Q.; Potts, Warren M.Online evidence suggests that there has been an increase in interest of using unmanned aerial vehicles or drones during land-based marine recreational fishing. In the absence of reliable monitoring programs, this study used unconventional publicly available online monitoring methodologies to estimate the growing interest, global extent, catch composition and governance of this practice. Results indicated a 357% spike in interest during 2016 primarily in New Zealand, South Africa and Australia. From an ecological perspective, many species targeted by drone fishers are vulnerable to overexploitation, while released fishes may experience heightened stress and mortality. From a social perspective, the ethics of drone fishing are being increasingly questioned by many recreational anglers and we forecast the potential for increased conflict with other beach users. In terms of governance, no resource use legislation specifically directed at recreational drone fishing was found. These findings suggest that drone fishing warrants prioritised research and management consideration.
- Small coastal marine protected areas offer recurring, seasonal protection to the common stingray (Dasyatis pastinaca)Publication . Kraft, Sebastian; Winkler, Alexander; Abecasis, DavidMarine protected areas (MPAs) are a crucial tool in safeguarding marine biodiversity. However, elasmobranchs are often not the primary protection target of MPAs, and their contribution to protect these species remains to be better understood. In this study we examine the movement patterns of common stingrays in the Professor Luiz Saldanha marine park, a Portuguese temperate coastal MPA. Using acoustic telemetry, we tagged 31 common stingrays and analyzed their spatial and temporal distribution within the MPA and adjacent areas using a long-term data set. Our findings indicate that this species exhibits seasonal site fidelity, with greater presence during the colder months and reduced presence during warmer months. Space use areas did not exceed the size of the fully protected area, and nocturnal and crepuscular activity was significantly higher than during daytime. Additionally, we observed that most individuals seasonally migrated between this MPA and the nearby Sado estuary, likely to reproduce in the latter. These results demonstrate the site fidelity of common stingrays to an area within the marine park, however the protection provided is only seasonal. Seasonal protection of the movement corridor between the marine park and the estuary would improve the management of this species.
- Tagging mortality in acoustic telemetry studies: insights from a multispecies analysisPublication . Martínez Ramírez, Lucas; Bentes, Luis; Dias Almeida Cardoso, André Filipe; Erzini, Karim; Gandra, Miguel; Kraft, Sebastian; Winkler, Alexander; Abecasis, DavidThe widespread adoption of acoustic telemetry has transformed our understanding of marine species' behavior and movement ecology. However, accurately interpreting telemetry data, especially concerning tagging mortality, is essential for drawing valid conclusions. In this study, we scrutinized tagging mortality in 223 individuals across 14 species and evaluated the impact of tagging methodologies, including capture method and size effects. Results reveal high tagging survival rates overall, attributable to the resiliency of the studied species and the rigorous animal welfare protocols followed during tagging procedures. Our results highlight the importance of tailoring array designs to the specific mobility patterns of the studied species for accurate survival assessments. This research contributes to generalizing mortality assessments and clearing the path for more precise and reliable telemetry studies in the future.