Tagged Individuals Research Articles

Using Rhodamine to Tag Mites for Studies of Pre- and Post-Copulatory Sexual Selection.

Our understanding of sexual selection is advancing with new technologies that tag individuals or their sperm, revealing how females use post-copulatory processes to discriminate between competing mates. Many tagging methods have been devised primarily for model insect organisms like Drosophila or Gryllidae. Developing such novel methods, however, is expensive and requires intensive investment. In this experiment, we trial the use of Rhodamine B (RhB) and Rhodamine 110 (Rh110) in a small arachnid, the bulb mite Rhizoglyphus echinopus, for pre- and post-copulatory observations as it is a relatively inexpensive and simple way to tag individuals and their ejaculate proteins. First, we tested whether RhB and Rh110 applied to food can be used as a tagging method to track and distinguish between individuals. Second, we explored whether Rhodamine applied in this way can be used to track sperm transfer. We found that both tagging probes worked well in tagging individuals and that we were able to distinguish between individuals using both LED and fluorescent microscopy. We also found that Rhodamine degraded rapidly in the animals, likely due to their fast metabolism. Due to the rapid degradation, we observed variable results in the sperm transfer trials. We suggest multiple uses for Rhodamine and highlight other invertebrates where this method may come into use for the study of sexual selection.

Stopover habitat use of coastal Pied Avocet revealed by satellite tracking and remote sensing technology

Stopover sites identification for migratory waterbirds is important in China’s coastal wetlands, which have experienced a massive loss of natural wetlands in recent decades. Taking the Pied Avocet (Recurvirostra avosetta), a common waterbird in China’s coastal zone as an example, our research focused on their stopover habitat use based on satellite tracking and remote sensing technology. Along the coast, a total of 6 critical stopover sites, duration of stay more than 14 days, were recognized during their 2022–2023 autumn and spring migrations of the 4 tagged individuals. The results showed that Pied Avocets used habitats close to the coastline and water source, at low elevation, and with sparse vegetation. They also had a certain tolerance for human interference. From the perspective of the land use and land cover type, the proportion (33.01 %) of artificial wetlands including paddy, salt pan, and mariculture has exceeded that (27.97 %) of natural wetlands such as bottomland, tidal flat, estuarine waters, and shallow water in the home ranges of the 6 stopover areas. The study emphasized that the habitat function of artificial wetland should be paid enough attention to while maintaining the natural wetland without further loss. In addition, habitat-oriented management suggestions were put forward for artificial wetlands. This study can provide data and technical support for the conservation and management of waterbirds stopovers, also having reference value for other species.

Bayesian estimation of spatially varying mortality risk using tagged animal data

Abstract The survival of animals is impacted by landscapes of spatially varying mortality factors including habitat type, predation risk or harvest risk, among others. Characterization of these spatial mortality processes is important for managing animal populations and their habitats, yet this information has proved challenging to capture. Advances in telemetry now make it possible to monitor tagged individuals' locations through time for a wide range of taxa, providing opportunity to assess movement and mortality simultaneously through spatial time‐to‐event data. Existing time‐to‐event modelling frameworks have largely ignored spatially varying mortality processes or have treated an animal's location as fixed at a regional level. Here we present a general spatial survival model for analysing time‐to‐event data arising from animal telemetry. Our model has a flexible Cox regression form and can estimate the effects of conventional non‐spatial risk factors (size, seasonality, etc.), spatial covariates (e.g. habitat type) and spatial variation in risk not explained by covariates on mortality. We show how to fit our model using Bayesian methods and demonstrate applications of our model with several simulated examples and two animal telemetry case studies. Our model produced consistent and unbiased parameter estimates throughout simulations with a variety of spatial and non‐spatial hazards. In the first case study, data from 147 tagged caribou in British Columbia, Canada, revealed a spatially heterogeneous mortality landscape with caribou survival varying by elevation, likely in response to space use by predators. Our second case study involved a dataset of 390 acoustically tagged Atlantic cod in a southern Norwegian fjord where a marine protected area (MPA) was established during the study. We found that the MPA led to a shift from mostly fishing mortality to mostly natural mortality within the fjord and that these risks had markedly different spatial hazard patterns. Our spatial time‐to‐event model can make use of data from a variety of widely used telemetry technologies to characterize landscapes of mortality risks for different taxa. Our work provides new opportunities to inform the spatial ecology and management of fish and wildlife populations.

Long-term co-occurrence and gregariousness in the migratory common stingray using network analysis

Aggregations and social interactions play an important role in the movement ecology of many animals, including elasmobranchs. Several of these species have shown the capability of carrying out complex social behaviours, and the importance of sociality in this taxon is being realized. Although it is a growing field of study in the case of these organisms, these processes still need to be better understood, especially to support management and conservation policies. In this study, a long-term acoustic telemetry data set collected on Dasyatis pastinaca in a coastal marine protected area was analysed. A co-occurrence network analysis was done to investigate preferential associations among individuals, revealing non-random associations among them. The analysis revealed a few strong and consistent associations that were maintained across inter-migratory periods, as this species performs seasonal migrations to a nearby estuary, suggesting temporal stability of the observed associations. Moreover, individuals had similar average positions and a generally high overlap of space use in both periods, indicating some level of site fidelity to the fully protected area. Groups of up to 64% of tagged individuals were co-detected at a same receiver, particularly in the western side of the array. Despite our limited sample size, likely underestimating associations, these results show that in addition to their large-scale movement pattern, D. pastinaca is likely to also present active partner preference and spatial structure at a finer spatial scale. The nature of such results is relevant to support the protection of these species.

Half a century of citizen science tag-recapture data reveals stock delineation and cross-jurisdictional connectivity of an iconic pelagic fish

Tag-recapture programs to monitor the movements of fish populations are among some of the longest-running citizen-science datasets to date. Here, using half a century of yellowtail kingfish (Seriola lalandi, Carangidae) tag-recapture data collected through citizen-science projects, we report novel insights into population connectivity in Australia and New Zealand (NZ). Despite the importance of kingfish in commercial and recreational fisheries, substantial knowledge gaps about their stock structure and connectivity between jurisdictions hinder current management efforts. Between 1974 and 2022, 63,432 releases and 4636 recaptures (7.3%) of tagged kingfish were collected in Australia and NZ. Most tagged individuals (51.4%) were recaptured within 10 km of their original release location up to 14 years post-release (mean: 225 days), indicating some degree of site fidelity. However, 656 (14.2%) kingfish were recaptured over 100 km from their release location, with one fish travelling at least 2834 km in 702 days. Seasonal variability was evident for releases and recaptures, with more releases occurring in summer and autumn in most jurisdictions. Network analysis of recaptures revealed no connectivity between tagged kingfish from western and eastern Australia, supporting genetic delineation. By contrast, extensive connectivity exists across eastern Australia and NZ, with 87 kingfish moving between five Australian state jurisdictions, 316 individuals travelling across 15 bioregions and six kingfish moving between Australia and NZ. Our findings provide important new insights into the structure and connectivity of the eastern Australia kingfish stock and suggest increased collaboration between state and international fisheries jurisdictions may support improved stock assessment and management.

Aggregative versus solitary settlement in Spirobranchus cariniferus gray, 1843 (serpulinae). What is the trade-off?

Sessile marine invertebrates usually follow a distinct pattern of living in dense aggregations or as solitary individuals. However, at least some serpulins, including Spirobranchus cariniferus, seem to be able to settle aggregative or solitary. To understand how living solitary or in aggregation is beneficial, it is essential to understand the advantages and disadvantages of both settlement strategies for sessile invertebrates. Benefits of living in aggregations include securing suitable habitat, improving the probability of survival by mitigating physical stress and increasing reproductive success.However, living in patches also comes with some disadvantages for the individual, such as higher intra- and interspecific competition for food, space and oxygen. Increased physiological stress can lead to increased mortality and decreased reproductive success, whereas solitary individuals could produce more gametes because of a lack of competition for food and space. On the other hand, predators would have easier access to them, and the possibility of fertilisation success may be lower because of a lack of synchronisation and a greater distance between individuals of different sexes.These issues have not been sufficiently addressed, particularly for serpulids. Individuals of the New Zealand endemic polychaete Spirobranchus cariniferus can be found solitary and aggregative in the same habitat. Therefore, this study is the first on serpulids comparing the growth and mortality of individuals living alone or in aggregations. Hence, bi-monthly observation of mortality and growth measurements were conducted on tagged individuals in the field, and weekly observations were conducted in a laboratory-based study on individuals of both settlement configurations. A final comparison of body metrics to tube dimensions was made by removing an individual from their tube.My findings revealed that while solitary and aggregative individuals elongate their tubes at a similar rate, further correlations of the body to tube sizes lead to the conclusion that solitary worms focus more of their energy on tube growth rather than body size increment than aggregative conspecifics. Mortality is highly variable and seems not to differ between both configurations. However, individuals living in a patch can better recover from damage to their tubes. Here presented observations hopefully initiated further studies into the effects of aggregation size and density on individual growth. Results of this and subsequent studies can inform the management efforts for reefs of serpulins, bivalves and other invertebrates.

An Examination of the Effects of Dorsal Fin-Mounted SPOT on Carcharodon carcharias, the Great White Shark

This opinion piece presents empirical evidence to examine possible negative consequences of the use of penetrative tagging as used on the great white shark (GWS). Tagging programs currently using this method attach SPOT (Spatial Positioning Only Tags) using corrodible bolts inserted through the dorsal fin while the shark is taken out of water. Such methods can cause harm to the tagged individual. Possible adverse effects include impacts on growth, tag biofouling, wounds, heightened stress, and hemorrhaging. This method may adversely impact dorsal fin structure and the shark’s hydrodynamics. As a result, data collected may not be reflective of natural behavior. Bolted SPOT are semi-permanently affixed to the shark but can have a battery life of approximately 3.5 years. Most of these tags (69%) ceased transmitting in less than 2 years. Alternative tagging technologies exist as more humane options.

Monitoring post-spawning movement, habitat use, and survival of adult anadromous rainbow smelt using acoustic telemetry in a New Hampshire estuary.

Anadromous rainbow smelt (Osmerus mordax, [Mitchill 1814]) are found along the northeast Atlantic coastline of North America, with their range now limited to north of Cape Cod, Massachusetts, USA. Although their anadromous life cycles are described broadly, gaps remain regarding how adult rainbow smelt use estuaries post-spawning, including movement behaviors, habitats used, and specific timing of emigration to coastal waters. In spring 2021, we used acoustic telemetry to characterize movements during and after the spawning season of rainbow smelt captured in tributaries to Great Bay, New Hampshire, USA, a large estuarine system near the southern edge of their range. Forty-four adult rainbow smelt (n = 35 male, n = 9 female) were tagged with Innovasea V5 180-kHz transmitters and an array of 22,180 kHz VR2W receivers were deployed throughout Great Bay to detect movements of tagged fish from March to October 2021. Rainbow smelt were detected 14,186 times on acoustic telemetry receivers, with 41 (93%) of the tagged individuals being detected at least once post-tagging. Individuals were detected moving between tributaries, revealing that rainbow smelt can use multiple rivers during the spawning season (March-April). Mark-recapture Cormack-Jolly-Seber models estimated 83% (95% confidence interval 66%-92%) of rainbow smelt survived to the mainstem Piscataqua River, and a minimum of 50% (22 of 44) reached the seaward-most receivers and were presumed to have survived emigration. Most individuals that survived remained in the estuary for multiple weeks (average = 19.47 ± 1.99 standard error days), displaying extended use of estuarine environments. Downstream movements occurred more frequently during ebb tides and upstream movements with flood tides, possibly a mechanism to reduce energy expenditures. Fish emigrated from the estuary by mid-May to the coastal Gulf of Maine. Our results underscore that rainbow smelt need access to a variety of habitats, including multiple tributaries and high-quality estuarine habitat, to complete their life cycle.

Lower thermal tolerance restricts vertical distributions for juvenile albacore tuna (Thunnus alalunga) in the northern limit of their habitats

IntroductionEvaluating the thermal tolerance of commercially valuable tuna species and their behavioral responses to the limits of this tolerance is essential for evaluating the effects of changes in water temperature driven by global climate change on their distribution and fisheries. We aimed to identify the lower thermal tolerance (Tmin) of juvenile albacore tuna (ALB) and evaluate their behavioral response to Tmin by focusing on wild behavior in the northern distributional limit. Additionally, we investigated how vertical behavior is linked to the vulnerability of ALB to Japanese longline (LL) and pole-and-line (PL) fisheries.MethodsWe explored the swimming depths and water temperatures of four previously reported tagged individuals migrating from subtropical to temperate areas and identified Tmin and its depths in the water column as unfavorable depths (DTmin). To investigate the spatial patterns of ALB fishery grounds for LL and PL fisheries, we analyzed hotspots specific to each type of gear using the historical Japanese fishery logbook for both fisheries.ResultsComparisons of the fishery grounds between the two fisheries revealed that PL hotspots appeared in the northern areas, while LL hotspots were in the southern regions. We also discovered that the vertical distribution of ALB became shallow in high-latitude areas, which were strongly affected by DTmin shallowing at high latitudes.DiscussionThese results provide evidence of a behavioral response among juvenile ALB that avoids Tmin by remaining at the surface. We discuss the implications of the results for latitudinal changes in the vulnerability of ALB to fisheries in terms of the overlapping depth between ALB vertical habitats and the gear-setting depth for each fishery.

Effectiveness of fishways on the Pinka Stream and the Rába River, Central Europe: An evaluation with species from the order Cypriniformes

AbstractThis study assessed the functional effectiveness in terms of passage proportion of three fishways, one nature‐like bypass, one partly nature‐like bypass and partly technical pool‐type and one completely technical, on the Pinka Stream and Rába River in Western Hungary. Radio frequency identification with passive integrated transponder tagging was used to collect data on the upstream passage. A total of 2976 tagged individuals were included in the study; 2863 individuals were either barbel (Barbus barbus), nase (Chondrostoma nasus) or chub (Squalius cephalus), which were chosen as model species, and 113 individuals belonged to four other species. There were 540 individuals of the model species and 18 individuals of the other species detected while successfully ascending one of the fishways. The time‐to‐event (survival) analysis of the data of the model species revealed significant species‐specific differences in passage probability between the fishways. The passage probabilities of the barbel were the highest, and those of the nase were the lowest at all three fishways. The findings demonstrate that single‐species evaluations can lead to incorrect conclusions on fishway effectiveness. Technical fishways can be as effective as nature‐like ones, and hybrid solutions (technical fishways combined with nature‐like bypasses) can function as well. The limitations of the study and recommendations for further evaluations are also discussed.

Effects of capture and GPS-tagging in spring on migration timing and reproduction in Pink-footed geese Anser brachyrhynchus

BackgroundGPS-transmitters enable detailed study of animal behaviour but may impact the animals. Impacts vary from short-term stress and habituation to longer-term effects on e.g., migration and reproduction. To study impacts, ideally, true controls (i.e., uncaptured or untagged animals) are used, but unbiased assessments of their migration timing and breeding performance are challenging, especially in remote areas. Alternatively, quasi-controls can be used: individuals tagged longer ago, or the same tagged individuals but in later years. Quasi-controls reveal tagging effects that differ between the first and following years.ResultsWe captured Pink-footed geese (Anser brachyrhynchus) in spring and summer and deployed GPS-transmitter neckbands. In spring, geese were caught with cannon or clap nets on stopovers in Norway and Finland, 2 weeks before departure to breeding areas in Svalbard and Novaya Zemlya. In summer, geese were rounded up during wing moult in Svalbard. First, we compared geese tagged recently in spring with geese tagged in spring or summer 1–4 years prior. Newly tagged geese migrated significantly later, by 2 days, than previously tagged geese, both at departure from the spring stopover and arrival to the breeding grounds, while migration duration did not differ. Breeding propensity and laying date did not differ, but nesting success tended to be lowered, resulting in a significantly lower annual probability to produce hatchlings in recently tagged geese than in previously tagged geese. Second, within individuals tagged in spring, spring migration advanced in their next year, suggesting delay in their first spring. This was likely not an ageing effect, as geese tagged in summer showed no advancing spring migration timing over the years. Third, in Svalbard, observed brood sizes of geese tagged in summer and untagged geese did not differ 1 year after tagging.ConclusionsThe capture and GPS-tagging of geese 2 weeks before spring departure delayed their spring migration and lowered their probability to produce hatchlings in that year. These effects lasted longer than previously reported week-long effects of GPS-tagging on time budgets in summer and of neck-banding on spring body condition. Additional study is needed to evaluate longer-term or permanent effects which remain undetected with quasi-controls.

Predicting juvenile-to-adult survival in Chinook salmon using non-lethal scale-derived growth and regeneration indices

ABSTRACT Survival is often associated with body size, growth rate, and stress, but the latter two are more difficult to observe non-lethally. Non-lethal methods can be particularly important for endangered and culturally valuable species. With fish scales, growth and stress indices could be inferred without needing to sacrifice fish. We examined scales from ~350 wild Chinook salmon (Oncorhynchus tshawytscha) in Valley Creek and at Lower Granite Dam (Pacific Northwest, USA) in 2007–2019. From a von Bertalanffy model and scale circulus spacings, we estimated a brood-year-specific growth coefficient K (hereafter K ˆ ). Using the scale-derived K ˆ and other biological and environmental covariates, we examined how these potential predictors associated with juvenile-to-adult survival of >136,000 passive-integrated-transponder-tagged Chinook salmon from the Snake River Basin (Pacific Northwest, USA). We found that the effects on survival from brood-year-specific K ˆ , fork length of the tagged individuals, and interaction between K ˆ and fork length were positive. We also determined that the proportion of fish samples with regenerated scales (an indicator of stress) had a negative effect on survival. For further refinement of non-lethal, scale-derived indices on survival, we encourage examination of indices across populations, juvenile habitats, and juvenile life stages, and not simply a regional, brood-year-specific growth index.

Balancing risks and rewards of alternate strategies in the seaward extent, duration and timing of fjord use in contemporary anadromy of brown trout (Salmo trutta)

BackgroundAnadromy comprises a successful life-cycle adaptation for salmonids, with marine migration providing improved feeding opportunities and thus improved growth. These rewards are balanced against costs from increased energy expenditure and mortality risk. Anthropogenic-induced environmental changes that reduce benefits and/or increase costs of migration e.g., aquaculture and hydropower, may therefore result in adaptations disfavouring anadromy. We tagged brown trout (Salmo trutta) smolts (N = 175) and veteran migrants (N = 342), from five adjacent riverine populations located in Sognefjorden, the longest Norwegian fjord-system supporting anadromous brown trout populations (209 km). Over four years, 138 acoustic telemetry receivers were deployed to track migrations of tagged individuals from freshwater and throughout Sognefjorden. Detected movements were used to fit migration models and multi-state mark-recapture models of survival and movement for each life-stage. Seaward migration distance was modelled to examine the fitness consequences from alternate migration strategies, with these models used to simulate the extent of fjord-use by individuals and accompanying growth, fecundity and survival consequences. We compared these findings with mark-recapture data collected prior to aquaculture and hydropower development.ResultsThe telemetry data revealed that the outermost-fjord region was utilised by all populations albeit by few individuals. However, historical recaptures were located at a greater distance from the river mouth (87.7 ± 70.3 km), when compared to maximum migration distances of present-day counterparts (58.6 ± 54.9 km). River of origin influenced observed migratory behaviour and differential survival was estimated for each population and life-stage. The simulations based on telemetry-data models revealed a 30% and 23% difference in survival among populations for smolts and veteran migrants, respectively. At the individual-level, a long-distance migration strategy was rewarded with enhanced fecundity. However, the main contribution to population-level fecundity was overwhelmingly derived from middle-distance migrants, due to higher mortality rates and limited numbers of long-distant migrants.ConclusionsWe conclude that present-day anadromy is precarious, but potential risk varies considerably between life-stages and populations, even within a single fjord system. Our findings suggest that selection for extended migration is under pressure, we therefore stress the importance of monitoring and management actions to secure genetic variation pertinent to preserve fitness gains of anadromy.

Using PIT tags to infer bat reproductive status and parturition date: busy nights during lactation

Abstract Passive integrated transponders (PIT tags) can aid in the collection of important demographic data for species for which other methods, such as GPS technology, are not suitable. PIT tags can be particularly suitable to monitor small and cryptic species like bats and permit inference on their behavioral ecology. Literature for several species of bats states that females change their nightly activity patterns—going out and in of the roost only once per night during gestation compared to several times during lactation. Hence, we tested whether PIT tag detection patterns could be used to infer reproductive status and parturition date of female bats. From 2017 to 2021, we recorded detections of PIT-tagged little brown (Myotis lucifugus) and northern long-eared bats (M. septentrionalis) at the entrance of 2 maternity roosts in Québec and Newfoundland, Canada. We also used the maternity roost in Québec as a case study to further evaluate the potential of this method to link behavior and demography and investigated factors affecting parturition date. We were able to infer reproductive status for 63% to 97% of tagged individuals detected during both the gestation and the lactation periods, and parturition date for 61% to 95% of reproductive individuals, depending on the year and roost. Early spring arrival at the roost and warm spring mean temperature at night were associated with earlier parturition dates. Herein, we highlight that PIT tag systems may be useful to detect changes in activity patterns of female bats and infer individual reproductive parameters, which is on the long-term less stressful for bats and easier for researchers. We demonstrate that this approach is useful to investigate intrinsic and extrinsic factors of reproductive parameters, improving our understanding of bat population dynamics resulting in more informed population management decisions.

Evaluation of tag attachment techniques for plunge‐diving terns

A wide variety of attachment techniques have been used to track birds with electronic tags, with glue, tape, leg rings, neck collars and harnesses being the most common methods. In general, the choice of attachment method should strive to minimize tagging effects, but ensure that sufficient data are collected to address the research question at hand. The aim of our study was to develop and evaluate tag attachment methods to track Sandwich Terns Thalasseus sandvicensis during the last part of the incubation and the chick‐rearing period of one breeding season. Tag attachments had to stay on for the duration of the chick‐rearing period (5–6 weeks) and be non‐restraining and flexible, but strong enough to withstand the forces and submersion associated with their plunge‐diving foraging technique. We first experimentally tested the durability of flexible material under various environmental conditions with the aim of developing a self‐releasing harness. Then, in field studies, we compared three different attachment methods on terns during the breeding seasons, attaching tags to dorsal feathers using (1) tape, (2) glue or (3) a newly developed harness made specifically for short‐term deployments of one chick‐rearing period and constructed from degradable material. Assessment of the performance of attachment methods was based on retention time of the loggers and on annual survival rates of tagged individuals in comparison with non‐tagged individuals. The use of tape and glue led to premature loss of tags (median minimum retention time (range) of 3 (1–4) days and 15 (5–26) days, respectively), whereas the self‐releasing harness had a median minimum retention time of 42 (18–91) days, which is sufficient to track Sandwich Terns during the entire chick‐rearing period. The apparent annual survival of birds tagged using glue or tape did not differ from that observed in non‐tagged control birds. In contrast, birds fitted with the self‐releasing harnesses might have experienced a lower survival rate than control birds. Entanglement of birds in the harness material was incidentally observed in three cases, which may have contributed to the lower survival rates observed in this group. The risk of entanglement can potentially be mitigated with a leg‐loop harness instead of a full‐body harness. Our results highlight the necessity of careful consideration when selecting appropriate attachment methods. Specifically, there is a need to address whether the research questions and desired tracking duration justify the use of a harness and the higher impact that it entails, or whether a tape or glue‐mount is sufficient. More broadly, sharing field expertise in tag attachments across studies is essential to successful deployments while minimizing the impact on animals.

Migration timing and marine space use of an anadromous Arctic fish (Arctic Char, Salvelinus alpinus) revealed by local spatial statistics and network analysis.

The ice-free season (typically late-June to early-October) is crucial for anadromous species of fish in the Arctic, including Arctic Char (Salvelinus alpinus), which must acquire adequate resources for growth, reproduction, and survival during a brief period of feeding in the marine environment. Arctic Char is an important food fish for Inuit communities across the Arctic. Understanding drivers and patterns of migration in the marine environment is thus essential for conservation and management of the species. We used passive acoustic telemetry to characterize migration patterns of 51 individual anadromous Arctic Char during the ice-free season in the marine environment of Coronation Gulf (Nunavut, Canada; 2019-2022). Based on recent genetic evidence, some tagged individuals were likely Dolly Varden (Salvelinus malma malma), a closely related species to Arctic Char. Using local Getis G* and network analysis, we described movement patterns and identified high-use locations in the marine environment. We also related freshwater overwintering location to migration timing and movement pattern. Comparing groups of fish that overwintered in distinct locations, we found: (i) limited evidence that marine movements were associated with overwintering location; (ii) minor differences in use of marine space; and, (iii) timing of freshwater return differed significantly between overwintering groups, and was related to length and difficulty of the migratory pathway in freshwater. Results from both network analysis and local Getis G* revealed that, regardless of overwintering location, coastal locations were highly used by fish. Overwintering locations, and the migratory routes to access overwintering locations, affect the timing of freshwater return. Preference of fish for coastal marine locations is likely due to abundance of forage and patterns in break-up of sea ice. Similarities in marine space use and movement patterns present challenges for managing this and other mixed stock fisheries of anadromous Salvelinus spp. Absences or periods of time when fish were not detected prevented comprehensive assessment of movement patterns. Local Getis G*, a local indicator of spatial association, is a helpful tool in identifying locations associated with absences in acoustic telemetry arrays, and is a complementary method to network analysis.

Twenty-four-year investigation of the reproductive biology of Glis glis in England (Rodentia: Gliridae)

Nest boxes were used to monitor a population of edible dormice (Glis glis) for 24 years. Details were recorded of reproductive condition, age and co-habitation by ca. 10,000 tagged individuals. Age at first breeding, periodic failure to breed, ‘absenteeism’ among adults, changing litter size with growth of young, survival rates and lifetime reproductive output were documented. The proportion of communal breeders and their kinship was examined as well as the occurrence of breeding by subadults. Life strategy and potential benefits of seasonal and annual behaviour are discussed.

Effect of 12 mm PIT tags on the survival, growth, and ecologically significant behaviours of juvenile critically endangered endemic Zingel asper

Understanding the movement ecology and habitat use of freshwater fish is crucial for their conservation, with telemetry being an essential tool. Current tagging methods are restricted by the minimum body size of fish, as tags should not exceed 2% of the fish's body mass. This limitation hinders the study of juvenile small-bodied endangered species, as the reduced fitness of tagged individuals can negatively impact their populations. This study examines the feasibility of using 12-mm PIT tags on juvenile and subadult individuals (63–90 mm fork length) of the critically endangered Rhône streber, Zingel asper. Results indicate that tagging does not significantly affect survival, growth or behavioural traits, despite the tag weight being between 2.2% and 5.4% of the fish's weight. Tag retention was 100%, with 90% of individuals having the PIT tag fully encapsulated in the body cavity wall after 55 days. The only possible negative effect observed was a tendency, albeit statistically non-significant, for slower escape velocity in the smallest tagged individuals. These findings reduce the known minimum body size limit for 12-mm PIT tags for this species. However, the smallest individuals may be more sensitive to tagging, warranting careful consideration to avoid potential negative impacts on wild populations.

The smaller, the better? First evaluation of growth and mortality in crayfish internally tagged with p-Chips

Abstract Small-bodied aquatic animals present a challenge to researchers seeking to uniquely mark individuals for scientific study. Microtransponder tags, such as p-Chips, represent the smallest electronic animal tags available to meet this need. The use of p-Chips to tag freshwater crayfishes, however, has not been explored. The goal of this study, therefore, was to determine the effects of p-Chip tagging on growth and survival of crayfishes in a controlled laboratory environment. We also investigated potential influences from variables such as sex, reproductive form, number of molt events, and crayfish size on mortality. We internally tagged individuals of the woodland crayfish Faxonius hylas (Faxon, 1890) (12.2–26.6 mm carapace length; CL) with either one p-Chip (single-tag) or one p-Chip and one visual implant elastomer tag (double-tagged) and observed the effects over a period of 90 days. Survival probability over time was not statistically different (P > 0.05) among tagging groups, sex, and reproductive form. Survival rates were similar across all tagging groups, with 75% in the control group, 77% in the double-tagged group, and 78% in the single-tag group. A strong correlation, however, was observed between survival and the number of molt events. Additionally, there was a negative correlation between survival and crayfish size (CL), indicating a higher risk of mortality for larger individuals. There were no statistically significant differences in growth in CL (P = 0.30) or mass (P = 0.19) among the tagging groups. We conclude that p-Chips are a viable tagging option for the study of crayfishes given their size, readability, and retention through molting cycles. We recommend that future studies repeat this experiment using smaller individuals to determine the minimum crayfish size compatible with p-Chip tagging. It is also important to test p-Chips with other crayfish species and compare the growth and mortality of crayfish tagged with p-Chips in natural habitats.

Individual residency behaviours and seasonal long-distance movements in acoustically tagged Caribbean reef sharks in the Cayman Islands.

Understanding how reef-associated sharks use coastal waters through their ontogeny is important for their effective conservation and management. This study used the horizontal movements of acoustically tagged Caribbean reef sharks (Carcharhinus perezi) to examine their use of coastal space around the Cayman Islands between 2009 and 2019. A total of 39 (59.1%) tagged sharks (male = 22, female = 17, immature = 18, mature = 21) were detected on the islands wide network of acoustic receivers. The detection data were used to calculate values of Residency Index (RI), Site-Fidelity Index (SFI) and minimum linear displacement (MLD), as well as for network analysis of individual shark movements to test for differences between demographics, seasons, and diel periods. Sharks were detected for up to 1,598 days post-tagging and some individuals showed resident behaviour but the majority of tagged individuals appear to have been one-off or only occasional transient visitors to the area. Generally, individuals showed strong site-fidelity to different areas displaying linear home ranges of < 20 km. The evidence indicates that there was no pattern of diel behaviour. Tagged sharks generally showed increased movements within and between islands during the summer (April-September), which may be related to breeding activity. Some individuals even made occasional excursions across 110 km of open water > 2,000 m deep between Grand Cayman and Little Cayman. One mature female shark showed a displacement of 148.21 km, the greatest distance reported for this species. The data shows that the distances over which some sharks moved, greatly exceeded the extent of any one of the islands' marine protected areas indicating that this species may be more mobile and dispersive than previously thought. This study provides support for the blanket protection to all sharks throughout Cayman waters, which was incorporated within the National Conservation Act in 2015.