Individual isotopic specializations predict subsequent inter-individual variation in movement in a freshwater fish

Despite many similarities and intuitive links between individual dietary specialization and behavioral inter-individual variation, these phenomena have been studied in isolation, and empirical data confirming relationships between these intraspecific variance sources are lacking. Here we use stable isotope analysis and acoustic telemetry to test the hypothesis that individual specialization in trophic (d15N) and littoral/pelagic prey reliance (d13C) covary with inter-individual variation in movement in a group of 34 free-swimming burbot (Lota lota). By performing stable isotope analysis on tissues with differing isotopic turnover rates (anal fin and dorsal muscle), in 24 lethally sampled burbot, we demonstrate that individual specialization in trophic niche (d15N) and li

Do fishing education programs effectively transfer 'catch-and-release' best practices to youth anglers yielding measurable improvements in fish condition and survival?

There is growing interest in educating anglers on catch-and-release (C&R) best practices, yet there is little information on whether angler education programs yield measurable improvements in fish condition and survival. As such, we conducted a study focused on mixed-gender youth groups (aged 8-10) and contrasted three levels of training intervention. Treatment 1 training had no mention of C&R best practices. Treatments 2 and 3 trainings involved visual aids to illustrate best practices, while Treatment 3 added a hands-on demonstration. When caught by the most highly trained participants, fish experienced the least amount of air exposure, but were handled for longer periods, as trained anglers were more careful. Higher levels of training led to a higher likelihood that anglers wet their hands and used a bucket filled with water while handling fish but all treatment groups yielded similar incidences of deep hooking and bleeding. Overall, mortality (initial and after ∼12 h) was low across all treatments. Our findings suggest that a short (∼20 min) fishing workshop can transfer information on C&R practices, at least in the short-term, that can lead to some improved conditions for angler-caught fish. It is unclear the extent to which this information is retained in the long-term or how different target populations or training strategies might influence knowledge transfer and adoption and thus biological outcomes. With growing interest in sharing C&R best practices with anglers, we suggest that there is need for additional research on outreach strategies to ensure that such efforts are effective and yield meaningful benefits to fish welfare and conservation

Occupation, body size and sex ratio of round goby (Neogobius melanostomus) in established and newly invaded areas of an Ontario river

Invasive species represent a challenge because the particular characteristics of a species' invasion are often unknown before the invasion. To provide some clarity as to how invasive species demographic structure might change as a population advances its range, we compared the proportion of occupied sites, size structure and sex ratio of round gobies in the area where they first invaded with more recently invaded areas at the extent of their range in a river in south-eastern Ontario. We used a standardized angling technique to sample gobies larger than 45-mm total length in the summer and early autumn of 2007. Round goby at the upstream and downstream extent of their range occupied a lower proportion of randomly selected sites, and contained a wider distribution of sizes as well as significantly larger individuals. Sex ratios in all areas were male-biased and the male-to-female ratio was significantly higher in the upstream segment of the river (2. 2:1) compared to the area of first introduction (1.4:1). The difference between the newly invaded and the established sites suggests that round goby population structure may be affected by density. The results of this study help us further describe the demographic characteristics of biological invasions whilst examples of population structure and behaviour in gobies and other species provide a basis for generating hypotheses for range expansion

Diel habitat use patterns of a marine apex predator (tiger shark, Galeocerdo cuvier) at a high use area exposed to dive tourism

Knowledge of the diel spatial ecology of wild animals is of great interest to ecologists and relevant to resource management and conservation. Sharks are generally considered to be more active during nocturnal periods than during the day; however, few studies have empirically evaluated diel variation in shark habitat use and how anthropogenic disturbances may influence these patterns. In the western central Atlantic Ocean, tiger sharks (Galeocerdo cuvier) are highly abundant in the shallow waters of the Little Bahama Bank, Bahamas. Within the northwest edge of the Bank, there is an area nicknamed “Tiger Beach,” where tiger sharks are provisioned year-roun

Large sharks exhibit varying behavioral responses to major hurricanes

Under global climate change, storm events are predicted to increase in strength and frequency. Although aquatic animals can be affected by acute natural disturbances, information on the immediate consequences of these weather systems on the behavioral ecology of highly mobile aquatic predators remains limited. Here we examine the spatial distributions, activity spaces, and ecological change-points of four large shark species (mean: 193 cm fork length ± 70 SD) via passive acoustic telemetry in two different locations in the subtropical Atlantic (Little Bahama Bank, Bahamas, and Biscayne Bay, Florida, USA) in relation to two separate major hurricane events (category 4 and 5). We tested whether sharks would evacuate shallow coastal habitats (and thus exit the acoustic arrays) during the hurricanes and exhibit comparable size of activity spaces pre- and post-storms, as has been previously found for smaller (50–150 cm fork length) sharks elsewhere. Located on the northwest edge of the Little Bahama Bank, Bahamas, an acoustic array consisting of 32 acoustic telemetry receivers tracking tiger sharks Galeocerdo cuvier sustained a direct hit from Hurricane Matthew in 2016. Daily detections of tagged tiger sharks within the array were consistent before and during the hurricane. Immediately following the storm, daily tiger shark detections approximately doubled. Size and extent of tiger shark activity space within the array were consistent pre- and post-storm. Located off Miami, within Biscayne Bay, an array of 32 acoustic receivers tracking bull Carcharhinus leucas, nurse Ginglymostoma cirratum, and great hammerhead sharks Sphyrna mokarran was exposed to tropical-storm-force winds from Hurricane Irma in 2017. As the eye of the storm passed 140 km to the west, most sharks previously present in the array were no longer detected, while two nurse sharks remained at receivers near Miami. Numbers of tagged bull sharks declined following Hurricane Irma, whereas other species did not. Ecological change point analyses indicated that seasonal changes - rather than storm conditions - cannot be ruled out as the primary driver of post-storm shark behavior. Unlike smaller shark species which have previously been found to evacuate shallow water habitats during storms, we found variable responses of large sharks to storm events. •The behavioral effects of tropical storms have not been evaluated for large shark species.•Acoustic telemetry was used to study the behavior of large sharks at two sites hit by hurricanes.•Species-specific responses were observed.•Several species did not evacuate shallow water as reported in small species.•Interspecific behavior, including why some sharks failed to evacuate stormimpacted areas, is discussed

Parental care in a stressful world: Experimentally elevated cortisol and brood size manipulation influence nest success probability and nest-tending behavior in a wild teleost fish

Parental care is an advantageous reproductive behavior, as the fitness of the caregiver is increased through improving the chances of its offspring’s survival. Parental care occurs in a variety of teleost fishes. The body size of parental fish and the size of their brood can affect nest abandonment decisions, where compared with smaller fish with smaller broods, larger fish with larger broods typically invest more energy into reproductive events because they have less future reproductive potential. Although essential for basal metabolism and body maintenance functions, when glucocorticoid hormones (e.g., cortisol) are chronically elevated, as can occur during stress, fish may experience impairments in behavior and immune function, leading to compromised health and condition. Anthropogenic stressors during parental care can lead to elevated stress, therefore making it necessary to understand how stress influences an already-challenging period. Using smallmouth bass as a model, a gradient of body sizes, and experimentally manipulated brood size (i.e., reducing large broods and supplementing small broods) and cortisol levels (i.e., elevated via slow-release intraperitoneal cocoa butter implants containing cortisol versus controls), we tested the hypothesis that the reproductive success and parental care behaviors (i.e., aggression, nest tending) of nest-guarding male smallmouth bass are influenced by parental body size, brood size, and cortisol level. Overall, there was a relationship between cortisol treatment and nest success in which larger fish exhibited lower success when cortisol levels were elevated. Brood size had a significant effect on fish-tending behavior, independent of cortisol level and body size. Lending partial support to our hypothesis, the results of this study indicate that the reproductive success of guarding male smallmouth bass is influenced by cortisol level and that tending behavior is affected by brood size

Biologgers reveal post-release behavioural impairments of freshwater turtles following interactions with fishing nets

Bycatch, the incidental capture of non-target organisms, occurs in most commercial fisheries. Although immediate bycatch mortality is frequently documented in fisheries, detrimental sub-lethal effects and potential post-release mortality remain largely unknown despite the potential population-level consequences. Turtles are captured as bycatch and their populations are vulnerable to slight increases in adult mortality. In eastern Ontario, turtles are frequently captured as bycatch in a small-scale freshwater commercial fyke-net fishery and, currently, the fate of discarded turtles is unknown. We wished to determine the effect of fyke-net capture on post-release survival and behaviour in eastern musk turtles Sternotherus odoratus and painted turtles Chrysemys picta. We used biologgers equipped with tri-axial acceleration, depth and temperature sensors to document locomotor activity, vertical distribution, and temperature use of entrapped (exposed to forced submergence for 4 h) and control turtles upon release. Overall dynamic body acceleration was used as a measure of post-release activity for the first hour, first 6 h, and first 48 h. Post-release mortality was not detected. Turtles subjected to entrapment exhibited lower activity during the first 6 h following release, and their vertical distribution and temperature use differed in the first 2 h following release, but these effects disappeared after 48 h, suggesting turtles have the ability to recover. Quantifying the post-release mortality and sub-lethal effects of entrapment is important for estimating the population effects associated with bycatch

A moving target - incorporating knowledge of the spatial ecology of fish into the assessment and management of freshwater fish populations

Freshwater fish move vertically and horizontally through the aquatic landscape for a variety of reasons, such as to find and exploit patchy resources or to locate essential habitats (e.g., for spawning). Inherent challenges exist with the assessment of fish populations because they are moving targets. We submit that quantifying and describing the spatial ecology of fish and their habitat is an important component of freshwater fishery assessment and management. With a growing number of tools available for studying the spatial ecology of fishes (e.g., telemetry, population genetics, hydroacoustics, otolith microchemistry, stable isotope analysis), new knowledge can now be generated and incorporated into biological assessment and fishery management. For example, knowing when, where, and how to deploy assessment gears is essential to inform, refine, or calibrate assessment protocols. Such information is also useful for quantifying or avoiding bycatch of imperiled species. Knowledge of habitat connectivity and usage can identify critically important migration corridors and habitats and can be used to improve our understanding of variables that influence spatial structuring of fish populations. Similarly, demographic processes are partly driven by the behavior of fish and mediated by environmental drivers. Information on these processes is critical to the development and application of realistic population dynamics models. Collectively, biological assessment, when informed by knowledge of spatial ecology, can provide managers with the ability to understand how and when fish and their habitats may be exposed to different threats. Naturally, this knowledge helps to better evaluate or develop strategies to protect the long-term viability of fishery production. Failure to understand the spatial ecology of fishes and to incorporate spatiotemporal data can bias population assessments and forecasts and potentially lead to ineffective or counterproductive management actions

Partial diel migration: A facultative migration underpinned by long-term inter-individual variation

The variations in migration that comprise partial diel migrations, putatively occur entirely as a consequence of behavioural flexibility. However, seasonal partial migrations are increasingly recognised to be mediated by a combination of reversible plasticity in response to environmental variation and individual variation due to genetic and environmental effects. Here, we test the hypothesis that while partial diel migration heterogeneity occurs primarily due to short-term within-individual flexibility in behaviour, long-term individual differences in migratory behaviour also underpin this migration variation. Specifically, we use a hierarchical behavioural reaction norm approach to partition within- and among-individual variation in depth use and diel plasticity in depth use, across short- and long-term time-scales, in a group of 47 burbot (Lota lota) tagged with depth-sensing acoustic telemetry transmitters. We found

Spatial ecology of reintroduced walleye (Sander vitreus) in Hamilton Harbour of Lake Ontario

Many coastal embayments in the Laurentian Great Lakes have been subjected to extensive human physical modification and pollution that has led to the loss of freshwater biodiversity. For example, Hamilton Harbour is a large coastal embayment situated at the western end of Lake Ontario, wit