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Physiological stress response, reflex impairment, and survival of five sympatric shark species following experimental capture and release
Abstract
In many fisheries, some component of the catch is usually released. Quantifying the
effects of capture and release on fish survival is critical for determining which practices are sustainable,
particularly for threatened species. Using a standardized fishing technique, we studied
sublethal (blood physiology and reflex impairment assessment) and lethal (post-release mortality
with satellite tags) outcomes of fishing stress on 5 species of coastal sharks (great hammerhead,
bull, blacktip, lemon, and tiger). Species-specific differences were detected in whole blood
lactate, partial pressure of carbon dioxide, and pH values, with lactate emerging as the sole
parameter to be significantly affected by increasing hooking duration and shark size. Species-specific
differences in reflex impairment were also found; however, we did not detect any significant
relationships between reflex impairment and hooking duration. Taken together, we ranked each
species according to degree of stress response, from most to least disturbed, as follows: hammerhead
shark > blacktip shark > bull shark > lemon shark > tiger shark. Satellite tagging data
revealed that nearly 100% of all tracked tiger sharks reported for at least 4 wk after release, which
was significantly higher than bull (74.1%) and great hammerhead (53.6%) sharks. We discuss
which mechanisms may lead to species-specific differences in sensitivity to fishing and suggest
that observed variation in responses may be influenced by ecological and evolutionary phenomena.
Moreover, our results show that certain species (i.e. hammerhead sharks in this study) are
inherently vulnerable to capture stress and mortality resulting from fisheries interactions and
should receive additional attention in future conservation strategies.
... of species that exemplifies these challenges during handling times are the hammerhead sharks (family Sphyrnidae) due to their low stress tolerance caused by a fast build-up of stress related metabolites [4]. Two of the more prominent species of this family are the great and scalloped hammerheads, Sphyrna mokarran and Sphyrna lewini. ...
... Over 90% of great and scalloped hammerheads had died before landing during a survey of the U.S. shark bottom longline fisheries [5]. In addition, great hammerheads were shown to have a 46% chance of dying up to 3 weeks after release, and their mortality was correlated with high lactate concentration after capture, i.e., a long fight time [4]. While the lethal concentration of lactate in other large sharks ranged between 16 and 20 mmol l −1 [6], great hammerheads were shown to reach this concentration in as little as 20 min fight time [4]. ...
... In addition, great hammerheads were shown to have a 46% chance of dying up to 3 weeks after release, and their mortality was correlated with high lactate concentration after capture, i.e., a long fight time [4]. While the lethal concentration of lactate in other large sharks ranged between 16 and 20 mmol l −1 [6], great hammerheads were shown to reach this concentration in as little as 20 min fight time [4]. However, great and scalloped hammerheads are listed as Critically Endangered on the IUCN red list [7,8] and both species would benefit from more fine-scale movement data, such as those generated by fin-mounted satellite-linked geolocators, allowing the discussion of more adequate conservation management measures [9]. ...
Fin-mounted geolocators are widely used in marine studies to track animal movements and to design informed management strategies. However, the deployment protocols of such geolocators, which normally consist of drilling one to multiple holes using a template, can be challenging, and depending on the animal’s stress physiology and ocean conditions, speed and accuracy may be crucial. Here, we present the plans for a drill attachment allowing the template-free drilling of up to four holes simultaneously for a faster, more accurate and safer deployment of fin-mounted geolocators. The drill attachment was successfully tested on four great and two scalloped hammerheads, Sphyrna mokarran and Sphyrna lewini, which were all tagged with 4-bolt Smart Position and Temperature (SPOT) tags. The time required to secure the geolocators, from drill alignment to the complete fastening of the last bolt, ranged from 68 to 85 s (78.2 ± 10.9 s, mean ± SD). The new drill attachment further allowed the successful tagging of a great hammerhead alongside a research vessel in rough seas that would have made the deployment using traditional protocols more challenging. Simultaneously drilling four holes reduces the need to keep the animal’s fin steady for an extended period of time and thus makes the deployment of fin-mounted geolocators less dependent on the animal’s behavior and the weather conditions. As such, the 4-hole drill attachment makes the mounting process faster and more reliable and should reduce the stress experienced by the animal.
... Catch-and-release can also occur on commercial fishing vessels where it has been estimated that ∼9.1 million tonnes of non-target fish per year globally are caught and released in commercial fisheries (Sepulveda et al., 2019;Gilman et al., 2020). Numerous studies have investigated the physiological and ecological impacts of catch-and-release fishing on teleosts and elasmobranchs (Cooke and Schramm, 2007;Cooke et al., 2013;Gale et al., 2013;Gallagher et al., 2014;Schlenker et al., 2016;Jerome et al., 2017;Gallagher et al., 2019;Sepulveda et al., 2019;Mohan et al., 2020). Catch-and-release fishing is considered a multi-stressor interaction for individuals (Gale et al., 2013), with the negative impacts broadly categorised as lethal or sub-lethal, with potential sub-lethal impacts including altered blood chemistry (Gallagher et al., 2014;Dapp et al., 2016), behavioural impairments (Raoult et al., 2019), reduced growth and reproductive rates and increased disease vulnerability (Gale et al., 2013). ...
... Numerous studies have investigated the physiological and ecological impacts of catch-and-release fishing on teleosts and elasmobranchs (Cooke and Schramm, 2007;Cooke et al., 2013;Gale et al., 2013;Gallagher et al., 2014;Schlenker et al., 2016;Jerome et al., 2017;Gallagher et al., 2019;Sepulveda et al., 2019;Mohan et al., 2020). Catch-and-release fishing is considered a multi-stressor interaction for individuals (Gale et al., 2013), with the negative impacts broadly categorised as lethal or sub-lethal, with potential sub-lethal impacts including altered blood chemistry (Gallagher et al., 2014;Dapp et al., 2016), behavioural impairments (Raoult et al., 2019), reduced growth and reproductive rates and increased disease vulnerability (Gale et al., 2013). Fish can experience oxygen deprivation (Schwieterman et al., 2021), handlingrelated injuries (Cooke et al., 2013;French et al., 2015) and heat stress (Wosnick et al., 2018(Wosnick et al., , 2019. ...
... In addition to altered thermal dynamics, hooked fish may undergo altered blood biochemistry as a result of the event (Gallagher et al., 2014;Dapp et al., 2016;Mohan et al., 2020;Schwieterman et al., 2021). Capture can often result in hyperkalemia, metabolic and respiratory acidosis (Schwieterman et al., 2021) and declines in blood oxygen concentration, as a result of the often exhaustive exercise and apneic asphyxia associated with capture (Schwieterman et al., 2021). ...
Catch-and-release fishing is an important component of ecotourism industries and scientific research worldwide, but its total impact on animal physiology, health and survival is understudied for many species of fishes, particularly sharks. We combined biologging and blood chemistry to explore how this fisheries interaction influenced the physiology of two widely distributed, highly migratory shark species: the blue shark (Prionace glauca) and the tiger shark (Galeocerdo cuvier). Nineteen sharks were caught by drum line or rod-and-reel angling; subcutaneous body temperature measurements were taken immediately upon capture, with six individuals also providing subsequent subcutaneous body temperature measurements via biologging as they swam freely for several hours post-release. We found that short-term capture caused shark body temperature to increase significantly and rapidly, with increases of 0.6°C–2.7°C for blue sharks (mean, 1.2 ± 0.6°C) and 0.5°C–0.9°C for tiger sharks (mean, 0.7 ± 0.2°C) and with capture-induced heating rates of blue sharks averaging 0.3°C min−1 but as high as 0.8°C min−1. Blue shark body temperature was even higher deeper into the white muscle. These heating rates were three to eight times faster than maximum rates encountered by our biologging sharks swimming through thermally stratified waters and faster than most acute heating experiments conducted with ectotherms in laboratory experiments. Biologging data showed that body temperatures underwent gradual decline after release, returning to match water temperatures 10–40 mins post-release. Blood biochemistry showed variable lactate/glucose levels following capture; however, these concentrations were not correlated with the magnitude of body temperature increase, nor with body size or hooking time. These perturbations of the natural state could have immediate and longer-term effects on the welfare and ecology of sharks caught in catch-and-release fisheries and we encourage further study of the broader implications of this reported phenomenon.
... All sharks were captured using standardized circle-hook drumlines, a passive, autonomous fishing technique, as described in Gallagher et al. (2014). The gear consisted of a submerged weight base tied to a line running to the surface by means of an attached, inflatable buoy float. ...
... To facilitate respiration, a hose was immediately inserted into the shark's mouth that actively pumped water over the shark's gills. This capture and handling method was selected to promote shark vitality and reduce stress levels during sampling, as previous stress analysis have shown that tiger sharks do not experience physiological stress using these procedures (Gallagher et al., 2014). ...
... In October 2013, May 2014 and November 2014, tiger sharks were caught in the study area using sets of drumlines with baited circle-hooks (described in Gallagher et al., 2014). Once caught, hooked sharks were secured alongside the boat where sex and length measurements (total length (TL) cm) were recorded and pregnancy status was assessed through imaging the reproductive tract of each female shark using ultrasonography (Ibex Pro portable ultrasound, EI Medical Imaging, Loveland, CO, U.S.A.), with a 60 mm curved linear array 2.5e5 MHz transducer (model 290470). ...
While a growing body of literature has shown that tourism provisioning can influence the behaviour of wildlife, how physiological state might be related to the nature and magnitude of these effects remains poorly understood. Physiological state, including reproductive and nutritional status, can have profound effects on an individual's behaviour and decision making. In the present study, we used multiple physiological markers related to reproductive (testosterone, 17β-oestradiol and progesterone), metabolic (corticosteroids) and nutritional ecology (stable isotopes and fatty acids), integrated with ultrasonography and passive acoustic telemetry to explore the possible relationship between physiological condition and space use of tiger sharks, Galeocerdo cuvier, exposed to dive tourism provisioning. Large, nongravid female tiger sharks, with higher plasma steroid levels (i.e. testosterone, 17β-oestradiol, relative corticosteroid), enriched δ¹⁵N and elevated nutritional status (in terms of fatty acids) spent proportionally more time at food provisioning sites compared to conspecifics. Testosterone levels also were positively correlated with the proportion of time spent at provisioning sites. Based on these results, we speculate that physiological condition plays a role in shaping the spatial behaviour of female tiger sharks within the context of food provisioning, whereby larger individuals, exhibiting higher testosterone levels and elevated nutritional status, show selective preferences for provisioning dive sites, where they outcompete conspecifics of relatively smaller size, lower testosterone levels and depressed nutritional state. While more studies are needed to explore whether sharks are making these decisions because of their physiological state or whether spending more time at provisioning sites results in altered physiological state, our findings highlight the importance of considering animal life stage, endocrine regulation, and nutritional condition when evaluating the biological impacts of provisioning tourism.
... Assuming the relationship between behavior and animal welfare becomes more clearly defined, our technique can help, in part, identify or address the efficacy of certain fishing best practices and gear modifications. For example, soak time reductions have been recommended to mitigate mortality (Diaz and Serafy, 2005;Campana et al., 2009;Morgan and Carlson, 2010;Gallagher et al., 2014). However, this best fishing practice may be less effective if the focal species completely exhausts itself shortly after being hooked, and acute physiological stress leads to DM (Gallagher et al., 2014). ...
... For example, soak time reductions have been recommended to mitigate mortality (Diaz and Serafy, 2005;Campana et al., 2009;Morgan and Carlson, 2010;Gallagher et al., 2014). However, this best fishing practice may be less effective if the focal species completely exhausts itself shortly after being hooked, and acute physiological stress leads to DM (Gallagher et al., 2014). Our technique can provide behavioral information to confirm this type of response to capture and interpret the efficacy of the practice if behaviors are also linked to animal health. ...
... Handlines were used as a proxy for pelagic longline gear; however, our technique could easily be adapted to other hook-and-line fisheries. This technique, for example, could be matched with drumlines as a proxy for capture in bottom longline fisheries (e.g., Gallagher et al., 2014Gallagher et al., , 2017 and used directly on terminal tackle to address rod-and-reel fisheries. It may also be possible to use a similar monitoring approach with gillnet gear, using appropriately placed accelerometers and cameras (e.g., attached to float lines). ...
Animal behavior varies in response to capture between/within species and fisheries, and its expression may contribute to incidental mortality when behaviors result in physiological ramifications that cannot be resolved. However, this relationship between capture behavior and animal health is poorly understood, and it remains a logistical challenge to evaluate behavior during capture. We describe an experimental technique that characterizes and quantifies capture behavior in hook-and-line fisheries. This technique includes (1) simultaneously monitoring the behavioral response to capture with accelerometers and cameras, (2) characterizing behavior from video footage and linking discrete behaviors to acceleration data, and (3) predicting behavior based solely on acceleration data using an ensemble of supervised classification methods. We captured oceanic whitetip sharks, Carcharhinus longimanus, with experimental (hook-and-line) gear to test these techniques (n = 38 capture events), with capture durations ranging from 4 to 68 min. In all, 145,589 tri-axial acceleration observations were collected across these events, including simultaneous video footage (six hours total) from 10 capture events. Three discrete capture behaviors were characterized: steady swimming, a high-energy response consisting of thrashing and burst swimming, and a loss of body orientation while hanging motionless from the gear. The latter two behaviors can lead to physiological stress if exhibited for prolonged periods. Our trained ensemble of supervised classification methods successfully predicted behaviors from acceleration data with up to 95.2% accuracy. This technique provides a better understanding of the behavioral response to hook-and-line capture and, if paired with health or fate assessments, can characterize the influence of behavior on mortality. Our technique also provides a method for predicting behavior based on acceleration data alone, which can be more feasible to collect across the spectrum of fishing conditions and practices within a fishery. Such information will assist in understanding how species respond to capture on hook-and-line gear and in the formulation of species-and fishery-specific strategies for mitigating mortality.
... In addition, body length may affect survival, as in some species large individuals exhibit higher tolerance to hooking trauma (Campana et al. 2009). Sea temperature can be another significant variable, potentially having a positive or negative effect on capture and (or) survival rates depending on the species (Bromhead et al. 2012;Gallagher et al. 2014b). Finally, soak duration (the length of time the longline remains in the water) can be an important factor impacting AVM, as has been shown for the blue shark (Prionace glauca) (Diaz and Serafy 2005). ...
... Our results add to these findings, indicating that hooking temperature and body size have combined effects on the consequences of the stress endured by the individual. Gallagher et al. (2014b) showed a significant negative relationship between the size of some shark species and the lactate concentration in the blood, the latter also being correlated with mortality for the blue shark (Moyes et al. 2006). The lactate concentration in the blood can be linked to "fighting time" on the line (Gallagher et al. 2014b;Jerome et al. 2018). ...
... Gallagher et al. (2014b) showed a significant negative relationship between the size of some shark species and the lactate concentration in the blood, the latter also being correlated with mortality for the blue shark (Moyes et al. 2006). The lactate concentration in the blood can be linked to "fighting time" on the line (Gallagher et al. 2014b;Jerome et al. 2018). ...
Elasmobranchs make up a significant part of bycatch in pelagic longline fisheries, whose induced mortality can be a major threat to endangered species. It is therefore crucial to understand the drivers of at-vessel mortality (AVM) for this fishing gear in order to enhance post-release survival. To this end, we analysed scientific data collected during monitored longline fishing experiments conducted in French Polynesia to (i) estimate AVM for each species based on bootstrapped samples, and (ii) to assess AVM drivers using multivariate logistic regression models for the blue shark (Prionace glauca) and oceanic whitetip shark (Carcharhinus longimanus). We found that AVM varies widely between species. Oceanic whitetip sharks are more likely to die when caught in waters outside their comfort temperature range, and their odds of survival increase with body length. For the blue shark, the only driver related to AVM is hooking duration. These results indicate that to reduce AVM of these two species, the vertical distribution of hooks and soak duration should be considered as mitigation measures related to pelagic longlining.
... Investigations into the physiological and behavioral impacts of fisheries interactions on sharks are increasing in frequency, and over time have increased our body of knowledge on a species, region, and fisheries-specific basis (Dapp et al., 2017;Gallagher et al., 2014a;Guida et al., 2016;Jerome et al., 2018). Capture stress in sharks has most commonly been measured through blood-based biomarkers such as pH, glucose, lactate, and plasma electrolytes (e.g., K+, Ca 2+ , PO 4 3 ) (Cliff and Thurman, 1984;Gallagher et al., 2014a;Mandelman and Skomal, 2009;Skomal, 2006;Wedemeyer and Yasutake, 1977;Wells et al., 1986). ...
... Investigations into the physiological and behavioral impacts of fisheries interactions on sharks are increasing in frequency, and over time have increased our body of knowledge on a species, region, and fisheries-specific basis (Dapp et al., 2017;Gallagher et al., 2014a;Guida et al., 2016;Jerome et al., 2018). Capture stress in sharks has most commonly been measured through blood-based biomarkers such as pH, glucose, lactate, and plasma electrolytes (e.g., K+, Ca 2+ , PO 4 3 ) (Cliff and Thurman, 1984;Gallagher et al., 2014a;Mandelman and Skomal, 2009;Skomal, 2006;Wedemeyer and Yasutake, 1977;Wells et al., 1986). Whereas the majority of shark species assessed have been those commonly encountered in longline bycatch (e.g., Butcher et al., 2015;Gallagher et al., 2014b), in recent years there has been a focus on triaging species of emerging conservation concern including assessments of IUCN Red List Threatened species (e.g., smalltooth sawfish, Pristis pectinata; Prohaska et al., 2018), as well as CITES-listed species (e. g., white shark, Carcharodon carcharias; Gallagher et al., 2019). ...
... We used generalized linear models (GLMs) to evaluate the potential influence of HT, sea surface temperature (SST), and TL on glucose, lactate, pH, Ca 2+ , PO 4 3-, and K + (Dapp et al., 2017;Gallagher et al., 2014a;Jerome et al., 2018). We first assessed potential collinearity among independent variables using the R package usdm (Naimi et al., 2014). ...
Sharks, like other fish, react to capture and handling stress with more exaggerated physiological responses than most other vertebrates, and the potential consequences of their capture include both sub-lethal and lethal effects. Blue sharks, Prionace glauca, are one of the most heavily exploited species of sharks in the world, both in commercial and recreational fisheries, and while the capture response of blue sharks in commercial fisheries has been comparably well-studied, there is a relative lack of information regarding the influence of handling and capture on the species in the recreational setting. Our analysis of blood-based biomarkers, such as glucose, lactate, pH, and plasma electrolytes, sampled from twenty blue sharks captured in the recreational fishery suggests that over the short hook times (time on the line) characteristic of the fishery, blue sharks do not fight to the point of blood acidosis and are likely able to withstand capture and handling in a catch-and-release setting. We did note an inverse relationship between shark total length and blood glucose levels, suggesting the possibility that smaller individuals may be more susceptible to capture stress, but this variation may also reflect other metabolic factors or an ontogenetic shift in diet. We discuss these findings within the context of the recreational fishery, including priorities for angler education.
... Pure biologging objectives usually focus on examining natural behavior, but this requires accounting for behavioral disturbances resulting from the tagging process, including capture and handling which are often necessitated for deployments on elusive or transient species, or due to tag application requirements (e.g., rigid attachment/careful alignment for accelerometers/magnetometers; Wilson et al., 2008;Shillinger et al., 2012; but see Chapple et al., 2015;Pearson et al., 2017). The magnitude, nature and duration of post-release disturbance can vary between individuals, species and contexts (e.g., capture behavior, environmental conditions; Gallagher et al., 2014;Guida et al., 2016;Whitney et al., 2016), yet these responses are often excluded from detailed analysis as unwanted side-effects to natural behavior (e.g., Coffey et al., 2020). Conversely, understanding animals' responses to and recovery from human disturbance is a key aim of applied behavioral research, for which comprehensive knowledge of natural behavior is also required as a reference point (Walker, 1998;Wilson et al., 2014). ...
... Supporting this explanation, offshore dispersal of white sharks coincided with a period of faster tailbeats (i.e., rapid movement), which gradually slowed to a more constant average rate, indicating a population-level recovery period (return to "baseline" tailbeat signature) of 9.7 h. This pattern and rate of TBC recovery is similar to that identified for common blacktip sharks (Carcharhinus limbatus, 9 h;Whitney et al., 2016), but longer than for tiger sharks (Galeocerdo cuvier, 4 h; Andrzejaczek et al., 2019a), potentially suggesting lower sensitivity to capture in tiger sharks (consistent with Gallagher et al., 2014). Activity level metrics such as TBC are clearly useful for enabling standardized comparisons of recovery rates both between and within species (Brivio et al., 2015;Whitney et al., 2016;Shuert et al., 2021), yet such applications amongst elasmobranchs remain rare or are limited by short post-release monitoring periods (Bullock et al., 2015;Whitney et al., 2018;Raoult et al., 2019). ...
... Despite a low sample size, we also revealed that recovery times increased as shark length decreased. Although physiological stress responses to capture (e.g., lactate accumulation) are known to be magnified in smaller individuals for some shark species, which can influence postrelease outcomes (Gallagher et al., 2014;Talwar et al., 2017;Bowlby et al., 2021), white sharks across a range of sizes are quite physiologically resilient to short captures (<75 min, as per our study; Gallagher et al., 2019;Tate et al., 2019). Therefore, other factors (e.g., size-specific personalities) may underlie the 10-fold variance in behavioral recovery (∼3-30 h) we observed across sizes. ...
Multisensor biologging provides a powerful tool for ecological research, enabling fine-scale observation of animals to directly link physiology and movement to behavior across ecological contexts. However, applied research into behavioral disturbance and recovery following human interventions (e.g., capture and translocation) has mostly relied on coarse location-based tracking or unidimensional approaches (e.g., dive profiles and activity/energetic metrics) that may not resolve behaviors and recovery processes. Biologging can improve insights into both disturbed and natural behavior, which is critical for management and conservation initiatives, although challenges remain in objectively identifying distinct behavioral modes from complex multisensor datasets. Using white sharks ( Carcharodon carcharias ) released from a non-lethal catch-and-release shark bite mitigation program, we explored how combining multisensor biologging (video, depth, accelerometers, gyroscopes, and magnetometers), track reconstruction and behavioral state modeling using hidden Markov models (HMMs) can improve our understanding of behavioral processes and recovery. Biologging tags were deployed on eight white sharks, recording their continuous behaviors, movements, and environmental context (habitat, interactions with other organisms/objects) for periods of 10–87 h post-release. Dive profiles and tailbeat analysis (as a standard, activity-based method for assessing recovery) indicated an immediate “disturbed” period of offshore movement, displaying rapid tailbeats and an average tailbeat-derived recovery period of 9.7 h, with evidence of smaller individuals having longer recoveries. However, further integrating magnetometer-derived headings, track reconstruction and HMM modeling revealed a cryptic shift to diurnal clockwise-counterclockwise circling behavior, which we argue represents compelling new evidence for hypothesized unihemispheric sleep amongst elasmobranchs. By simultaneously providing critical information toward conservation-focused shark management and understudied aspects of shark behavior, our study highlights how integrating multisensor information through HMMs can improve our understanding of both post-release and natural behavior, especially in species that are difficult to observe directly.
... Despite being prohibited and a careful monitoring of the quota, assessments have shown that they are still overfished, and that commercial discards average~78 metric tons [49]. Blacktip sharks are the second most commonly caught species in this fishery [50] and, based on their blood stress values, are thought to be more susceptible to post-release mortality than other species [37,39,40]. Several recent studies have examined their PRM in recreational fisheries [17,27,44,45,51] but none have done so in a BLL fishery. ...
... Few published studies have assessed PRM rates in tiger, bull, blacktip, or spinner sharks following fisheries interactions. However, our finding of a 2.0% PRM rate in tiger sharks is similar to estimates from drumline fishing methods in the NW Atlantic (n = 28 [39]) and bottom longline gear in the SW Atlantic (n = 21 [15]), where no capture-related mortality was reported in tiger sharks. The estimate of 26% PRM reported for bull sharks on drumline gear in the NW Atlantic (n = 27 [39]) is over three times as high as our study, although this previous estimate was based on reporting rates of fin-mounted satellite tags and may overestimate mortality if tag failure or shark behavior prevent satellite transmissions. ...
... However, our finding of a 2.0% PRM rate in tiger sharks is similar to estimates from drumline fishing methods in the NW Atlantic (n = 28 [39]) and bottom longline gear in the SW Atlantic (n = 21 [15]), where no capture-related mortality was reported in tiger sharks. The estimate of 26% PRM reported for bull sharks on drumline gear in the NW Atlantic (n = 27 [39]) is over three times as high as our study, although this previous estimate was based on reporting rates of fin-mounted satellite tags and may overestimate mortality if tag failure or shark behavior prevent satellite transmissions. In blacktip sharks, PRM rates have previously been estimated at 9-23% in recreational fisheries [17,27,44], and we found substantially higher PRM for this species in the BLL fishery. ...
Bycatch mortality is a major factor contributing to shark population declines. Post-release mortality (PRM) is particularly difficult to quantify, limiting the accuracy of stock assessments. We paired blood-stress physiology with animal-borne accelerometers to quantify PRM rates of sharks caught in a commercial bottom longline fishery. Blood was sampled from the same individuals that were tagged, providing direct correlation between stress physiology and animal fate for sandbar ( Carcharhinus plumbeus , N = 130), blacktip ( C . limbatus , N = 105), tiger ( Galeocerdo cuvier , N = 52), spinner ( C . brevipinna , N = 14), and bull sharks ( C . leucas , N = 14). PRM rates ranged from 2% and 3% PRM in tiger and sandbar sharks to 42% and 71% PRM in blacktip and spinner sharks, respectively. Decision trees based on blood values predicted mortality with >67% accuracy in blacktip and spinner sharks, and >99% accuracy in sandbar sharks. Ninety percent of PRM occurred within 5 h after release and 59% within 2 h. Blood physiology indicated that PRM was primarily associated with acidosis and increases in plasma potassium levels. Total fishing mortality reached 62% for blacktip and 89% for spinner sharks, which may be under-estimates given that some soak times were shortened to focus on PRM. Our findings suggest that no-take regulations may be beneficial for sandbar, tiger, and bull sharks, but less effective for more susceptible species such as blacktip and spinner sharks.
... Based on our second research question, results also indicate that I. oxyrhynchus is more vulnerable to mortality due to capture stress than other Carcharhiniformes. To date, hammerhead sharks are considered the most sensitive to the negative effects of capture, exhibiting consistently high stress marker levels coupled with the highest mortality rates among studied sharks (Gallagher et al., 2014b;Butcher et al., 2015;Gulak et al., 2015;Jerome et al., 2018). It is believed that their evolutionary history is in part responsible for such vulnerability, as their extreme morphological alterations (i.e., cephalofoil) make them less resistant to stressors (Gallagher et al., 2014a). ...
... In this regard, circulating lactate levels were higher in Daggernose sharks when compared to both Carcharhinus spp. and Sphyrna spp., although concentrations were also very elevated in the latter, consistent with previous studies (Gallagher et al., 2014b;Jerome et al., 2018). Lactate is the most reliable stress marker for elasmobranchs (Skomal and Mandelman, 2012), being consistently high in stressed animals as a byproduct of anaerobic metabolism due to strenuous exercise (Skomal and Bernal, 2010;Wosnick et al., 2017;Jerome et al., 2018). ...
The current Isogomphodon oxyrhynchus (Daggernose Shark) population status points to 99% losses in the last decade due to certain biological traits, site fidelity, and historical high representativeness as bycatch in artisanal fisheries. This species is listed as Critically Endangered (CR), both in the IUCN and the Brazilian Red Lists. Its vulnerability is so high that its recovery potential requires protection from ongoing fishing pressure.
In this context, this study aimed to evaluate the health status of Daggernose sharks and their ability to cope with allostatic overload in a comparative analysis with other Carcharhinid and Sphyrnid sharks. Sharks incidentally caught by the artisanal fleet in the state of Maranhão, on the Brazilian Amazon Coast, were sampled for blood, and serum was used to assess biochemical markers. The findings indicate significant differences in Daggernose Shark homeostatic capacity for ALP, ALT/GTP, creatinine, lactate, urea, total cholesterol, and triglycerides, pointing to lower health scores and recovery capacity when compared to other Carcharhiniformes inhabiting the same region.
It is possible that such vulnerability is a result of fisheries-induced evolution, leading to remaining populations with very low chances of fully recovering. Conservation planning is thus urgent, as current legislation based on fishing bans does very little for the species. International collaboration and longterm recovery measures are necessary, including the creation of MPAs specially designed for the species and captive maintenance aiming to monitor health status and carry out breeding attempts.
... Ecological knowledge on hammerhead sharks mainly originates from the studies carried out on great and scalloped hammerheads (Gallagher et al., 2014a;. The two species are recognized as among the most sensitive shark species to fishing pressure (Gallagher et al., 2014b), due to unique ecological, behavioral and functional specializations. Large hammerheads are easy to catch and highly harvested, mostly for their fins . ...
... These two species are highly sensitive to fishing pressure due to their unique ecological (i.e., slow growth, late sexual maturity, low reproductive rate, relatively low number of offspring), functional (i.e., increase in physiological disturbances following catch resulting in high mortality rates even if the sharks are released post-capture) and behavioral (i.e., schooling, alternation between coastal and pelagic habitats) specificities (Gallagher et al., 2014a(Gallagher et al., , 2014b. The present study suggests that smooth hammerhead sharks share one of these behavioral traits, with long periods of coastal residency increasing vulnerability to fisheries in the Pacific coast of Mexico. ...
Characterizing the trophic ecology of sharks is fundamental to understand the potential cascading effects of their current décline in marine ecosystems. This thesis investigates the trophic niches of shark species in Coastal and offshore ecosystems around Baja California Sur (Mexico) in both the Pacific Ocean and the Gulf of California, a region characterized by a strong pressure from artisanal fisheries. Ecologically, the guiding thread was to elucidate the importance of resource partitioning in shaping shark realized trophic niches, at both the intra- and inter-specific level. To achieve this objective, multiple trophic biomarkers were used, such as carbon, nitrogen and mercury stable isotopes, and fatty acid compositions, to describe the vertical and horizontal dimensions of shark foraging habits.At the intra-specific level, resource partitioning was supported by the use of distinct ecosystems for juvenile hammerhead sharks due to ontogenetic shifts in habitat and prey. Inter-specific resource partitioning seems to be driven by foraging at different depth within pelagic assemblages, but could also depend on local environmental conditions, such as upwelling activity. This work also characterized the life cycle of a poorly studied hammerhead species, the smooth hammerhead shark (Sphyrna zygaena). The prolonged Coastal residency of this species through ontogeny suggests significant vulnerability to local artisanal fisheries. Finallly, the demonstrated complementarity of trophic markers provides a promising insight to unravel food web structure and ecological mechanisms.
... Increased mortality of marine fauna is often associated with set fishing gear (Butcher et al., 2015;Hutchinson et al., 2015;Sumpton et al., 2011). Although most species caught in this study have a high tolerance to capture stress (Gallagher et al., 2014(Gallagher et al., , 2019Tate et al., 2019), common blacktips and hammerhead sharks are inherently vulnerable to capture stress and display higher mortality rates (Butcher et al., 2015;Gallagher et al., 2014;Tate et al., 2019). While mortality rates were low, maintaining short response times is vital, particularly in programs like the NSW Shark Management Strategy, which aims to release animals alive and in good condition. ...
... Increased mortality of marine fauna is often associated with set fishing gear (Butcher et al., 2015;Hutchinson et al., 2015;Sumpton et al., 2011). Although most species caught in this study have a high tolerance to capture stress (Gallagher et al., 2014(Gallagher et al., , 2019Tate et al., 2019), common blacktips and hammerhead sharks are inherently vulnerable to capture stress and display higher mortality rates (Butcher et al., 2015;Gallagher et al., 2014;Tate et al., 2019). While mortality rates were low, maintaining short response times is vital, particularly in programs like the NSW Shark Management Strategy, which aims to release animals alive and in good condition. ...
There is increasing support for shark bite mitigation measures, such as SMART (Shark-Management-Alert-in-Real-Time) drumlines that minimise impacts on target sharks and other marine animals. On the east coast of Australia, SMART drumlines are used in a shark management program to catch and relocate white (Carcharodon carcharias), tiger (Galeocerdo cuvier), and bull sharks (Carcharhinus leucas; herein referred to as target sharks). This study examines the effect of bait position relative to the seabed on SMART drumline catches in eastern Australian waters, aiming to optimise catches of target sharks while reducing bycatch. Over 17 months, SMART drumlines were deployed at Ballina and Evans Head, New South Wales. Trace extensions were attached to 3.2 m standard traces to test the effect of bait height above the seabed on shark catch in an experimental design that alternated bait position every fortnight. White and tiger shark catches accounted for 67% of the total catch, whereas bull sharks were infrequently caught (3%). Bait position above the seabed did not significantly influence catch probability of white and tiger sharks. However, catches of Critically Endangered grey nurse sharks (Carcharias taurus) and false alarm events significantly increased when baits were closer to the seabed. Catches of white and tiger sharks varied throughout the year and were linked to seasonal water temperature changes. The standard traces effectively caught target shark species whilst reducing catches of grey nurse sharks and false alarm events, highlighting that the trace length currently used for NSW SMART drumline deployments is optimal.
... Great hammerheads were tagged via an externally tethered tag package, which used a dart anchor that was embedded in the shark's dorsal musculature. External tags were attached to great hammerheads because it allowed for faster attachment, considering this species' inherent sensitivity to capture and handling stress (Gallagher et al. 2014b, Jerome et al. 2018. While tag shedding is more likely with external transmitters (N. ...
... Notably, high use of urban-impacted sites exposes sharks to increased vulnerability from land-and boat-based angling in the region (Shiffman & Hammerschlag 2014, Shiffman et al. 2017. While sharks in Florida are often caught and released for sport, great hammerhead sharks exhibit a pronounced capture stress response and are vulnerable to post-release mortality (Gallagher et al. 2014b, Jerome et al. 2018). Sharks exposed to urbanization are also exposed to poor water quality and chemical pollution that could have health and immunological consequences. ...
Understanding and ultimately predicting how marine organisms will respond to urbanization is central for effective wildlife conservation and management in the Anthropocene. Sharks are upper trophic level predators in virtually all marine environments, but if and how their behaviors are influenced by coastal urbanization remains understudied. Here, we examined space use and residency patterns of 14 great hammerheads Sphyrna mokarran , 13 bull sharks Carcharhinus leucas , and 25 nurse sharks Ginglymostoma cirratum in proximity to the coastal metropolis of Miami, Florida, using passive acoustic telemetry. Based on the terrestrial urban carnivore literature, we predicted sharks would exhibit avoidance behaviors of areas close to Miami, with residency patterns in these urban areas increasing during periods of lower human activity, such as during nocturnal hours and weekdays, and that dietary specialists (great hammerhead) would exhibit comparatively lower affinity towards highly urbanized areas relative to dietary generalists (bull and nurse shark). However, we did not find empirical support for these predictions. Space use patterns of tracked sharks were consistent with that of ‘urban adapters’ (species that exhibit partial use of urban areas). Modeling also revealed that an unmeasured spatial variable was driving considerable shark residency in areas exposed to high urbanization. We propose several hypotheses that could explain our findings, including food provisioning from shore-based activities that could be attracting sharks to urban areas. Ultimately, the lack of avoidance of urban areas by sharks documented here, as compared to terrestrial carnivores, should motivate future research in the growing field of urban ecology.
... Sampling occurred during wet season (November -Abril) from 2011 to 2018 as part of ongoing coastal shark surveys (see Tinari and Hammerschlag, 2021). All sharks were captured using circle-hook drumlines, a minimally invasive technique that allows the captured sharks to swim (Gallagher et al., 2014). In brief, drumlines were deployed (10-40 m deep) to soak for 1 h before being checked for shark presence. ...
... Science of the Total Environment 826 (2022) 154082 fresh seawater was inserted into the shark's mouth to actively pump water (94.5 L per minute) over the shark's gills while temporarily immobilized. While sharks were secured, sex was recorded, various length and span measurements were taken, and blood samples were obtained; sharks were then tagged for identification and released (Gallagher et al., 2014). Blood (~10 mL) was collected from the caudal vein. ...
The synergistic effects of coastal urbanization have dramatically impacted biological communities. Yet, few studies have investigated how urbanization can influence the diet quality and trophic ecology of coastal sharks. In a preliminary study, we examined for spatial variation in the nutritional ecology of a highly active marine predator, the blacktip sharks (Carcharhinus limbatus) exposed to regional differences in coastal urbanization in southeast Florida. We used medium-term nutritional indicators (i.e., body condition; whole blood stable isotopes [δ¹⁵N and δ¹³C]) and short-term dietary markers (i.e., plasma fatty acid profiles) to test the hypothesis that the nutritional ecology of marine predators would differ in areas exposed to increased urbanization. Our initial results showed that blacktip sharks sampled in high urbanized area (hereafter, ‘urban sharks’) exhibited relatively higher body condition, blood δ¹⁵N levels, and percentages of saturated fatty acids compared to sharks sampled in low urbanized area (hereafter ‘non-urban sharks’). Collectively, these results suggest a possible positive alteration in the amount of food consumed by sharks and/or in the caloric value of their prey. We also found lower percentages of bacterial markers and higher values of dinoflagellate markers in urban sharks. Compared to more resident species evaluated in the region, we did not detect a reduction in diet quality (in terms of essential fatty acids) in this highly active species exposed to urbanization. Therefore, it is possible that the lifestyle and feeding behavior have an influence on the quality of food consumed by urban sharks, and maybe the impacts of urbanization are more pronounced in resident, sedentary and benthic species.
... Carcharhinus limbatus individuals were captured off the coast of southern FL (Fig. 1) throughout the year, from 2012 to 2017, by the University of Miami's Shark Research and Conservation Program (Miami, FL, US) as part of a longterm monitoring study (Tinari and Hammerschlag 2021), by using drumline fishing methods described in Gallagher et al. (2014). Each individual was sexed and measured for total length (TL). ...
... Individuals were assumed mature at TL greater than or equal to 145 cm for males and 155 cm for females (Branstetter 1987;Carlson et al. 2006). Up to 10 mL of blood was sampled from individuals by caudal venipuncture with 18-gauge needles and plastic non-heparinised syringes (Gallagher et al. 2014). Whole blood samples were centrifuged at 1300g for 5 min to separate the serum, which was then frozen at −20°C and shipped overnight on ice to the University of New England's Marine Science Center (Biddeford, ME, US). ...
Accurate reproductive information is crucial for the effective management of sharks. Here, we used non-lethal methods to evaluate reproductive hormone profiles of blacktip sharks (Carcharhinus limbatus) off the coast of southern Florida (FL) as part of a preliminary investigation of this species' reproductive patterns in the region. Circulating testosterone concentrations in males ranged from 0.04 to 320.7 ng mL −1 , and concentrations peaked during months previously shown to represent peak spermatogenic activity. In females, circulating concentrations of oestradiol (E2) ranged from 12.5 to 941.4 pg mL −1 , and progesterone (P4) ranged from 30.1 to 821.2 pg mL −1. E2 peaked during months with peak vitellogenic and ovulatory activity in previous studies; P4 displayed less variability among months. In general, changes in monthly hormone concentrations align well with the timing of reproductive events in C. limbatus in other regions. However, because of low monthly sample sizes and a lack of reproductive status confirmation, the female profiles raise interesting questions about this population's reproductive cycle that could be explored in future studies. Additional studies should collect larger monthly samples and incorporate supplementary data to provide more insight into the reproductive cycle of this species in southern FL.
... Scientists project that many HMS will shift their ranges poleward in response to climate-driven changes to the ocean environment (Monllor-Hurtado et al., 2017) and that some, particularly in equatorial areas, will experience changes to their abundances (decreases for swordfish (Erauskin-Extramiana et al., 2020) and increases for yellowfin and skipjack tuna, except in the Western Central Equatorial Pacific (Erauskin-Extramiana et al., 2019)). Several HMS are particularly affected by low oxygen levels, and scientists project that climate change will potentially make survival more difficult for many HMS, especially after being released alive from fishing gear (Dapp et al., 2016;Dell'Apa et al., 2018;Gallagher et al., 2014a). In some coastal and marine regions around the globe, oxygen-rich layers of water will become shallower, driving some species to the surface where they will become more vulnerable to fishing gear (Prince & Goodyear, 2006;Stramma et al., 2012;Vedor et al., 2021). ...
... As with tunas and billfishes, pelagic sharks are vulnerable to higher metabolic stress and thus higher post-release mortality under reduced DO conditions (Carlson & Parson, 2001;Schlaff et al., 2014). Hammerhead sharks are among the most vulnerable to capture stress and post-release mortality (Gallagher et al., 2014a), whereas blue sharks tend to have lower at-vessel mortality rates (Campana et al., 2016), particularly when caught in deeper waters (Gallagher 2014b). However, the vertical distribution of blue sharks is also affected by DO-based habitat compression (i.e., OMZ shoaling) in the tropical East Atlantic (Vedor et al. 2021), similar to the scenario described above for istiophorid billfishes (Prince et al., 2010;Stramma et al., 2012), which will make this species more susceptible to interactions with pelagic longline fishing gear at the surface in this region. ...
This report examines the effects of climate change on highly migratory pelagic species (HMS), including tunas, swordfish, istiophorid billfishes, and sharks, in the North Atlantic and the implications for HMS fisheries in the United States.
... Sharks were captured using a series of baited drumlines, as described in Gallagher et al. (2014). Captured sharks were either secured alongside a boat in the water or on top of a floatable platform, in preparation for electronic tagging. ...
... C. leucas and G. cirratum were tagged via surgical implantation into the shark's body cavity following the approach of Hammerschlag et al. (2017), whereas S. mokarran were tagged via an externally tethered tag package, which used a dart anchor that was embedded in the shark's dorsal musculature. The external tag approach was used for great hammerheads because it allowed for faster tag attachment, considering this species' inherent sensitivity to capture and handling stress (Gallagher et al., 2014;Jerome et al., 2018). While tag shedding is more likely with external transmitters, this risk was minimized by looping the tag tether through the dorsal fin prior to insertion in the dorsal musculature. ...
Aquatic ecosystems face numerous anthropogenic threats associated with coastal urbanization, with boat activity being among the most prevalent. The present study aimed to evaluate a potential relationship between boat activity and shark space use in Biscayne Bay, Florida (USA), a coastal waterway exposed to high levels of boating. Spatiotemporal patterns in boat density and traffic were determined from aerial surveys and underwater acoustic recorders, respectively. These data were then compared with residency patterns of bull (Carcharhinus leucas), nurse (Ginglymostoma cirratum) and great hammerhead (Sphyrna mokarran) sharks quantified through passive acoustic telemetry. Results were mixed, with no detectable relationship between boat density and shark residency for any of the species. Hourly presence of G. cirratum decreased with increasing boat traffic, a relationship not seen in the other two species. Explanations for these results include habituation of sharks to the high levels of chronic boat activity in the study area and interspecific differences in hearing sensitivity.
... Capture-stress is well studied in several species (e.g. Hoffmayer & Parsons, 2001;Mandelman & Skomal, 2009;Lambert et al., 2018;Marshall et al., 2012;Gallagher et al., 2014;Wosnick et al., 2017a). However, capture-stress studies rarely differentiate effects for each sex, with exceptions noted for some endocrine and seasonal studies (Manire et al., 2007;Hoffmayer et al., 2012;Guida et al., 2017). ...
... Lactate, potassium and phosphorus were all elevated in dead animals during the reproductive period, corroborating their use as stress markers for Shortnose guitarfish males, as previously validated for females (Wosnick et al., 2018). The increases in lactate levels in dead animals are expected, due to respiratory and metabolic acidosis (Hoffmayer & Parsons, 2001;Mandelman & Farrington, 2007;Frick et al., 2010;Brooks et al., 2012;Gallagher et al., 2014;Wosnick et al., 2017a). The increases in potassium concentrations observed in dead animals are also expected due to cell lysis and is a reliable indicator of allostatic overload (e.g. ...
The assessment of physiological responses to capture provides useful information for elasmobranch conservation. In particular, understanding these impacts in species caught as bycatch that are released after capture can predict their “post‐release” fate and aid in management plans. Although well studied in several species, capture‐stress is nonetheless frequently assessed without considering putative variability between sexes. Given the high mortality of pregnant Zapteryx brevirostris females reported in the literature, the present study aimed at determining greatest vulnerability period for males. Our results demonstrate that, when caught during the reproductive period, males display higher mortality (68%) than when caught outside the reproductive period (zero mortality). Seven out of 11 markers (i.e. sodium, chloride, potassium, lactate, phosphorus, triglycerides and condition factor) differed significantly following capture‐induced stress between males caught during the reproductive period and those caught outside this period. Taken together, these results demonstrate the need for specific protocols during the reproductive period, to improve Shortnose guitarfish management and conservation.
... In the southwestern Pacific region, a previous study using commercial fishing records and research trawl surveys estimated that the species inhabits shallow coastal areas for about 2 years based on individuals fishing location and age determination (Francis, 2016). schooling, alternation between coastal and pelagic habitats) specificities (Braccini et al., 2022;Gallagher, Serafy, et al., 2014). The present study suggests that smooth hammerhead sharks share one of these behavioural traitslong periods of coastal residency, which increase the vulnerability to artisanal fisheries accounting for the majority of the shark captures in the Pacific coast of Mexico (Cartamil et al., 2011;Ramírez-Amaro et al., 2013). ...
1. The management of migratory taxa relies on the knowledge of their movements. Among them, ontogenetic habitat shift, from nurseries to adult habitats, is a behavioral trait shared across marine taxa allowing resource partitioning between life stages and reducing predation risk. As this movement is consistent over time, characterizing its timing is critical to implement efficient management plans, notably in coastal areas to mitigate the impact of fisheries on juvenile stocks. 2. In the Mexican Pacific, habitat use of the smooth hammerhead shark (Sphyrna zygaena) is poorly described, while the species is heavily harvested. Given the large uncertainties associated with the timing of out‐migration from coastal nursery grounds to offshore waters prior to reproductive maturity, a more precise assessment of smooth hammerhead shark movements is needed. 3. Photochemical degradation of mercury imparts mass‐independent isotope fractionation (Δ199Hg) which can be used to discriminate between neonate coastal shallow habitats and the offshore deep foraging patterns of late juveniles. Here, we present the application of muscle Δ199Hg as molecular clocks to predict the timing of ontogenetic habitat shifts by smooth hammerhead sharks, based on their isotopic compositions at the initial and arrival habitats and on muscle isotopic turnover rate. 4. We observed decreases in Δ199Hg values with shark body length, reflecting increasing reliance on offshore mesopelagic prey with age. Coastal residency estimates indicated that smooth hammerhead sharks utilize coastal resources for two years prior to offshore migration, suggesting a prolonged residency in these ecosystems. 5. Policy implications: This study demonstrates how mercury stable isotopes and isotopic clocks can be implemented as a complementary tool for stock management by predicting the timing of animal migration—a key aspect in the conservation of marine taxa. In the Mexican Pacific, fishing pressure on shark species occurs in coastal habitats depleting juvenile stocks. Consequently, management decision support tools are imperative for effectively maintaining early life stage population levels over time. The finding that smooth hammerhead sharks extensively rely on highly fished habitats for two years after parturition supports the relevance of establishing a size limit in coastal fisheries and demonstrates how the current temporal shark fishing closure could lack efficiency for the species.
... Independientemente de las medidas de gestión implementadas, se debe disponer de datos precisos sobre las capturas incidentales de tiburones ETP (además de marrajo azul) si se quiere reducir efectivamente las interacciones con los artes de pesca en el futuro, especialmente porque las prohibiciones de retención a bordo no logran reducir eficientemente la mortalidad (Gallagher et al., 2014a(Gallagher et al., , 2014b. ...
In the present work, key aspects of the biology and ecology of the shortfin mako were studied. Feeding habits, analysed in two ocean basins, indicated that pelagic fish and cephalopods were the main prey items. In the South Pacific Ocean, a marked sexual segregation was found, with females being more common in the SE region; this was also the area with a higher abundance of juveniles and of late-stage pregnant females. In the North Atlantic Ocean, large-scale horizontal movements (including trans-Atlantic migrations) were identified and diel vertical behaviour patterns described. Importantly, individuals that performed wider movements away from the tagging location were less at risk from surface longline fishing. Using tagging and recapture data that spanned a ten-year period, survival, dispersal, and fishing mortality rates for both mako and blue sharks were estimated. The presence of plastics and hooks was also observed for both species, in two studied ocean basins. Finally, bycatch rates for other internationally protected shark species that are commonly caught using surface longlines was estimated based on direct observations, which were several times higher than the official reported data. The results presented here are especially relevant for improving the management measures focused on pelagic sharks.
... Similarly, fish caught and tagged on commercial longline vessels have reduced survival the longer the time-period is between hooking and retrieval [61,71,73]. Disruption of physiological homeostasis associated with capture is also common in fishes (e.g., [35,60,94]). For example, elevated plasma cortisol, lactate, and plasma ion levels have been recorded as are common when times from hooking to sampling (i.e., "fight times") exceeded 10 min (e.g., [53,58,90]). ...
Archival (data-storage) and telemetry (acoustic and radio) tags are commonly used to provide data on the behavior and physiology of organisms, as well as data on their surrounding environment. For fishes, it is often advantageous to implant tags in the peritoneal cavity (i.e., intracoelomic implantation). The literature on best practices is limited for marine species, and near absent for tunas despite their regular application. We identify recommended practices using laparotomy in tropical tuna species following observations from thousands of tags implantations undertaken during implementation of several tagging programs across the Pacific. These recommended practices include descriptions of preferred tagging stations and equipment, fish selection, surgical procedures, and return of the fish to the wild. While these recommended practices were developed specifically for tropical tuna species, they are also likely applicable for other pelagic fishes. We present these guidelines to guide and promote the development of best practices for such procedures on pelagic species.
... Elasmobranchs (sharks, skates and rays) are among the most endangered vertebrate groups IUCN, 2022; because of the high occurrence of discarding events, additional to past and present targeting practices (Dulvy et al., 2014;IUCN, 2022;Molina & Cooke, 2012;Stevens et al., 2000;Zeller et al., 2018). Studies examining the consequences of fishing-capture focus mainly on physiological and immunological blood alterations, and immediate and delayed mortality (Frick, Reina, et al., 2010, Frick, Walker, et al., 2010, Frick et al, 2012Gallagher et al., 2014;Heard et al., 2014;Knotek et al., 2018;Mandelman et al., 2013;Van Rijn & Reina, 2010;Whitney et al., 2017). The few studies investigating the energetic cost of capture stress in elasmobranchs found opposite responses in different species. ...
In animals discarded after a fishing capture event, the elicited stress response necessary to ensure their survival is energetically costly. This energy is diverted from other important biological activities, including growth and reproduction, possibly impairing them. Given that elasmobranchs are among the most threatened vertebrate groups, estimating capture-induced energetic changes and comparing these variations to the energy requirements of pregnancy maintenance is necessary. In pregnant southern fiddler rays (Trygonorrhina dumerilii), we measured changes in oxygen uptake rate (ṀO2 ; a proxy for metabolic rate and energy usage) in response to trawling simulation and air exposure, and estimated the oxygen requirements of sustaining late-term pregnancy and embryos. ṀO2 was measured in pregnant females, before (prestress ṀO2 ) and after trawling simulation (after-capture ṀO2 ), and again after females gave birth (postpartum ṀO2 ). After-capture ṀO2 was 31.7% lower than ṀO2 measured in minimally stressed females, suggesting a reduction in energy expenditure. This reduction is likely triggered by an initially excessive energetic investment in the stress response, and is aimed at shutting down nonessential activities to redirect energy to processes fundamental for survival. Prestress ṀO2 was 78.5% higher than postpartum ṀO2 . Capture simulation decreased ṀO2 to values similar to those observed postpartum, suggesting a capture-induced reduction in oxygen and energy allocation to pregnancy and embryonic respiration, which could be associated with reproductive impairments. These data, by better estimating the impact of capture and discard on energetic requirements and reproductive fitness, may support the introduction of area and/or seasonal closures to fishing.
... Extreme physiological changes can lead to mortality, with sensitivity to capture and handling, and likelihood of severity varying between species (Dapp et al. 2016b). For example, Port Jackson (Heterodontus portusjacksoni) and wobbegong (Orectolobus spp.) sharks have high post-capture survival, while hammerheads (Sphyrna spp.) are more vulnerable to capture stress ( Gallagher et al. 2014;Dapp et al. 2016a). Likewise, postrelease survival varies among teleost species, from 98% for shallow-caught reef fishes (e.g. ...
... Estimates of PRM from 6 different gear types (longlines, tuna purse seines, drumlines, deep set buoys, gillnets, rod and reel) were made in 22 studies, monitoring 792 individuals from 16 species across commercial, recreational, and fishery-independent (i.e., research) fishing. Motivation for PRM studies included identifying safe and effective handling methods for tagging and/or release (Escalle et al., 2016a;Escalle et al., 2018;Gallagher et al., 2014;Schaefer et al., 2019), bycatch survivability (Benson et al., 2018;Campana et al., 2016), and gear associated risks (Sepulveda et al., 2015;Sulikowski et al., 2020). Longlining gear was most often monitored for instances of shark PRM (n = 9 studies), followed by tuna purse seines (n = 6 studies) often regarding FADs. ...
Satellite telemetry as a tool in marine ecological research continues to adapt and grow and has become increasingly popular in recent years to study shark species on a global scale. A review of satellite tag application to shark research was published in 2010, provided insight to the advancements in satellite shark tagging, as well as highlighting areas for improvement. In the years since, satellite technology has continued to advance, creating smaller, longer lasting, and more innovative tags, capable of expanding the field. Here we review satellite shark tagging studies to identify early successes and areas for rethinking moving forward. Triple the amount of shark satellite tagging studies have been conducted during the decade from 2010 to 2020 than ever before, tracking double the number of species previously tagged. Satellite telemetry has offered increased capacity to unravel ecological questions including predator and prey interactions, migration patterns, habitat use, in addition to monitoring species for global assessments. However, <17% of the total reviewed studies directly produced results with management or conservation outcomes. Telemetry studies with defined goals and objectives produced the most relevant findings for shark conservation, most often in tandem with secondary metrics such as fishing overlap or management regimes. To leverage the power of telemetry for the benefit of shark species, it remains imperative to continue improvements to tag function and maximize the outputs of tagging efforts including increasing data sharing capacity and standardization across the field, as well as spatial and species coverage. Ultimately, this review offers a status report of shark satellite tagging and the ways in which the field can continue to progress.
... The branch lines were composed of a 5-m-long monofilament nylon line 2.5 mm in diameter connected to a swivel, a wire leader 1 m in length, and a 17/0 circle hook. Drumlines consisted of a mooring with two attachment points: (1) a line running to the surface with a buoy and (2) a swivel connecting a 23-m monofilament ganglion line to a baited 16/0 circle hook (Gallagher et al. 2014). Both gears were checked every 90 min for shark presence. ...
Although many shark species display predictable and seasonal aggregations related to breeding activities, few studies have reported direct evidence of reproductive interactions of large sharks. In this context, the present study reports the first evidence of mating scars in female tiger sharks Galeocerdo cuvier at the Fernando de Noronha Archipelago (FEN), an oceanic remote insular system in the South Atlantic Ocean. Results from the records of seven wounded females suggest that mating activity may occur between February and August. These females measured between 267 and 372 cm in total length, which is aligned with previous studies reporting size at sexual maturity for Atlantic tiger sharks. Although some females exhibited healed wounds, three of them had fresh, open wounds. One of the females also had a swollen and red cloaca. We also report the first presumably gravid female tiger shark for the region. Although sporadic, the observations herein reported indicate the importance of FEN for tiger shark reproduction in western equatorial Atlantic waters. This finding is especially relevant as FEN has been identified as an important genetic hotspot for tiger sharks, with the largest global genetic diversity for the species.
... Previous studies on sharks reveal that they respond differently to physiological stress than other species. Thus, it can be hypothesized that their reaction may be species-specific (Beerkircher et al., 2002;Gallagher et al., 2014;Hyatt et al., 2012;Jerome et al., 2018;Mandelman and Skomal, 2009;Marshall et al., 2012;Morgan and Burgess, 2007) and likely influenced by many factors including the method of capture, duration of struggle, respiratory mode and metabolic scope . These responses are often measured through physiological changes in blood chemistry (e.g., changes in glucose, lactate, and acid-base status; (Skomal and Bernal, 2010) and electrolytes (Piiper et al., 1972) and have been used to determine the relative condition of the fish following a capture-event (Cliff and Thurman, 1984;Faggio et al., 2014;Fazio et al., 2013;Harrenstien et al., 2005;Wells et al., 1986). ...
The quantification of capture-related physiological stress is an important factor when assessing the potential for
post-release survival in sharks that are incidentally captured. In the absence of these biological data and when
the post-release fate is unknown, effective management plans cannot be formulated and may lead to highly
susceptible shark populations being overfished. Here, we measured the levels of lactate, glucose, alanine amino
transferase (ALT), aspartate amino transferase (AST), Ca2+, Na+ K+,Cl – Mg 2+ and Pi in the plasma of mature and
immature lesser spotted dogfish (Scyliorhinus canicula, herein dogfish) which were incidentally captured at two
depths (shallow: 50-200 m, and deep: 201-500 m) by bottom trawl off the coast of southern Sicily. These values
were used as biomarkers and physiological indicators of the secondary stress response associated with capture.
This study found that dogfish captured in deeper waters (below 200 m) had elevated levels of glucose, Na+,
Ca2+ and K+ compared to those inhabiting depths less than <200 m. We hypothesize that the elevated levels of
physiological stress in dogfish captured at greater depths may be related to the prolonged duration of the interactions
with the fishing gear in the area off southern Sicily. Our findings provide new data on the capturerelated
stress in dogfish and increase the understanding of the potential for post-release survival in sharks
captured at two depths by bottom trawl, information that is important for improving the general management
plans for the fishery. However, our PC Analysis results revealed that Maturity have a positive contribution from
the sample weight, sample length, ALT, AST and a negative contribution from Pi.
... Consequently, methods to mitigate mortality during C&R events have been investigated in many teleost species (see Muoneke et al., 2008;Brownscombe et al., 2017, for a reveiw). However, due to the difficulty of studying large, marine species in situ, there remains significant uncertainties surrounding best C&R practices and mortality rates due to species-specific responses to capture (Bartholomew and Bohnsack, 2005;Muoneke et al., 2008;Gallagher et al., 2014). For example, survival rates of large sport fish appear highly variable, with reported survivorship rates varying from 22% to 100% for common thresher sharks (Alopias vulpinus; Sepulveda et al., 2015), 90% for shortfin mako sharks (Isurus oxyrinchus; French et al., 2015), 100% for yellowfin tunas (Thunnus albacares) and bigeye tunas (Thunnus obesus; Holland et al., 1990) and 94-100% for ABFTs (Stokesbury et al., 2011;Marcek and Graves, 2014). ...
Catch-and-release (C&R) angling is often touted as a sustainable form of ecotourism, yet the fine-scale behaviour and physiological responses of released fish is often unknown, especially for hard-to-study large pelagic species like Atlantic bluefin tuna (ABFT; Thunnus thunnus). Multi-channel sensors were deployed and recovered from 10 ABFTs in a simulated recreational C&R event off the west coast of Ireland. Data were recorded from 6 to 25 hours, with one ABFT (tuna X) potentially suffering mortality minutes after release. Almost all ABFTs (n = 9, including tuna X) immediately and rapidly (vertical speeds of ~2.0 m s-1) made powered descents and used 50-60% of the available water column within 20 seconds, before commencing near-horizontal swimming ~60 seconds post-release. Dominant tailbeat frequency was ~50% higher in the initial hours post-release and appeared to stabilize at 0.8-1.0 Hz some 5-10 hours post-release. Results also suggest different short-term behavioural responses to noteworthy variations in capture and handling procedures (injury and reduced air exposure events). Our results highlight both the immediate and longer-term effects of C&R on ABFTs and that small variations in C&R protocols can influence physiological and behavioural responses of species like the commercially valuable and historically over-exploited ABFT.
... The removal of lactate is an important component of post-exercise recovery. Fighting the hook during capture depletes glycogen stores and generates lactate [8,9], possibly leading to acidosis [10,11]. In turn, postrelease recovery replenishes glycogen stores, removes lactate and restores homeostasis [10,12,13]. ...
Marine organisms normally swim at elevated speeds relative to cruising speeds only during strenuous activity, such as predation or escape. We measured swimming speeds of 29 ram ventilating sharks from 10 species and of three Atlantic bluefin tunas immediately after exhaustive exercise (fighting a capture by hook-and-line) and unexpectedly found all individuals exhibited a uniform mechanical response, with swimming speed initially two times higher than the cruising speeds reached approximately 6 h later. We hypothesized that elevated swimming behaviour is a means to increase energetic demand and drive the removal of lactate accumulated during capture via oxidation. To explore this hypothesis, we estimated the mechanical work that must have been spent by an animal to elevate its swim speed and then showed that the amount of lactate that could have been oxidized to fuel it comprises a significant portion of the amount of lactate normally observed in fishes after exhaustive exercise. An estimate for the full energetic cost of the catch-and-release event ensued.
... Overfishing is a major driver of decline for threatened sharks and rays across the globe . For S. mokarran, interactions with fishing gear are particularly concerning given their sensitivity to capture-related stress that results in high at-vessel and post-release mortality (Morgan & Burgess 2007;Gallagher et al., 2014;Gulak et al., 2015). This susceptibility was reflected by the post-release mortality of two sharks in this study, both caught on fishery independent longlines, despite being conducted in a way to minimize mortality. ...
The great hammerhead (Sphyrna mokarran) is a highly mobile, large‐bodied shark primarily found in coastal‐pelagic and semi‐oceanic waters across a circumtropical range. It is a target or bycatch species in multiple fisheries, and as a result, rapid population declines have occurred in many regions. These declines have contributed to the species being assessed as globally Critically Endangered on the IUCN Red List. While conservation and management measures have yielded promising results in some regions, such as the United States, high levels of at‐vessel and post‐release mortality remain a major concern to the species population recovery. We examined the vertical space use and thermal range of Pop‐Off Archival Satellite tagged S. mokarran in the western North Atlantic Ocean, expanding our understanding of the ecological niche of this species and providing insight into bycatch mitigation strategies for fisheries managers. Our results showed that S. mokarran predominantly used shallow depths (75% of records < 30 m) and have a narrow temperature range (89% of records between 23 and 28 °C). Individual differences in depth use were apparent and a strong diel cycle was observed, with sharks occupying significantly deeper depths during the daytime. Furthermore, two individuals were confirmed pregnant with one migrating from the Bahamas to South Carolina, USA providing further evidence of regional connectivity and parturition off the U.S. east coast. Our findings suggest that S. mokarran may be vulnerable to incidental capture in the western North Atlantic commercial longline fisheries due to substantial vertical overlap between the species and the gear. Our results can be incorporated into conservation and management efforts to develop and/or refine mitigation measures focused on reducing the bycatch and associated mortality of this species, which can ultimately aide S. mokarran population recovery in areas with poor conservation status.
... The smooth hammerhead shark is particularly vulnerable to hooking mortality in pelagic longline fisheries, with up to 71% of caught individuals being already dead upon gear retrieval (Coelho et al., 2012). Scalloped (S. lewini) and greater (S. mokarran) hammerhead sharks have also shown high sensitivity to capture and handling, substantially increasing their potential mortality upon release (Gallagher et al., 2014;Gulak et al., 2015). Although there are no direct studies on post-release mortality of smooth hammerhead shark, our results seem to indicate that this species is also vulnerable to increased potential mortality. ...
The increased risk of local extinction becomes critical for sharks depending on the narrow and isolated coastal habitats of oceanic islands. This includes large pelagic oceanic sharks that use such habitats as nurseries, as previously hypothesized for the smooth hammerhead Sphyrna zygaena, the least known of cosmopolitan large hammerhead sharks. We used a combination of acoustic and satellite telemetry in a juvenile population of Faial and Pico islands, Azores, mid-north Atlantic, to confirm if this isolated archipelago holds nurseries, and to answer questions related to their function and spatial–temporal stability. Our long-term acoustic tracking data showed a cluster of individual core home ranges in specific areas of north shore Faial, and surface positions from five Argos-linked tagged individuals also showed a clustering overlap in those areas for up to 1 year. These patterns seem to reveal a true habitat preference within the Faial-Pico island (sub) population of juvenile smooth hammerhead shark, and thus constitute strong evidence for this area to be considered a nursery. Some individuals remained in this nursery for up to 4 years, especially during summers. Sharks also showed a strong diel behavior, typically using the inshore nurseries during the day and moving further offshore during the night, during which they increased activity and dove deeper, most possibly to feed. We speculate that a combination of increased feeding opportunities, expanded trophic niche, and reduced predatory pressure may be a key evolutionary driver for the existence, prolonged use, and even preference of coastal nurseries at oceanic islands by juvenile smooth hammerhead shark. Given that these nurseries may constitute essential fish habitat for this species, they should be explicitly included in spatial management measures at the local and regional scales, as they may also play a role of greater importance to the north Atlantic population of this oceanic species.
... Sampling occurred from 2015 to 2018, across both wet (May-October) and dry (November-April) seasons. Sharks were targeted using a circle-hook drumline system (Gallagher et al. 2014a). Once caught, sharks were brought onto a platform or secured alongside the vessel, manually restrained, and provided with a ventilation pump system for the duration of data collection. ...
Serum proteins found in the blood have been used as diagnostic markers in both human and animal medicine. Evaluating proteins in the blood of sharks may be a valuable way to assess shark health. The purpose of this study was to perform serum protein electrophoresis from non-lethal blood samples of wild sharks and establish baseline values for six species off South Florida: blacknose (Carcharhinus acronotus), blacktip (Carcharhinus limbatus), bull (Carcharhinus leucas), lemon (Negaprion brevirostris), sandbar (Carcharhinus plumbeus), and tiger shark (Galeocerdo cuvier). Two hundred and fifty-one serum samples were collected between 2015-2018 along with sex determination and morphometric measurements. Agarose gel analysis was performed using mammalian protein fraction delimits albumin, alpha 1-globulins, alpha 2-globulins, beta globulins, and gamma globulins alternatively defined as fractions 1-5. Reference electrophoretic profiles were established for each species, revealing the dominance of protein fractions 3 and 4. The fraction 3:4 ratio was determined for each shark and reference intervals for total solids, protein fractions, and fraction 3:4 ratio are reported for each species. There were no significant differences in total solids or protein fractions between males and females of any species. In both blacktip sharks and bull sharks, total solids was positively correlated with body size, but not in the other species evaluated. In blacknose sharks, the fraction 3:4 ratio was positively correlated with body condition. Results suggest that there may be differences in total solids values across dry and wet seasons for some species. Newly established reference intervals can now be utilized in future research to evaluate the health of captive sharks and to investigate the health status of individuals in the wild as well as relate health measures to environmental conditions.
... Species' survival upon release needs consideration. Some studies indicate high levels of survival (Musyl & Gilman, 2018), whereas others indicate high mortality from capture stress (Gallagher et al., 2014). Some fishers in Sabah claim that sharks caught in gillnets are already dead, so discarding them would be wasteful . ...
In Southeast Asia elasmobranchs are particularly threatened. We synthesized knowledge from the peer‐reviewed and gray literature on elasmobranchs in the region, including their fisheries, status, trade, biology, and management. Our assessment included x species of sharkes and y species of rays. We found that 59% of assessed species are threatened with extinction and 72.5% are in decline; rays were more threatened than sharks. Research and conservation is complicated by the socioeconomic contexts of the countries, geopolitical issues in the South China Sea, and the overcapacity and multispecies nature of fisheries that incidentally capture elasmobranchs. The general paucity of data, funds, personnel, and enforcement hinders management. Reduced capacity in the general fishery sector and marine protected areas of sufficient size (for elasmobranchs and local enforcement capabilities) are among recommendations to strengthen conservation. Article impact statement: Sharks and rays in Southeast Asia are understudied and overfished, and their management is socioeconomically and geopolitically challenging. This article is protected by copyright. All rights reserved
... Prior experience may also influence the response to capture, as demonstrated for other forms of disturbance (Jordan et al., 2013). These possibilities are important because empirical studies show that fight time is a consistent correlate of physiological indicators of stress (Danylchuk et al., 2014;Gallagher et al., 2014;French et al., 2015;Whitney et al., 2017). Consequently, models of fight time can indicate the circumstances under which individuals may be more or less susceptible to capture-related impacts, even in the absence of physiological parameters. ...
Catch-and-release angling is widespread, but the impacts of this practice for captured individuals are understudied, especially among elasmobranchs. Studies on sub-lethal behavioural impacts are particularly sparse, despite their importance for the interpretation of biologging data and for assessments of species’ tolerance to capture. In this study, the behavioural responses of flapper skate (Dipturus intermedius) to catch-and-release angling were described for the first time, using archival observations (depth and temperature) for 21 tag deployment/retrieval events and five recreational angling events that occurred during tagged individuals’ time at liberty from charter vessels off the west coast of Scotland in 2016–17. During capture (8–50 minutes), the changes in depth and temperature experienced by individuals typically exceeded natural variability. Post-release, behavioural change was apparent from visual inspection, regression and functional data analysis of the time series. Immediately following release, movements into deeper water and short periods of low vertical activity (usually 1–2 hours in duration) were common. However, overall average vertical activity was typically around 38% higher in the 12 hours following release than in undisturbed activity. A small number of individuals (n = 3, 14%) exhibited irregular post-release behaviour in the form of rapid, transient re-ascents towards the surface following release. Collectively, the evidence for limited, short-term behavioural changes suggests that flapper skate behaviour is relatively resilient to catch-and-release angling from charter vessels, but irregular post-release behaviour in 14% of individuals is sufficiently notable to indicate that further research is required on the impacts of this practice. This study clearly demonstrates the value of biologging data and behavioural analyses for examining the impacts of disturbance and separating ‘disturbed’ and ‘undisturbed’ behaviours in studies of animal movement.
... From May 2008 to March 2020, we opportunistically targeted sharks using fisheries-independent longlines (described in Brooks et al. 2013;Talwar et al. 2020), drumlines (described in Gallagher et al. 2014), and conventional hook-and-line. Capture records reflect spatial and temporal variation in bait type, hook size, gear type, and fishing effort (i.e., a lack of captures at a given location does not imply an absence of sharks there, nor do more captures in an area imply higher abundance than elsewhere). ...
The Caribbean reef shark (Carcharhinus perezi) is an economically important species in The Bahamas, where it is protected from fishing and is a mainstay for the shark dive tourism industry. Significant declines in abundance are suspected throughout much of its range, making the study of its life history and spatial ecology important for effective fisheries management and conservation planning. We used tag-recapture data collected in The Bahamas between 2008 and 2020 to investigate the species’ linear movements, population characteristics, life history, and growth. Sharks moved little between tag and recapture events (range: 0 to 8 km) despite multiple years at liberty for many sharks (range: 2 days to 7.1 years). We found no evidence of seasonal migration. We used a combined-sex von Bertalanffy growth function to estimate an asymptotic mean length at age (TL∞) of 205.8 cm total length and a growth coefficient (k) of 0.06. Theoretical maximum longevity was 43.3 to 57.8 years. Median male length at maturity (L50) was 148.9 cm total length (95% CI: 146.1–151.5 cm), which likely occurs around 14.8 years of age. Our results indicate slower growth of the Caribbean reef shark in The Bahamas than previously estimated in Venezuela. Our results suggest the Caribbean reef shark may be more vulnerable to overfishing and extirpation at the northern extent of its range than previously considered and that large no-take areas may be an effective conservation tool for this species.
... The reasons for the poor recapture rate might include poor tag retention owing to the position where they were formerly tagged (i.e. on the posterior part of the pectoral fin in the case of roto tags[C-tags], which simply tore out) or because they were tagged incorrectly and not in the musculature at the base of the tail. Another reason for the low recapture rate could be post-release mortality from physiological stress or depredation(Laptikhovsky 2004;Heberer et al. 2010;Skomal and Mandelman 2012; Danylchuck et al. 2014;Gallagher et al. 2014;Mann et al. 2018;Mohan et al. 2020) ...
The diamond ray Gymnura natalensis is endemic to southern Africa where its preference for shallow coastal habitats makes it vulnerable to recreational shore-based angling. Although it makes up approximately 1% of the shore-based tag numbers, little is known about its movements, reproduction or population status in South Africa. This study used three independent long-term (34–41 years) datasets, including tagging by recreational anglers, competitive shore angling catches and shark net catches, to investigate the species’ movements, catch composition and population status in South Africa. Of the 3 739 individuals tagged (1984–2018), only 30 (1%) were recaptured after an average of 487 days at liberty. The majority (60%) of the recaptures occurred within 10 km of the release site, while 7% had moved more than 1 000 km along the coast. The longest recorded movements (1 577 and 1 756 km) were undertaken by adult rays tagged in the Western Cape Province moving to KwaZulu-Natal Province (KZN). The competitive shore angling catch (1977–2018; n = 9 150) from KZN was dominated by adult rays caught north of Durban, while the shark net catch in KZN (1981–2018; n = 584) was dominated by juvenile rays primarily from the central beaches of Durban. All the datasets exhibited strong seasonal trends with most catches taking place in summer. A risk assessment confirmed a stable to increasing population trend over four generations, suggesting that the population sampled along the east coast of South Africa should be classified as Least Concern.
... Oczywiście, niektóre z nich są wypuszczane, zwłaszcza gdy złowi się gatunek chroniony, a właściciel łódki nie chce problemów. Co z tego, skoro złapanie i wypuszczenie chociażby głowomłotów i tak będzie skutkowało ich śmiercią, ze względu na stres towarzyszący szarpaniu się na haczyku, który prowadzi do nagromadzenia kwasu mlekowego we krwi i prawdopodobnie do kwasicy mleczanowej (Gallagher, 2014). Można by stwierdzić, że ochrona kąpielisk siatkami mającymi powstrzymać rekiny przez wpływaniem na wody, w których spędzają czas ludzie jest bardzo dobrym i przemyślanym pomysłem. ...
... Oczywiście, niektóre z nich są wypuszczane, zwłaszcza gdy złowi się gatunek chroniony, a właściciel łódki nie chce problemów. Co z tego, skoro złapanie i wypuszczenie chociażby głowomłotów i tak będzie skutkowało ich śmiercią, ze względu na stres towarzyszący szarpaniu się na haczyku, który prowadzi do nagromadzenia kwasu mlekowego we krwi i prawdopodobnie do kwasicy mleczanowej (Gallagher, 2014). ...
... These measures can greatly enhance shark survival postrelease but may be ineffective if not enforced properly. Shore-based shark fishing (like all hook-and-line-based fisheries) can be physiologically stressful to sharks (Gallagher et al. 2014) and can leave them energy-depleted or injured once released, rendering them vulnerable to death or predation (Danylchuk et al. 2014;Weber et al. 2020). With an average of 11 sharks/angler and the number of permitted anglers able to fish in Florida, extrapolated catch rates are in the hundreds of thousands. ...
Shore‐based shark fishing in Florida is rarely monitored as it largely occurs at night on remote beaches and has received a questionable reputation after recent exposure of illegal activity. While these events have led to calls for better management and enforcement, the characteristics of the fishery itself remain largely unknown. Our study, therefore, provides the first comprehensive profile of the Florida shore‐based shark fishery to inform fisheries management and conservation. We distributed an online survey to all Florida Fish and Wildlife shore‐based shark fishing permit holders to gather data on angler sociodemographics, fishing preferences, habits, motivations, and perceptions of shark conservation. We identified three angler typologies that differed primarily by shark fishing experience and frequency: (1) experienced infrequent anglers, (2) skilled frequent anglers, and (3) novice infrequent anglers. Our results revealed that the Florida recreational shore‐based shark fishery itself has increased in participation fivefold since 2010 and generates approximately US$7.8 million (95% CI = $7.2– 8.5 million) annually in equipment expenditures and $34.3 million ($30.4–38.1 million) annually in fishing trips. Surveyed anglers caught a total of 9,617 sharks within a 12‐month period, averaging 11 sharks/angler, and the most preferred target species was the Blacktip Shark Carcharhinus limbatus. Angler motivations for participating in this fishery were grouped into the following categories: leisure and well‐being, experience of the catch, and consumption. Perceptions of shark conservation and management were generally positive; however, many anglers did not believe that recreational fishing negatively impacts shark populations. Most anglers expressed a desire to learn more about handling practices that benefited sharks, which may help managers implement more educational opportunities and communication efforts. Understanding the characteristics and perspectives of anglers from the shore‐based shark fishery in Florida is crucial for highlighting potential management pathways and estimating angler acceptance of management.
... Field sampling occurred with The University of Miami Shark Research and Conservation Program (SRC) during weekly sampling trips (as described in Tinari and Hammerschlag 2021). Sharks were captured using a circle-hook drumline system to minimize stress on the animal (described in Gallagher et al. 2014). To assess the microbiome, cell swabs were taken from the area between the lip and teeth (hereafter referred to as "mouth"), the inner side of the gill flaps (hereafter referred to as "gills"), the area of skin just below the dorsal fin laterally (hereafter referred to as "skin"), and lastly any area of visible injury (hereafter described as "wound"). ...
Bacteria are known to have explicit roles within the microbiomes of host tissues, therefore examining these communities may prove useful in assessing host health and responses to environmental change. The present study contributes to the emerging, yet understudied, field of microbiome research in elasmobranchs. We provide a screening of the culturable bacteria communities found on multiple tissue sites on the body surface of blacktip (Carcharhinus limbatus), bull (Carcharhinus leucas), and tiger (Galeocerdo cuvier) sharks near Miami, Florida. Tissue sites include mouth, gills, skin, and any visible wounds. The study adds to our understanding of the diversity of bacteria present on sharks in comparison to their natural environment. We also compare bacterial groups found within wounds in shark skin to healthy tissue sites on the same individual. Results indicate that wounds on an individual may allow for opportunistic bacteria to invade or overgrow where they would not normally be found, which may have potential health consequences for sharks that become wounded due to fishing practices. Identified bacteria belonged to the Actinobacteria, Firmicutes, and Proteobacteria phyla, known to be prominent bacterial groups associated with marine organisms. Results indicate shark species-specific differences in bacterial communities, including the presence of bacteria belonging to Planococcaceae exclusively on the skin of tiger sharks. To our knowledge, this is the first report of this family in any elasmobranch. While most tissue sites displayed commensal bacteria identified in similar studies, known pathogens belonging to Vibrionaceae and Staphylococcaceae were identified in the wounds of blacktip and bull sharks. Some bacteria may be normal residents, but the loss of protective dermal denticles due to a wound may allow colonization by pathogens. Continued research is needed to explore microbial communities associated with sharks and their influence on host health.
... There are many studies evaluating the vitality of captured fish as a golden method to infer their survival capacity, which are based on scoring the impairment of reflexes or the degree of external injuries [7]. However, it was described that fish released with no obvious signs of injury often show delayed mortalities days after being released [8,9]. In this sense, it was described that fishing processes elicited acute stress responses in captured fish [10,11], which caused physiological imbalances that could last for a longer time. ...
Evaluating the survival of discarded species is gaining momentum after the new European Common Fisheries Policy (Article 15 of the European Regulation No. 1380/2013). This regulation introduced a discard ban, with an exemption for those species with demonstrated high survival rates after their capture and release. Candidate species should be evaluated for each fishing gear and geographical area. In this study, we assessed not only survival, but also physiological recovery rates of blackspot seabream (Pagellus bogaraveo) below commercial size captured with a hookline called “voracera” in the Strait of Gibraltar (SW Atlantic waters of Europe). Experiments onboard a commercial fishing vessel were paralleled with studies in controlled ground-based facilities, where the capture process was mimicked, and physiological recovery markers were described. Our results confirmed that hookline capture induced acute stress responses in the target species, such as changes in plasma cortisol, lactate, glucose, and osmolality. However, 90.6% of the blackspot seabreams below commercial size captured with this fishing gear managed to survive, and evidenced physiological recovery responses 5 h after capture, with complete homeostatic recovery occurring within the first 24 h. Based on this study, the European Commission approved an exemption from the discard (EU Commission Delegated Regulation 6794/2018). Thus, the robust methodology described herein can be an important tool to mitigate the problem of discards in Europe.
... We tagged 96 tiger, great hammerhead and bull sharks (58, 18 and 20, respectively; Supporting information) throughout south Florida and The Bahamas between 2010 and 2017 ( Fig. 1 and Supporting information) using smart position and temperature transmitting satellite tags (SPOT; manufactured by Wildlife Computers) and following tagging procedures outlined in Gallagher et al. (2014) and Graham et al. (2016). Argos location accuracy ranges from < 250 m to > 5 km according to the pre-defined error classes: 3, 2, 1, 0, A, B and Z, where 'Z' reflects highly unreliable position estimates. ...
Animals follow specific movement patterns and search strategies to maximize encounters with essential resources (e.g. prey, favourable habitat) while minimizing exposures to suboptimal conditions (e.g. competitors, predators). While describing spatiotemporal patterns in animal movement from tracking data is common, understanding the associated search strategies employed continues to be a key challenge in ecology. Moreover, studies in marine ecology commonly focus on singular aspects of species' movements, however using multiple analytical approaches can further enable researchers to identify ecological phenomena and resolve fundamental ecological questions relating to movement. Here, we used a set of statistical physics-based methods to analyze satellite tracking data from three co-occurring apex predators (tiger, great hammerhead and bull sharks) that predominantly inhabit productive coastal regions of the northwest Atlantic Ocean and Gulf of Mexico. We analyzed data from 96 sharks and calculated a range of metrics, including each species' displacements, turning angles, dispersion, space-use and community-wide movement patterns to characterize each species' movements and identify potential search strategies. Our comprehensive approach revealed high interspecific variability in shark movement patterns and search strategies. Tiger sharks displayed near-random movements consistent with a Brownian strategy commonly associated with movements through resource-rich habitats. Great hammerheads showed a mixed-movement strategy including Brownian and resident-type movements, suggesting adaptation to widespread and localized high resource availability. Bull sharks followed a resident movement strategy with restricted movements indicating localized high resource availability. We hypothesize that the species-specific search strategies identified here may help foster the co-existence of these sympatric apex predators. Following this comprehensive approach provided novel insights into spatial ecology and assisted with identifying unique movement and search strategies. Similar future studies of animal movement will help characterize movement patterns and also enable the identification of search strategies to help elucidate the ecological drivers of movement and to understand species' responses to environmental change.
... These stranding events may be linked to reproductive activity or, as some individuals in this study had scars and wounds, could be attributable to fishing gear; it is possible that stress induced by fisheries interaction may result in shark stranding events (Williams et al., 2010). Fishes released alive after capture are often assumed to survive with minimal impacts; however, recent studies have shown that the direct effects of both targeted and incidental capture of sharks might result not only in premature parturition, but also in post-release mortality, even days after release (Gallagher et al., 2014;Adams et al., 2018). Retained fishing hooks, which are often underestimated, might also result in physical and physiological damage, with lethal consequences (Borucinska et al., 2002). ...
• The Mediterranean Sea represents an area of elevated risk of extinction for sharks, where data deficiency is a pervasive problem.
• To compensate for such a paucity of information, this study investigated the use of social media content as a complementary approach to evaluate the distribution and habitat use of the Critically Endangered blue shark Prionace glauca in coastal waters, as well as public perceptions of the sharks.
• Through social media data mining a total of 146 records, comprising 158 individual blue sharks approaching Italian coastal waters, have been recorded from 2011 to 2020.
• This study revealed that, over the past decade, blue sharks regularly visited Italian coastal habitats for extended periods of time. Differences in the temporal distribution of blue sharks by sex and size appear to be linked to reproductive activity. The higher number of adult females approaching the shore in spring and the increase in young-of-the-year (YOY) sightings in the following months possibly indicate parturition in coastal waters. Spatial analyses also showed that certain Italian coastal areas, such as those in Calabria and Puglia, were preferred coastal habitats for this species.
• Results also indicate that social media platforms can be considered an ever-growing source of data on wildlife, which can shed light on the occurrence and distribution of endangered shark species in poorly known habitats. Furthermore, social media platforms should be used for awareness campaigns to educate the public, as this study showed that negative reactions to shark encounters remain widespread.
... Sampling occurred opportunistically between 2015 and 2019 within Biscayne Bay, Florida, USA (25.61°N, 80.17°W) as part of an ongoing standarized shark survey (Tinari and Hammerschlag 2021). Sharks were captured using circlehook drumlines, a passive fishing technique that allows the captured sharks to swim (as described by Gallagher et al. 2014). Briefly, gear consisted of a submerged weight with two attachment points: (1) a line running to the surface with buoy floats and (2) a swivel connecting a 23-m monofilament ganglion line that terminated with a baited 16/05° -offset circle hook. ...
Energetic condition is one of the most important factors that influence fitness and reproductive performance in vertebrates. Yet, we lack evidence on how energetic states change in response to reproduction in large marine vertebrates. In the present study, we used a non-lethal approach to assess relationships among reproductive stage, circulating steroid hormones (testosterone and relative corticosteroid levels), plasma fatty acids, and the ketone body β-hydroxybutyrate in male sharks of two species with divergent ecologies, the benthic nurse shark (Ginglymostoma cirratum) and the epipelagic blacktip shark (Carcharhinus limbatus). We found higher relative corticosteroid levels in adult nurse sharks during the pre-mating period and in blacktip sharks during the mating period. Higher levels of β-hydroxybutyrate were found in adult nurse sharks during the mating period, but concentrations of this ketone body did not significantly vary across reproductive stages in blacktip sharks. We also detected reduced percentages of essential fatty acids during the mating period of both nurse and blacktip sharks. Taken together, our findings suggest that nurse and blacktip sharks differ in their energetic strategy to support reproduction, however, they likely rely on physiologically important fatty acids during mating, to support spermatogenesis.
... The data for this paper were collected as part of a multi-year, long-term research program evaluating the interannual behavior and physiology of large sharks throughout the coastal waters of The Commonwealth of The Bahamas (Gallagher et al., 2021). On July 23, 2020, a sub-adult tiger shark (Galeocerdo cuvier) was safely captured using a standardized circle-hook drumline (see Gallagher et al., 2017 (Gallagher et al., 2014). The individual shark was then secured alongside a 10 m center console research vessel while remaining submerged, where its sex and morphometric measurements were taken. ...
Animal-borne video camera systems have long-been used to capture the fine-scale behaviors and unknown aspects of the biology of marine animals. However, their utility to serve as robust scientific tools in the greater bio-logging research community has not been fully realized. Here we provide, for the first time, an application of 360-degree camera technology to a marine organism, using a large tiger shark as a proof-of-concept case study. Leveraging the three-dimensional nature of the imaging technology, we derived 224 seafloor habitat assessments over the course of the nearly 1-h track, whereby the shark was able to survey ∼23,000 square meters of seafloor; over three-times greater than the capacity of non 360-degree cameras. The resulting data provided detailed information on habitat use, diving behavior, and swimming speed, as well seafloor mapping. Our results suggest that 360-degree cameras provide complimentary benefits—and in some cases superior efficiency—than unidirectional video packages, with an enhanced capacity to map seafloor.
Understanding how elasmobranchs respond to stressors is imperative so that effective measures to reduce mortality be employed, whether in commercially captured animals or sharks and rays maintained in human care. Currently, reflex action mortality predictors (RAMPs) are the most reliable proxies to indicate an animal's condition state, commonly employed for both teleost and elasmobranchs. As our understanding of mortality predictors is evolving, is it necessary that traditional indicators be constantly reviewed and new proxies proposed, in order to improve the tools available for the best possible evaluation of a stressed individual. In this context, this review aimed to compile data on behavioral and visual proxies, along with the proposition of new proxies to guide professionals and assist them in identifying signs associated with alarming situations that might potentially result in the death of highly stressed individuals or sub-lethal effects at population level (migration, reproduction) that may seriously compromise the success of release measures.
Introduction
Shore-based shark fishing in Florida is a relatively low-cost and easy-access fishery which attracts a wide variety of experienced and inexperienced anglers leading to concerns about proper handling methods of captured fish that are released either voluntarily or to comply with regulations. Proper handling methods can help reduce post-release mortality among sharks, many of which are threatened with extinction. Therefore, we considered proper handling methods as a pro-environmental behavior, which has been linked with the use of different information channels to increase conservation knowledge.
Methods
We used data from an online questionnaire to understand where anglers of this fishery obtain information about fishing skills with a particular focus on fish handling techniques and best practices for catch-and-release. Then we included their main information channels in a series of hierarchical regression models with perceived conservation knowledge and support for fishery management to explain pro-environmental behavior regarding shark conservation.
Results
We found that most anglers learned about shore-based shark fishing through interpersonal communications with friends and family, but typically use the internet to learn more about fishing skills. While information channel use was not significantly associated with pro-environmental behavior, it was significantly associated with support for fisheries management, which in turn was associated with pro-environmental behavior among respondents.
Discussion
These findings can inform public educational outreach efforts to spread awareness of proper handling techniques and reduce instances of post-release mortality in sharks.
Recreational shark fisheries have been the subject of recent public attention because of the possible impacts on shark populations and conflicts between stakeholders. A case study is presented based on discussions that took place in summer 2018 about potential changes to policies regulating recreational land‐based shark fishing in Florida. Comments from public meetings and workshops (totalling 15.8 hours) and online comments (1,050) submitted to the Florida Fish and Wildlife Conservation Commission (FWC) were analysed using the lens of actor–network theory. The case study explores the intersection of conflicting stakeholder interests and types of knowledge, including how stakeholders variously defined the problem of user conflict in a coastal public space, and how they aligned themselves in relation to the problem and to each other. It further illustrates how shifting values and norms can intersect with changing technologies and environmental realities to produce new or increasing conflicts between natural resource user groups. This study underlines the importance and potential benefits of regulatory agencies explicitly and transparently engaging with value trade‐offs when managing conflicts among users of natural resources.
Despite being one of the most abundant, economically‐significant, reef‐associated shark species, little is known about the reproductive aspects of the Caribbean reef shark (Carcharhinus perezi). In the present study we report the first evidence of mating wounds and scars in female Caribbean reef sharks at the Fernando de Noronha Archipelago, a remote Marine Protected Area from the South Atlantic Ocean. Data from five females suggest this species mates mainly during the austral summer, between February and March. Given that the archipelago has been previously described as a nursery ground for the Caribbean reef shark, these results add information about the reproductive cycle of this species in the equatorial Atlantic Ocean. This article is protected by copyright. All rights reserved.
The pace of life hypothesis (POLS) predicts that personality traits, like activity and boldness, are positively correlated with growth and metabolism. Here, we assess whether personality could predict body mass, metabolic rate, and performance under stress for hatchery raised Atlantic salmon (Salmo salar) 15 months post fertilization. Personality was evaluated for individual fish using a series of repeated trials alongside two stressful events (PIT tagging, simulated transport), to determine performance under stress. Standard metabolic rate (SMR) was then assessed via intermittent flow respirometry, and the relationships between personality, body mass, performance, and SMR were evaluated. Fish displayed repeatable behaviours, but not in accordance with POLS hypothesis. Smaller fish were more active and responsive to stimuli, while personality was not associated with SMR. Although smaller fish and fish with higher SMR both performed better under stress, body mass was unrelated to SMR. We discuss the utility of supporting the occurrence of a wider range of growth rates and body sizes in hatchery environments, as a means of promoting greater stress tolerance as well as faster growth.
Shark dive ecotourism is a lucrative industry in many regions around the globe. In some cases, sharks are provisioned using bait, prompting increased research on how baited dives influence shark behavior and yielding mixed results. Effects on patterns of habitat use and movement seemly vary across species and locations. It is unknown, however, whether wide-ranging, marine apex predators respond to provisioning by changing their patterns of grouping or social behavior. We applied a tiered analytical approach (aggregation-gregariousness-social preferences) examining the impact of provisioning on the putative social behavior of tiger sharks (Galeocerdo cuvier) at a dive tourism location in The Bahamas. Using network inference on three years of acoustic tracking data from 48 sharks, we tested for non-random social structure between non-provisioned and provisioned monitoring sites resulting in 12 distinct networks. Generally considered a solitary nomadic predator, we found evidence of sociality in tiger sharks, which varied spatiotemporally. We documented periods of both random (n = 7 networks) and non-random aggregation (n = 5 networks). Three of five non-random aggregations were at locations unimpacted by provisioning regardless of season, one occurred at an active provisioning site during the dry season and one at the same receivers during the wet season when provision activity is less prevalent. Aggregations lasted longer and occurred more frequently at provisioning sites, where gregariousness was also more variable. While differences in gregariousness among individuals was generally predictive of non-random network structure, individual site preferences, size and sex were not. Within five social preference networks, constructed using generalized affiliation indices, network density was lower at provisioning sites, indicating lower connectivity at these locations. We found no evidence of size assortment on preferences. Our data suggest that sociality may occur naturally within the Tiger Beach area, perhaps due to the unusually high density of individuals there. This study demonstrates the existence of periodic social behavior, but also considerable variation in association between tiger sharks, which we argue may help to mitigate any long-term impacts of provisioning on this population. Finally, we illustrate the utility of combining telemetry and social network approaches for assessing the impact of human disturbance on wildlife behavior.
Lactate concentration ([lactate−]), pH, and bicarbonate concentration ([HCO3−]) were measured in the blood of salt-water crocodiles (Crocodylus porosus Schneider) exhausted during field capture. Body temperature after capture averaged 31·1 °C. All animals underwent high levels of anaerobic metabolism and metabolic acidosis. The largest animals attained the highest blood [lactate−] and lowest pH ever observed in any animal as a result of activity. Peak levels of [lactate−] increased with increasing body mass (slope = 9·72 mmol 1−1 logM−1; mass M in kg), indicating a greater anaerobic capacity in larger animals. Several large crocodiles had [lactate−] in excess of 50mmol 1−1. Blood pH decreased with mass (slope = 0·163 pH unitslogM−1) and reached 6·6 in the largest animals. One animal remained acidotic for several hours and had a minimal pH of 6·42. Blood increased significantly and [HCO3−] decreased significantly with increasing body mass. Struggling time before exhaustion was greater in larger animals, ranging from about 5min in small (<1 kg) crocodiles to over 30min in animals over 100 kg. During recovery, mean blood [lactate−] decrement after 2h was 6·0 mmol 1−1 and was not significantly related to mass. Proton elimination from the blood, however, was more rapid in larger animals (slope = 0·0443 μmol 1 −1 log M −1 ). The positive mass-dependence of acid-base disturbance could be related to the greater susceptibility of large crocodiles (>700 kg) to post-capture mortality.
Globally, ecosystems and their constituent flora and fauna face the localized and broad-scale influence of human activities.
Conservation practitioners and environmental managers struggle to identify and mitigate threats, reverse species declines,
restore degraded ecosystems, and manage natural resources sustainably. Scientific research and evidence are increasingly regarded
as the foundation for new regulations, conservation actions, and management interventions. Conservation biologists and managers
have traditionally focused on the characteristics (e.g. abundance, structure, trends) of populations, species, communities,
and ecosystems, and simple indicators of the responses to environmental perturbations and other human activities. However,
an understanding of the specific mechanisms underlying conservation problems is becoming increasingly important for decision-making,
in part because physiological tools and knowledge are especially useful for developing cause-and-effect relationships, and
for identifying the optimal range of habitats and stressor thresholds for different organisms. When physiological knowledge
is incorporated into ecological models, it can improve predictions of organism responses to environmental change and provide
tools to support management decisions. Without such knowledge, we may be left with simple associations. ‘Conservation physiology’
has been defined previously with a focus on vertebrates, but here we redefine the concept universally, for application to
the diversity of taxa from microbes to plants, to animals, and to natural resources. We also consider ‘physiology’ in the
broadest possible terms; i.e. how an organism functions, and any associated mechanisms, from development to bioenergetics,
to environmental interactions, through to fitness. Moreover, we consider conservation physiology to include a wide range of
applications beyond assisting imperiled populations, and include, for example, the eradication of invasive species, refinement
of resource management strategies to minimize impacts, and evaluation of restoration plans. This concept of conservation physiology
emphasizes the basis, importance, and ecological relevance of physiological diversity at a variety of scales. Real advances
in conservation and resource management require integration and inter-disciplinarity. Conservation physiology and its suite
of tools and concepts is a key part of the evidence base needed to address pressing environmental challenges.
From 1994–2005 the Commercial Shark Fishery Observer Program (CSFOP) placed fishery observ-ers aboard US bottom longline vessels engaged in directed fishing for sharks in the region from New Jersey to Louisiana, USA. Observers routinely recorded species specific at-vessel mortality as related to enduring the stress of longline capture. Data for 5 species of sharks (sandbar Carcharhinus plumbeus, blacktip Carcharhinus limbatus, dusky Carcharhinus obscurus, tiger Galeocerdo cuvier, scalloped hammerhead Sphyrna lewini, and great hammer-head Sphyrna mokarran) were analyzed in this study. Multiple stepwise linear regressions indicate that age group, soak time and bottom water temperature can be used as predictors of at-vessel mortality and that size restrictions, size selective gear, restricting the soak time and time/area closures may be beneficial to fisheries targeting large coastal sharks. RESUMEN El Programa de Observación de la Pesquería Comercial de Tiburones sitúo observadores durante el periodo 1994–2005 en naves pesqueras dedicadas específicamente a la pesca con palangre de especies costeras grandes de tiburones en la región comprendida entre los estados de New Jersey y Lousiana en la costa estadoun-idense. Estos observadores tomaron datos sobre la habilidad de diferentes especies para sobrevivir el estrés de la captura con palangre. En este estudio analizamos datos de seis especies (Carcharhinus plumbeus o tiburón trozo, Carcharhinus limbatus o tiburón macuira, Carcharhinus obscurus o tiburón arenero, Galeocerdo cuvieri o tintorera tigre, Sphyrna lewini o cornuda común, y Sphyrna mokarran o cornuda gigante). El múltiplo el retroceso lineal pro-gresivo indican que el uso de restricciones por tamaño, tiempo en el agua, tipo de equipo y el cierre de pesquerías por área o por periodo pueden beneficiar el manejo de las pesquerías de tiburones costeros grandes.
Data collected by fisheries observers aboard U.S. pelagic longline vessels were examined to quantify and describe elasmobranch bycatch off the southeastern U.S. coast (lat. 22°-35°N, long, 71°-82°W). From 1992 to 2000, 961 individual longline hauls were observed, during which 4,612 elasmobranchs (15% of the total catch) were documented. Of the 22 elasmobranch species observed, silky sharks, Carcharhinus falciformis, were numerically dominant (31.4% of the elasmobranch catch). The catch status of the animals (alive or dead) when the gear was retrieved varied widely depending on the species, with high mortalities seen for the commonly caught silky and night, C. signatus, sharks and low mortalities for rays (Dasyatidae and Mobulidae), blue, Prionace glauca; and tiger, Galeocerdo cuvier; sharks. Discard percentages also varied, ranging from low discards (27.6%) for shorfin mako, Isurus oxyrinchus, to high discards for blue (99.8%), tiger (98.5%), and rays (100%). Mean fork lengths indicated the majority of the observed bycatch - regardless of species - was immature, and significant quarterly variation in fork length was found for several species including silky; dusky, C. obscurus; night; scalloped hammerhead, Sphyrna lewini; oceanic whitetip, C. longimanus; and sandbar, C. plumbeus; sharks. While sex ratios overall were relatively even, blue, tiger, and scalloped hammerhead shark catches were heavily dominated by females. Bootstrap methods were used to generate yearly mean catch rates (catch per unit effort) and 95% confidence limits; catch rates were generally variable for most species, although regression analysis indicated significant trends for night, oceanic whitetip, and sandbar sharks. Analysis of variance indicated significant catch rate differences among quarters for silky, dusky, night, blue, oceanic whitetip, sandbar, and shortfin mako sharks.
Abstract—From 2001 to 2006, 71
pop-up satellite archival tags (PSATs)
were deployed on five species of
pelagic shark (blue shark [Prionace
glauca]; shortfin mako [Isurus oxyrinchus];
silky shark [Carcharhinus
falciformis]; oceanic whitetip shark
[C. longimanus]; and bigeye thresher
[Alopias superciliosus]) in the central
Pacific Ocean to determine speciesspecific
movement patterns and survival
rates after release from longline
fishing gear. Only a single postrelease
mortality could be unequivocally documented:
a male blue shark which
succumbed seven days after release.
Meta-analysis of published reports
and the current study (n=78 reporting
PSATs) indicated that the summary
effect of postrelease mortality for blue
sharks was 15% (95% CI, 8.5–25.1%)
and suggested that catch-and-release
in longline fisheries can be a viable
management tool to protect parental
biomass in shark populations.
Pelagic sharks displayed species-specific
depth and temperature ranges,
although with significant individual
temporal and spatial variability in
vertical movement patterns, which
were also punctuated by stochastic
events (e.g., El Niño-Southern Oscillation).
Pelagic species can be separated
into three broad groups based
on daytime temperature preferences
by using the unweighted pair-group
method with arithmetic averaging
clustering on a Kolmogorov-Smirnov
Dmax distance matrix: 1) epipelagic
species (silky and oceanic whitetip
sharks), which spent >95% of their
time at temperatures within 2°C of
sea surface temperature; 2) mesopelagic-
I species (blue sharks and
shortfin makos, which spent 95% of
their time at temperatures from 9.7°
to 26.9°C and from 9.4° to 25.0°C,
respectively; and 3) mesopelagic-II
species (bigeye threshers), which
spent 95% of their time at temperatures
from 6.7° to 21.2°C. Distinct
thermal niche partitioning based on
body size and latitude was also evident
within epipelagic species.
ABSTRACT: Pop-up satellite archival tags (PSATs) are
used to chronicle or ‘archive’ the habitat preferences,
horizontal and vertical movements, fishery interaction,
and post-release mortality rates of a variety of pelagic
animals. Though PSATs are valuable research tools,
lower-than-expected reporting rates, early detachment,
and incomplete data return remain problematic.
These issues were quantified by analysis of reporting
rates, retention times (i.e. the time period PSATs re -
mained attached), and the quantity of depth, temperature,
and geolocation data returned from 731 PSAT
deployments on 19 species in the authors’ database
and 1433 PSAT deployments on 24 species taken from
53 published articles. The reporting rate of PSATs de -
ployed by the authors (0.79, 95% CI = 0.76 to 0.82) was
not significantly different from the reporting rate calculated
from published studies (0.76, 95% CI = 0.74 to
0.78). PSAT reporting rates were lowest in species
undertaking large (~1000 m) vertical excursions (logistic
regression, p = 0.006), and reporting rates have
increased significantly over time (p = 0.02), presumably
because of better PSAT design and construction.
Tag retention increased with depth range of the tag -
ged species and pop-off latitude (Cox proportional
hazards models, p < 0.001), suggesting that pressure
(and/or temperature), biofouling, and wound infection
at the insertion site of the PSAT’s anchoring device
influenced this parameter. The quantity of data re -
turned by Argos satellites was affected by tag production
year, programmed pop-up period, depth range,
and manufacturer. Species-specific reporting rates
were used to make recommendations for future PSAT
sampling designs.
1. There has been considerable debate over the past decade with respect to wildlife provisioning, especially resultant behavioural changes that may impact the ecological function of an apex predator. The controversy is exemplified by the shark diving industry, where major criticisms based on inference, anecdote and opinion stem from concerns of potential behaviourally mediated ecosystem effects because of ecotourism provisioning (aka‘chumming’ or feeding).
2. There is a general lack of empirical evidence to refute or support associated claims. The few studies that have investigated the behavioural impacts of shark provisioning ecotourism have generated conflicting conclusions, where the confidence in such results may suffer from a narrow spatial and temporal focus given the highly mobile nature of these predators. There is need for studies that examine the potential behavioural consequences of provisioning over ecologically relevant spatial and temporal scales.
3. To advance this debate, we conducted the first satellite telemetry study and movement analysis to explicitly examine the long-range migrations and habitat utilization of tiger sharks (Galeocerdo cuvier) originating in the Bahamas and Florida, two areas that differ significantly with regards to the presence/absence of provisioning ecotourism.
4. Satellite telemetry data rejected the behaviourally mediated effects of provisioning ecotourism at large spatial and temporal scales. In contrast, to the restricted activity space and movement that were hypothesized, geolocation data evidenced previously unknown long-distance migrations and habitat use for both tiger shark populations closely associated with areas of high biological productivity in the Gulf Stream and subtropical western Atlantic Ocean. We speculate that these areas are likely critically important for G. cuvier feeding forays and parturition.
5. We concluded that, in the light of potential conservation and public awareness benefits of ecotourism provisioning, this practice should not be dismissed out of hand by managers. Given the pressing need for improved understanding of the functional ecology of apex predators relative to human disturbance, empirical studies of different species sensitivities to disturbance should be used to guide best-practice ecotourism policies that maximize conservation goals.
Sharks, turtles, billfish, and marine mammals are frequently caught accidentally in commercial fisheries. Although conservationists and fisheries managers encourage the release of these nontarget species, the long-term outcome of released animals is uncertain. Using blue sharks Prionace glauca, we developed a model to predict the long-term survival of released animals based on analysis of small blood samples. About 5% of the sharks were landed in obviously poor condition (lethargic and unresponsive to handling); these moribund sharks were sampled and euthanized. A subset of the remaining sharks was sampled and tagged with pop-up satellite archival tags (PSATs). Each of the PSATs that reported data (11 tags) showed that the sharks roamed at sea for at least 3 weeks postrelease. Five variables differentiated moribund sharks from survivors: Plasma Mg (moribund, 1.57 ± 0.08 mM; survivor, 0.98 ± 0.05 mM; P < 0.00001), plasma lactate (moribund, 27.7 ± 4.1 mM; survivor, 5.80 ± 2.96 mM; P < 0.001), erythrocyte heat shock protein 70 (Hsp70) mRNA (relative levels: Moribund, 3.96 ± 0.53; survivor, 1.00 ± 0.29; P < 0.005), plasma Ca (moribund, 3.70 ± 0.14 mM; survivor, 3.13 ± 0.11; P < 0.005), and plasma K (moribund, 7.01 ± 0.66 mM; survivor, 5.12 ± 0.44 mM; P < 0.05). These analyses were used to develop logistic regression models that could “predict” the long-term survival of captured sharks, including a larger group of sharks that we sampled but did not tag. The best logistic model, which incorporated Mg and lactate, successfully categorized 95% of fish of known outcome (19 of 20). These analyses suggest that sharks landed in an apparently healthy condition are likely to survive long term if released (95% survival based on biochemical analyses; 100% based on PSATs).
SUMMARY 1. Salt-water crocodiles, Crocodylus porosus Schneider, were catheter- ized and Po2, Pco2, pH and lactate concentration ((lactate)) were measured in arterial blood during rest and after forced exhaustive activity at 30°C. 2. Gas exchange ratio (R), calculated from blood Po2 and Pco2, decreased from about 1-0 to 0-3 during resting voluntary breath-holding and indicated CO2 sequestration in the body fluids. The mean value for R in undisturbed animals was 0-6, which substantiates the hypothesis that some CO2 excretion is extrapulmonary. 3. In vitro buffer value of true plasma was —23-5 +1-9 mmol HCO3~ 1~' pH" 1. In vivo buffer value, determined by short-term self titration with metabolic CO 2, was —12-2 + 4-7mmolHCO3~ I" 1 pH" 1. 4. Exhaustive activity for 5 min in laboratory animals resulted in pronounced metabolic lactacidosis: pH decreased approximately from 7-43 to 7-11 while lactate concentration increased from 1-2 to 20—30 mmoll" 1. The acidosis was reduced by respiratory compensation during the first hour of recovery and by metabolic adjustments that were practically complete after the third hour. Greater acidosis (pH down to 64) in larger field-captured animals was resolved over a longer period. 5. During recovery, lactate and proton fluxes between the blood and other tissue were uncoupled. 6. The virtual absence of the fixed-acid Bohr effect in C. porosus blood is adaptive in large individuals because it facilitates continued O2 uptake from the lung into blood which may be acidified by as much as 1 pH unit as a result of physical activity.
Between 1983 and 2004, nearly 12 000 shortfin mako (Isurus oxyrinchus), common thresher (Alopias vulpinus) and blue (Prionace glauca) sharks were tagged in the Southern California Bight; however, only 1.97% of these have been returned. One possible reason for this low return rate could be post-release mortality caused by capture stress from the experimental longline. Plasma catecholamine levels were analysed to evaluate stress levels in longline-captured, rod-and- reel-captured and unstressed docile sharks. The mean catecholamine values determined for the three tag-release species ranged from 6539 to 22 079 pg mL−1. The level of adrenaline found in moribund I. oxyrinchus (94 807 pg mL−1) was much higher than in either P. glauca (46 845 pg mL−1 )o rA. vulpinus (36 890 pg mL−1). In contrast, blood obtained from sharks that were landed within minutes had lower catecholamine values (P. glauca, 889 and 1347 pg mL−1; I. oxyrinchus, 2960 and 3946 pg mL−1, adrenaline and noradrenaline respectively). Among the nine I. oxyrinchus specimens that were recaptured long after their longline capture and release, the highest adrenaline level measured just before release was 33 352 pg mL−1. Because these mako sharks survived sufficiently long to be recaptured, their time-of-release catecholamine levels provide a conservative estimate of ∼80% viability on the longline-captured and released population.
Blue sharks Prionace glauca are the most frequently discarded fish species during com- mercial pelagic longline fishing operations worldwide, yet their post-release mortality rate has never been measured. A generalized linear model of 12 404 blue sharks observed during the Canadian Atlantic pelagic longline swordfishery suggested a hooking mortality of 12 to 13%, yet scientific examination of 902 of these sharks indicated that hooking mortality was actually higher. A random sample of 40 of these blue sharks were tagged with satellite pop-up archival transmission (PAT) tags, then monitored for periods of up to 6 mo after release. All of the surviving sharks exhibited a depth- holding recovery behaviour for a period of 2 to 7 d after release. All healthy sharks survived, while 33% of those that were badly injured or gut hooked subsequently died. Overall blue shark bycatch mortality in the pelagic longline fishery was estimated at 35%, while the estimated discard mortality for sharks that were released alive was 19%. Survival time models indicated that 95% of the mortal- ity occurred within 11 d of release, indicative of death by trauma rather than starvation. The annual blue shark catch in the North Atlantic was estimated at about 84 000 t, of which 57 000 t is discarded. A preliminary estimate of 20 000 t of annual dead discards for North Atlantic blue sharks is similar to that of the reported nominal catch, and could substantially change the perception of population health if incorporated into a population-level stock assessment.
Anthropogenic climate change is already apparent and will have significant, ongoing impacts on Australian fishes and their habitats. Even with immediate actions to reduce greenhouse gases, there will be sustained environmental changes. Therefore, it is necessary to consider appropriate adaptations to minimise detrimental impacts for both fishes and the human populations that utilise them. Climate change will have a range of direct effects on the physiology, fitness, and survivorship of Australia's marine, estuarine and freshwater fishes, but also indirect effects via habitat degradation and changes to ecosystems. Effects will differ across populations, species and ecosystems, with some impacts being complex and causing unexpected outcomes. The range of adaptation options and necessary levels of intervention to maintain populations and ecosystem function will largely depend on the vulnerability of species and habitats. Climate change will also have an impact on people who depend on fishes for food or livelihoods; adapting to a new climate regime will mean trade-offs between biological assets and socioeconomic drivers. Models can be used to help predict trends and set priorities; however, they must be based on the best available science and data, and include fisheries, environmental, socioeconomic and political layers to support management actions for adaptation.
Sharks are subjected to extensive commercial and recreational fisheries worldwide. Current management, which imposes bag limits, minimum sizes, and quotas, mandates the release of large numbers of sharks each year, but little is known of post-release behavior and survivorship. Using animal-borne imaging technology, we examined the effects of handline capture on post-release behavior of six grey reef sharks, Carcharhinus amblyrhynchos, at Johnston Atoll (Central Pacific) as it relates to physical trauma and physiological stress induced by capture. To quantify the extent of physical trauma, 25 grey reef sharks (including these six), ranging from 56-135 cm fork length, were examined for evidence of external tissue damage after 2.0-12.8 minutes of handline capture. In addition, these fish were blood sampled to quantify relative changes in acid-base biochemistry. Although blood lactate increased and blood bicarbonate decreased significantly relative to the duration of the capture event, blood pH did not drop significantly and there was no evidence of respiratory or metabolic acidoses. Post-release behavior, as evidenced by animal-borne imaging, included group (n=3) and solitary (n=2) activities that had been previously described in this species. A single shark exhibited aberrant behavior, which included a two-minute period of disorientation, lack of movement, and loss of equilibrium; this behavior was attributed to extensive physical trauma associated with hook damage. When coupled with quantified information relative to the capture event, we found that animal-borne imaging is a useful tool for collecting direct observations of post-release behavior in sharks so that fishery managers and researchers can better assess the impacts of various capture techniques.
Exploitation of fishery resources has become a major conservation issue on a global scale. Commercial fisheries have been
repeatedly blamed for the worldwide declines in fish populations. However, we contend that the recreational fishing sector
also has the potential to negatively affect fish and fisheries. Here we present evidence to show that both recreational and
commercial fishing sectors deserve consideration as contributors to the exploitation of fish in marine and inland waters.
The lack of global monitoring and compiling of statistics on recreational fishing participation, harvest, and catch-and-release
has retarded our ability to understand the magnitude of this fishing sector. Using data from Canada, we estimate that the
potential contribution of recreational fish harvest around the world may represent approximately 12 percent of the global
fish harvest. Failure to recognize the potential contribution of recreational fishing to fishery declines, environmental degradation,
and ecosystem alterations places ecologically and economically important resources at risk. Elevating recreational fishing
to a global conservation concern would facilitate the development of strategies to increase the sustainability of this activity.
Predators can impact ecosystems through trophic cascades such that differential patterns in habitat use can lead to spatiotemporal variation in top down forcing on community dynamics. Thus, improved understanding of predator movements is important for evaluating the potential ecosystem effects of their declines.
We satellite-tagged an apex predator (bull sharks, Carcharhinus leucas) and a sympatric mesopredator (Atlantic tarpon, Megalops atlanticus) in southern Florida waters to describe their habitat use, abundance and movement patterns. We asked four questions: (1) How do the seasonal abundance patterns of bull sharks and tarpon compare? (2) How do the movement patterns of bull sharks and tarpon compare, and what proportion of time do their respective primary ranges overlap? (3) Do tarpon movement patterns (e.g., straight versus convoluted paths) and/or their rates of movement (ROM) differ in areas of low versus high bull shark abundance? and (4) Can any general conclusions be reached concerning whether tarpon may mitigate risk of predation by sharks when they are in areas of high bull shark abundance?
Despite similarities in diet, bull sharks and tarpon showed little overlap in habitat use. Bull shark abundance was high year-round, but peaked in winter; while tarpon abundance and fishery catches were highest in late spring. However, presence of the largest sharks (>230 cm) coincided with peak tarpon abundance. When moving over deep open waters (areas of high shark abundance and high food availability) tarpon maintained relatively high ROM in directed lines until reaching shallow structurally-complex areas. At such locations, tarpon exhibited slow tortuous movements over relatively long time periods indicative of foraging. Tarpon periodically concentrated up rivers, where tracked bull sharks were absent. We propose that tarpon trade-off energetic costs of both food assimilation and osmoregulation to reduce predation risk by bull sharks.
Catch-and-release recreational angling has become very popular as a conservation strategy and as a fisheries management tool for a diverse array of fishes. Implicit in catch-and-release angling strategies is the assumption that fish experience low mortality and minimal sub-lethal effects. Despite the importance of this premise, research on this topic has focused on several popular North American sportfish, with negligible efforts directed towards understanding catch-and-release angling effects on alternative fish species. Here, we summarise the existing literature to develop five general trends that could be adopted for species for which no data are currently available: (1) minimise angling duration, (2) minimise air exposure, (3) avoid angling during extremes in water temperature, (4) use barbless hooks and artificial lures/flies, and (5) refrain from angling fish during the reproductive period. These generalities provide some level of protection to all species, but do have limitations. Therefore, we argue that a goal of conservation science and fisheries management should be the creation of species-specific guidelines for catch-and-release. These guidelines would take into account the inter-specific diversity of fishes and variation in fishing techniques. As recreational angling continues to grow in popularity, expanding to many developing countries, and targeting alternative species, it is important that reasonable data appropriate for specific fish and fisheries are available. The sustainable use and conservation of recreational fishery resources will depend upon the development and dissemination of effective catch-and-release angling strategies based upon sound science to stakeholders around the world.