Carcharhinus Leucas Research Articles

A new metric for measuring condition in large predatory sharks.

A simple metric (span condition analysis; SCA) is presented for quantifying the condition of sharks based on four measurements of body girth relative to body length. Data on 104 live sharks from four species that vary in body form, behaviour and habitat use (Carcharhinus leucas, Carcharhinus limbatus, Ginglymostoma cirratum and Galeocerdo cuvier) are given. Condition shows similar levels of variability among individuals within each species. Carcharhinus leucas showed a positive relationship between condition and body size, whereas the other three species showed no relationship. There was little evidence for strong differences in condition between males and females, although more male sharks are needed for some species (e.g. G. cuvier) to verify this finding. SCA is potentially viable for other large marine or terrestrial animals that are captured live and then released.

Captura de tiburones en la region noroccidental de Cuba

Sharks have been important as seafood source and fisheries revenue in Cuba. Nevertheless, current information about this group of fishes in Cuba is scarce and in the last decades they have not been the focus of any organized research. From October 2009 to June 2011, fisheries and biological (229 sharks examined) data were collected at four landing sites in the northwest of Cuba. At present, there is no organized fishery specifically targeting only sharks along the northwest coast of Cuba, but they are caught as a component of multispecies fisheries on the insular shelf and as bycatch in longline fisheries targeting billfishes. We registered a total of 17 species, six in the commercial fishery, dominated by Carcharhinus perezii, Sphyrna mokarran, and Carcharhinus leucas, and 14 in the sport fishery (i.e., small-scale artisanal, not recreational properly), dominated by Isurus oxyrinchus, Isurus paucus, Carcharhinus longimanus, Carcharhinus falciformis, Galeocerdo cuvier and Prionace glauca. Mean CPUE by months in sport fishing varied from 0.43 to 4.44 number of sharks caught per ten fishing trips. Most oceanic sharks caught in the Cuban sport fisheries are highly migratory species and their populations show great ecological connectivity throughout the Gulf of Mexico and adjacent waters. This fact and the presence of a high proportion of individuals of C. longimanus and C. falciformis below maturity size are important results to be considered for regional conservation of sharks and planning rational use of shark fisheries.

Mercury accumulation in sharks from the coastal waters of southwest Florida.

As large long-lived predators, sharks are particularly vulnerable to exposure to methylmercury biomagnified through the marine food web. Accordingly, nonlethal means were used to collect tissues for determining mercury (Hg) concentrations and stable isotopes of carbon (δ(13)C) and nitrogen (δ(15)N) from a total of 69 sharks, comprising 7 species, caught off Southwest Florida from May 2010 through June 2013. Species included blacknose (Carcharhinus acronotus), blacktip (C. limbatus), bull (C. leucas), great hammerhead (Sphyrna mokarran), lemon (Negaprion brevirostris), sharpnose (Rhizoprionodon terraenovae), and tiger sharks (Galeocerdo cuvier). The sharks contained Hg concentrations in their muscle tissues ranging from 0.19mg/kg (wet-weight basis) in a tiger shark to 4.52mg/kg in a blacktip shark. Individual differences in total length and δ(13)C explained much of the intraspecific variation in Hg concentrations in blacknose, blacktip, and sharpnose sharks, but similar patterns were not evident for Hg and δ(15)N. Interspecific differences in Hg concentration were evident with greater concentrations in slower-growing, mature blacktip sharks and lower concentrations in faster-growing, young tiger sharks than other species. These results are consistent with previous studies reporting age-dependent growth rate can be an important determinant of intraspecific and interspecific patterns in Hg accumulation. The Hg concentrations observed in these sharks, in particular the blacktip shark, also suggested that Hg may pose a threat to shark health and fitness.

Distribution and dynamic habitat use of young bull sharks Carcharhinus leucas in a highly stratified northern Gulf of Mexico estuary.

Understanding how animals alter habitat use in response to changing abiotic conditions is important for effective conservation management. For bull sharks (Carcharhinus leucas), habitat use has been widely examined in the eastern and western Gulf of Mexico; however, knowledge of their movements and the factors influencing them is lacking for populations in the more temperate north-central Gulf of Mexico. To examine how changes in hydrographic conditions affected the presence of young bull sharks in Mobile Bay, Alabama, thirty-five sharks were fitted with internal acoustic transmitters and monitored with an acoustic monitoring array consisting of thirty-three receivers between June 2009 and December 2010. Tagged sharks ranged in size from 60 to 114 cm fork length and were detected between the upper and lower portions of Mobile Bay. Despite a variety of freshwater sources associated with this highly productive estuary, sharks were most consistently detected at the largest input to the system – the Mobile and Tensaw Rivers. Our findings suggest a combination of hydrographic factors interact to influence the distribution of juvenile bull sharks in Mobile Bay. The factors affecting the probability of detecting at least one bull shark varied both temporally (2009 vs 2010) and spatially (upper vs lower bay). Electivity analysis demonstrated that bull sharks showed highest affinity for warm water (29–32°C), moderate salinities (10–11 psu) and normoxic waters (5–7 mg/l), although these patterns were not consistent between regions or across years. We suggest future studies coupling telemetry and hydrographic variables should, when possible, consider the interactions of multiple environmental parameters when defining the dynamic factors explaining the spatial distribution of coastal sharks.

The complete mitochondrial DNA of the bull shark (Carcharhinus leucas)

The bull shark mitochondrial structure is similar to that of other elasmobranchs; it has a total length of 16,100 bp, the base composition of the genomes was as follows: A (31.35%), T (31.35%), C (24.38%) and G (12.90%). It contains 13 protein-coding genes and 23 tRNA genes. The tRNA genes range from 70–72 bp. Gene order is the same as in other vertebrates and teleosts.

Age and Growth of the Bull Shark in the Western North Atlantic Ocean

AbstractAge and growth estimates for the Bull Shark Carcharhinus leucas were derived from 121 vertebral centra collected from Bull Sharks (59.1–223.5cm FL) between 1966 and 2010 in the western North Atlantic Ocean. Size at birth was confirmed with an additional 20 embryos (44.2–54.4cm FL). The maximum age based on vertebral band pair counts was 25 (184cm FL) and 27 (196cm FL) years for males and females, respectively. The logistic and Gompertz growth models fitted the size‐at‐age data best for males and females, respectively. Based on previously published estimates of length at maturity, males mature at 15–17years (176–185cm FL) and females at 15years (189cm FL). Bull Sharks in the western North Atlantic Ocean and the Gulf of Mexico have similar growth rates and reach similar sizes at age.

Toward a Sustainable Fishery Management Policy

This article proposes an Artificial Neural Network (ANN) model to predict neonatal and juvenile bull shark habitat usage in the Sabine Pass, located within the Gulf of Mexico between Louisiana and Texas. Given continuing discussion regarding overfishing of all shark species, including bull sharks, in the northwestern Atlantic and Gulf of Mexico, the research objective was to analyze environmental data proven to be conducive to bull shark early life stages and to use these data in an ANN to predict bull shark presence during late spring and throughout summer months at designated sampling sites. The results of this analysis can both aid decision making in a fisheries context and inform the discussion on bull shark habitat usage in general, thereby contributing to the discussion of whether or not the need exists for conservation efforts to ensure sustainability of the species as part of an effective bull shark management plan.

Common Sharks of Florida

Florida’s shark population is diverse and includes species that range in size from only a few feet to more than 40 feet in total length. Experts caution sea-goers to beware of sharks 6 feet or longer due to the damage they can cause in a single bite. Among the species that grow to this size and have been known to attack humans are bull sharks, tiger sharks, and great white sharks. Whites are seasonal visitors to Florida waters, and bulls and tigers are year-round residents, along with these other common species. This revised 4-page fact sheet was written by Florida Sea Grant, and published by the UF Department of Sea Grant, September 2013.

Physiological stress response, reflex impairment, and survival of five sympatric shark species following experimental capture and release

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 sus- tainable, 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-spe- cific 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: hammer- head 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 phenom- ena. 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.

Long-Term Changes in Species Composition and Relative Abundances of Sharks at a Provisioning Site

Diving with sharks, often in combination with food baiting/provisioning, has become an important product of today’s recreational dive industry. Whereas the effects baiting/provisioning has on the behaviour and abundance of individual shark species are starting to become known, there is an almost complete lack of equivalent data from multi-species shark diving sites. In this study, changes in species composition and relative abundances were determined at the Shark Reef Marine Reserve, a multi-species shark feeding site in Fiji. Using direct observation sampling methods, eight species of sharks (bull shark Carcharhinus leucas, grey reef shark Carcharhinus amblyrhynchos, whitetip reef shark Triaenodon obesus, blacktip reef shark Carcharhinus melanopterus, tawny nurse shark Nebrius ferrugineus, silvertip shark Carcharhinus albimarginatus, sicklefin lemon shark Negaprion acutidens, and tiger shark Galeocerdo cuvier) displayed inter-annual site fidelity between 2003 and 2012. Encounter rates and/or relative abundances of some species changed over time, overall resulting in more individuals (mostly C. leucas) of fewer species being encountered on average on shark feeding dives at the end of the study period. Differences in shark community composition between the years 2004–2006 and 2007–2012 were evident, mostly because N. ferrugineus, C. albimarginatus and N. acutidens were much more abundant in 2004–2006 and very rare in the period of 2007–2012. Two explanations are offered for the observed changes in relative abundances over time, namely inter-specific interactions and operator-specific feeding protocols. Both, possibly in combination, are suggested to be important determinants of species composition and encounter rates, and relative abundances at this shark provisioning site in Fiji. This study, which includes the most species from a spatially confined shark provisioning site to date, suggests that long-term provisioning may result in competitive exclusion among shark species.

Mitochondrial genome of the bull shark Carcharhinus leucas (Carcharhiniformes: Carcharhinidae)

The bull shark Carcharhinus leucas is a large elasmobranch species widespread in tropical and warm oceans, rivers and lakes. We first determine the complete mitogenome of C. leucas in this article. It is 16,704 bp in length, consists 37 genes and one control region with the typical gene order in vertebrates. The ND6 gene used the rare AGG as stop codon. The 22 tRNA genes ranged from 67 to 75 bp. The tRNA-Ser2 lacks the dihydrouridine arm and cannot form the typical cloverleaf structure. The control region is 1066 bp in length with high A + T and low G contents.

The use of permanent magnets to reduce elasmobranch encounter with a simulated beach net. 1. The bull shark (Carcharhinus leucas)

Beach nets are protective nets used to minimize interactions between potentially dangerous sharks and beachgoers. Studies have demonstrated that beach nets are substantial contributors to elasmobranch mortality. One hypothesized solution to reducing this mortality is the use of permanent magnets. The present study examined the effects of grade C8 barium-ferrite (BaFe12O19) permanent magnets on bull shark (Carcharhinus leucas) behavior, a species frequently entangled in beach nets. To examine this effect, two experiments were conducted: bait and barrier experiments. Log-linear models, more specifically, Poisson regressions were used to test hypotheses pertaining to the effects of treatment type, conspecific density, water visibility, and year on shark behavior. For the bait experiment, the magnetic treatment significantly reduced feeding frequency and increased avoidance frequency, with Poisson regressions also demonstrating that conspecific density was a significant predicator of avoidance and feeding frequencies. For the barrier experiment, the magnetic treatment reduced entrance frequency and yielded an increased avoidance frequency, with Poisson regressions also demonstrating that water visibility was inversely correlated to entrance frequency. This study is the first to demonstrate that C. leucas can be deterred by permanent magnets and that magnet efficacy can vary based on situational context. While this study sheds light on the potential for permanent magnets as devices that may reduce C. leucas encounters with protective beach nets, research on magnet exclusion properties should be conducted prior to applying this concept to future shark exclusion technologies.

Know Your Instruments: Ensuring Depth and Temperature Data from Pop- Up Satellite Archival Tags Are Reported Correctly

Pop-up satellite archival tags (PSATs) are electronic devices attached externally to aquatic animals that collect data such as light-level, pressure and temperature. After the PSAT has popped off and floats to the sea surface, archived data are transmitted via the Argos satellite system to the user, eventually providing insight into the spatial ecology of the study animals. Raw data received via the Argos satellite system are either processed directly by the manufacturer of the tag, or the tag manufacturer provides the user with custom-made analysis software, both resulting in data conditioned in files that can then be used for further analysis. Here I argue that insufficient knowledge by users about how PSATs record, archive and transmit data can be problematic. I revisit a dataset previously published from adult bull sharks Carcharhinus leucas to give an example of how erroneous depth and temperature data can slip into the peer-reviewed literature. I encourage PSAT users to engage in personal communication with tag manufacturers in order to understand how PSATs record, archive, process and transmit data. I argue that scientists must accurately report what data from PSATs they included and/or excluded in the analysis in order to avoid the publication of incomplete data.

What appears to be a defensive behavior in the anchovy could also be a double-edged sword

TheanadromousanchovyspeciesStolephoruscommersonniiis a schooling fish found in Indo-Pacific areas, with a pref-erence for brackish waters. It features in the diet of manypredators, including juvenile reef-associated sharks (Heupeland Hueter 2002). However, this small species (max. length:10 cm) is not supposed to be foraged by the bull sharkCarcharhinus leucas, whose adult specimens do not feed onsuch small prey (Werry et al. 2012). Here, we report uponadult bull sharks preying,at sunset, on an anchovy school onMarch 29, 2012, near the pass ‘‘Mtsamboro’’ north ofMayotte(southwesternIndianOcean).Thisunusualforagingpattern may be triggered by the defensive behavior in theanchovy toward black skipjack Euthynnus affinis.In response to skipjack predation, the anchovy gatheredintoacompactschoolformation(Fig. 1a).Withinthisschool,individualanchovieswerevirtuallyindistinguishableandtheskipjack seemed incapable of targeting an individual fish.However, when this compact school took on the appearanceof a single prey, it triggered the attack of the bull sharks(Fig. 1b), which were uninterested in isolated anchovies.Successive attacks by predators continued until the an-chovy school disappeared; the shark attacks initially brokeup the cohesion of the school, permitting the skipjack tohunt isolated anchovies, which immediately reorganizedthemselves into one or more smaller schools. Thisregrouping had the effect of triggering further shark attacks.This report shows that in ecosystems with complexbiomass structure such as a coral reef, the hunting patternsof different species may be mutually beneficial. It is com-mon to refer to the interactions among species of high tro-phic-chain levels as intraguild predation (Arim and Marquet2004); however the win–win outcome interaction betweenpredators reported here is, as yet, rarely discussed.Acknowledgments We are grateful to Yannick Stephanfrom ‘‘Mayotte De´couverte’’, for providing the photo-graphs.

First reports of proliferative lesions in the great white shark, Carcharodon carcharias L., and bronze whaler shark, Carcharhinus brachyurus Günther

The low incidence of reported tumours in elasmobranchs has led to the assumption that the group rarely develops cancerous diseases (Loprinzi et al. 2005). This, combined with some studies reporting a therapeutic benefit in cartilage extract (e.g. Cho & Kim 2002), has resulted in a worldwide demand for shark cartilage products for use as alternative therapies (Berzins & Hovland 1999). This demand has, at least in part, increased the pressure on shark populations contributing to their worldwide decline (Ostrander et al. 2004). While reported cases are relatively low, both benign and cancerous proliferative lesions have been reported in 21 species of sharks from over 9 families (Ostrander et al. 2004; National Cancer Institute 2007). Cutaneous neoplasms have been reported in a number of elasmobranchs including the tiger shark, Galeocerdo cuvier (M€ uller and Henle) (Ostrander et al. 2004), the smooth dogfish, Mustelus canis Mitchill (Wolke & Murchelano 1976), and the bull shark, Carcharhinus leucas M€ uller and Henle (Harshbarger 1972). Odontogenic, oral and gingival neoplasms are well documented in bony fish (Harshbarger & Clark 1990; Grizzle & Goodwin 1998) and were reported from sharks including the grey nurse shark, Carcharias taurus Rafinesque, and blue shark, Prionace glauca L. (Borucinska et al. 2004). Various studies and observations suggest a relationship between tumour development and environmental contamination in other species (McAloose & Newton 2009). Rates of reported neoplasm in marine mammals have steadily increased over the past two decades including newly described and resurging diseases, giving rise to concern whether such tumours could be reflective of environmental distress syndrome triggered by human-related activities (Bossart 2007). This study describes the first observations of proliferative, possibly neoplastic, lesions in two elasmobranch species: a great white shark, Carcharodon carcharias L., and a bronze whaler, Carcharhinus brachyurus G€ unther observed at the Neptune Islands in South Australia. Photographic images of white sharks at the Neptune Islands, South Australia, were obtained by still cameras or through the use of a camera mounted on a handheld pole, as part of an ongoing photographic identification database program. Each photograph was categorized based on the sex of the shark; approximate size; pigment patterns from the gill, dorsal, ventral fin and caudal fin regions; and permanent markings such as major scars; notches on the dorsal fin; and amputations or mutilations. In addition to its use for identification, the database is also used to document incidences of white shark injuries and to record resighting rates of sharks from year to year. Correspondence R Robbins, Fox Shark Research Foundation, 73 Ninth Avenue, Joslin, SA 5070, Australia (e-mail: rachel@sharkfoundation.com)

Evidence of shark attacks on Atlantic spotted dolphins (Stenella frontalis) off Bimini, The Bahamas

The rate of shark predation on small cetaceans is poorly understood, but information is increasing as more long-term cetacean and shark studies are conducted. Resident Atlantic spotted dolphins (Stenella frontalis), off the coast of Bimini, The Bahamas, have been the subject of ongoing photo-ID and behavioral studies since 2001. Sharks in this area have also been systematically documented for decades. Despite these efforts, an actual shark attack on a dolphin has not been observed in Bimini and such an observation is rare anywhere in the world. Because of this, photo-ID records were analyzed for evidence of shark-induced injuries, often in the form of a crescent-shaped injury or scar. Fifteen percent of cataloged individuals within the Bimini dolphin population exhibit evidence of a shark attack. Patterns in the location on the body of the attack and trends related to age and sex were calculated. There were few injuries to the ventral portion of the body, where most attacks would likely be fatal. Although the level of healing prevented most scars from being linked to a specific shark species, we suspect bull (Carcharhinus leucas), tiger (Galeocerdo cuvieri), shortfin mako (Isurus oxyrinchus) and dusky sharks (Carcharhinus obscures) to be possible predators of dolphins near Bimini. This study does not estimate the frequency of attacks on dolphins; here, we estimate the occurrence of unsuccessful attacks. Introduction: The amount of information on shark predation on small cetaceans is increasing as longitudinal cetacean projects and anecdotal information are compiled. Stomach content studies have shown delphinid species consumed by the following shark species: Zambesi/bull (Carcharhinus leucas), tiger (Galeocerdo cuvieri), great white (Carcharodon carcharias), and dusky (Carcharhinus obscures)(Cockcroft et al., 1989). First hand observations are rare (Mann & Barnett, 1999; Maldini, 2003) so alternative methods for assessing shark predation must be developed. One method is by assessing failed attempts; that is, documenting fresh injuries and scars on known dolphins that can be attributed to sharks, as was done in this study. Here, the percentage of Atlantic spotted dolphins, from a known population, with evidence of past shark attacks was determined and compared to other dolphin populations. Patterns in the body location of these scars as well as differences between ages and sexes were considered. Potential shark species responsible for the attacks are discussed.

Age‐related polychlorinated biphenyl dynamics in immature bull sharks (Carcharhinus leucas)

Polychlorinated biphenyls (PCBs) were quantified in liver tissues of bull sharks (Carcharhinus leucas) ranging in age from <4 wk to >3 yr. Summed values of PCBs (ΣPCBs) ranged from 310 ng/g to 22 070 ng/g (lipid wt) across age classes with ΣPCB concentrations for the youngest sharks in the present study (<4 wk; 5230 ± 2170 ng/g lipid wt) determined to not significantly differ from those quantified in >3-yr-old sharks, highlighting the extent of exposure of this young life stage to this class of persistent organic pollutants (POPs). Age normalization of PCB congener concentrations to those measured for the youngest sharks demonstrated a significant hydrophobicity (log octanol/water partition coefficient [KOW ]) effect that was indicative of maternal offloading of highly hydrophobic (log KOW ≥6.5) congeners to the youngest individuals. A distinct shift in the PCB congener profiles was also observed as these young sharks grew in size. This shift was consistent with a transition from the maternally offloaded signal to the initiation of exogenous feeding and the contributions of mechanisms including growth dilution and whole-body elimination. These results add to the growing pool of literature documenting substantially high concentrations of POPs in juvenile sharks that are most likely attributable to maternal offloading. Collectively, such results underscore the potential vulnerability of young sharks to POP exposure and pose additional concerns for shark-conservation efforts.

Comparative Feeding Ecology of Bull Sharks (Carcharhinus leucas) in the Coastal Waters of the Southwest Indian Ocean Inferred from Stable Isotope Analysis

As apex predators, sharks play an important role shaping their respective marine communities through predation and associated risk effects. Understanding the predatory dynamics of sharks within communities is, therefore, necessary to establish effective ecologically based conservation strategies. We employed non-lethal sampling methods to investigate the feeding ecology of bull sharks (Carcharhinus leucas) using stable isotope analysis within a subtropical marine community in the southwest Indian Ocean. The main objectives of this study were to investigate and compare the predatory role that sub-adult and adult bull sharks play within a top predatory teleost fish community. Bull sharks had significantly broader niche widths compared to top predatory teleost assemblages with a wide and relatively enriched range of δ13C values relative to the local marine community. This suggests that bull sharks forage from a more diverse range of δ13C sources over a wider geographical range than the predatory teleost community. Adult bull sharks appeared to exhibit a shift towards consistently higher trophic level prey from an expanded foraging range compared to sub-adults, possibly due to increased mobility linked with size. Although predatory teleost fish are also capable of substantial migrations, bull sharks may have the ability to exploit a more diverse range of habitats and appeared to prey on a wider diversity of larger prey. This suggests that bull sharks play an important predatory role within their respective marine communities and adult sharks in particular may shape and link ecological processes of a variety of marine communities over a broad range.

Sex-based spatial segregation of adult bull sharks,Carcharhinus leucas, in the New Caledonian great lagoon

Conservation of threatened large sharks and management of shark-human interactions requires an under- standing of shark occurrence and movement patterns. Here, we present the first catch, movement and behaviour data of adult bull sharks, Carcharhinus leucas, in New Caledonia. Amongst six adult C. leucas tagged with passive acous- tic tags, four females were caught in coastal waters while males were only found at an isolated oceanic barrier coral reef over 100 km from the nearest river mouth. Two females were monitored in the southern New Caledonia lagoon for 707 and 208 days respectively and displayed classical transient behaviour and sporadic short-term residency around a coastal reef bay, with movements in and out a river detected prior to spring. Adult C. leucas in New Caledonia may develop a sex-based spatial segregation with an atypical presence of adult males in oceanic environments, probably influenced by the unique estuarine-marine continuum of the New Caledonian great lagoon.

Multi‐tissue stable isotope analysis and acoustic telemetry reveal seasonal variability in the trophic interactions of juvenile bull sharks in a coastal estuary

Understanding how natural and anthropogenic drivers affect extant food webs is critical to predicting the impacts of climate change and habitat alterations on ecosystem dynamics. In the Florida Everglades, seasonal reductions in freshwater flow and precipitation lead to annual migrations of aquatic taxa from marsh habitats to deep-water refugia in estuaries. The timing and intensity of freshwater reductions, however, will be modified by ongoing ecosystem restoration and predicted climate change. Understanding the importance of seasonally pulsed resources to predators is critical to predicting the impacts of management and climate change on their populations. As with many large predators, however, it is difficult to determine to what extent predators like bull sharks (Carcharhinus leucas) in the coastal Everglades make use of prey pulses currently. We used passive acoustic telemetry to determine whether shark movements responded to the pulse of marsh prey. To investigate the possibility that sharks fed on marsh prey, we modelled the predicted dynamics of stable isotope values in bull shark blood and plasma under different assumptions of temporal variability in shark diets and physiological dynamics of tissue turnover and isotopic discrimination. Bull sharks increased their use of upstream channels during the late dry season, and although our previous work shows long-term specialization in the diets of sharks, stable isotope values suggested that some individuals adjusted their diets to take advantage of prey entering the system from the marsh, and as such this may be an important resource for the nursery. Restoration efforts are predicted to increase hydroperiods and marsh water levels, likely shifting the timing, duration and intensity of prey pulses, which could have negative consequences for the bull shark population and/or induce shifts in behaviour. Understanding the factors influencing the propensity to specialize or adopt more flexible trophic interactions will be an important step in fully understanding the ecological role of predators and how ecological roles may vary with environmental and anthropogenic changes.