Sicklefin Lemon Sharks Negaprion Acutidens Research Articles

Thermally insensitive physiological performance allows neonatal sharks to use coastal habitats as nursery areas

Coastal sharks can use shallow, nearshore habitats as nursery areas, which is a behaviour that may increase fitness. The ecological benefits of shark nursery areas are well studied; yet the physiological mechanisms that enable sharks to exploit coastal habitats, especially those that experience extreme and dynamic temperatures, remain understudied. We hypothesised that neonatal sharks are able to use thermally dynamic coastal habitats as nursery areas because temperature does not strongly affect their physiology. To test this hypothesis, we defined patterns of nursery area use and temperature-dependent physiological performance in 2 reef shark species. First, we determined whether 10 sites around the island of Moorea, French Polynesia, satisfied nursery area criteria for neonate populations of blacktip reef sharks Carcharhinus melanopterus and sicklefin lemon sharks Negaprion acutidens using 5 consecutive years of abundance surveys. We then quantified effects of thermal exposure in situ on growth in recaptured individuals and quantified the temperature dependence of metabolic rate ex situ using respirometry. We found several potential C. melanopterus nursery areas, but during different sampling years, and identified 1 N. acutidens nursery area that remained consistent during the entire 5 yr study. In support of our hypothesis, growth and metabolic performance were not strongly affected by temperature in either species. Thus, thermally insensitive physiological performance may be a trait that elasmobranchs exhibit in thermally variable coastal habitats, including shark nursery areas. Together, this approach demonstrates how physiological and ecological concepts complement each other to improve our understanding of nursery area use in coastal shark populations.

At the Turn of the Tide: Space Use and Habitat Partitioning in Two Sympatric Shark Species Is Driven by Tidal Phase

Coexistence of ecologically similar species occupying the same geographic location (sympatry) poses questions regarding how their populations persist without leading to competitive exclusion. There is increasing evidence to show that micro-variations in habitat use may promote coexistence through minimising direct competition for space and resources. We used two sympatric marine predators that show high fidelity to a small, remote coral atoll as a model to investigate how temporally dynamic partitioning of space use may promote coexistence. Using novel methods (difference network analysis and dynamic space occupancy analysis), we revealed that even though blacktip reef sharks Carcharhinus melanopterus and sicklefin lemon sharks Negaprion acutidens both show focused use of the same atoll habitats, the spatio-temporal dynamics of their use was partitioned such that they only shared the same microhabitats 26% of the time. Moreover, the degree of overlap was strongly influenced by the tidal cycle, peaking at ~35% at higher tides as both species appear to target similar intertidal micro-habitats despite the increase in available space. Our work provides a rare example of how two marine predators with similar ecological roles and habitat preferences may coexist in the same place through dynamic segregation of habitat use in space and time, potentially reflecting adaptive behavioural traits for minimising interactions. The strong influence of small tidal variation on species habitat use and partitioning also raises concerns over how atoll ecosystem dynamics may be influenced by sea level rises that could alter tidal dynamics.

Size frequency, dispersal distances and variable growth rates of young sharks in a multi-species aggregation.

During a mark-recapture survey from November 2014 until April 2017, 333 neonatal and juvenile blacktip reef sharks Carcharhinus melanopterus and 302 neonatal and juvenile sicklefin lemon sharks Negaprion acutidens were tagged and measured at the uninhabited and isolated St. Joseph Atoll (Republic of Seychelles). Both species demonstrated seasonal reproductive synchronicity and relatively large sizes at birth. Despite the extended times at liberty > 2.5 years, the majority of recaptures were found in close proximity to the initial tagging location (< 500 m). Annual growth rates of C. melanopterus (n = 24) and N. acutidens (n = 62) ranged from 6.6 to 31.7 cm year-1 (mean ± SE; 16.2 ± 1.2 cm year-1 ) and 0.2 to 32.2 cm year-1 (11.8 ± 1 cm year-1 ), respectively and are to date the most variable ever recorded in wild juvenile sharks. High abundances of both species coupled with long-term and repeated recaptures are indicative of a habitat where juveniles can reside for their first years of life. However, large variability in annual growth rates in both species may suggest high intra and interspecific competition induced by a possibly resource limited, isolated habitat.

Baited Remote Underwater Video surveys undercount sharks at high densities: insights from full-spherical camera technologies

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 585:113-121 (2017) - DOI: https://doi.org/10.3354/meps12395 Baited Remote Underwater Video surveys undercount sharks at high densities: insights from full-spherical camera technologies James P. Kilfoil1,*, Aaron J. Wirsing2, Matthew D. Campbell3, Jeremy J. Kiszka1, Kirk R. Gastrich1, Michael R. Heithaus1, Yuying Zhang1, Mark E. Bond1 1Department of Biological Sciences, Florida International University, North Miami, FL 33181, USA 2School of Environmental and Forest Sciences, University of Washington, Seattle, WA 98195, USA 3National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS 39567, USA *Corresponding author: jkilf001@fiu.edu ABSTRACT: Video surveys are an essential tool for monitoring marine communities. Their use to study elasmobranch populations has dramatically increased over the last decade. However, the restricted field-of-view (FOV) of traditional cameras in these surveys may bias abundance estimates in a number of ways, including saturation at high densities and low detection probability for rare or cryptic species. This study investigated these potential biases using newly developed full-spherical (FS) camera technology. A comparison of 35 Baited Remote Underwater Video surveys (BRUVs), using both FS and traditional cameras, was conducted from July to August 2016 in shallow waters (0.4 to 8.5 m) of Tetiaroa, French Polynesia. Both blacktip reef Carcharhinus melanopterus and sicklefin lemon sharks Negaprion acutidens were quantified from traditional cameras using MaxN and MeanCount methods. These estimates were then regressed against FS cameras counts, which were assumed to more accurately represent site abundance, to test for gear saturation. Detection probabilities of the traditional and FS cameras were assessed using a Bayesian binomial model, with uninformed-uniform priors. Results indicated a significant effect of gear saturation for standard BRUVs as counts on FS cameras increased, regardless of the metric used. Furthermore, traditional cameras had a significantly lower detection probability (mean ± 2 SD: 69.88 ± 0.008%) than FS cameras (81.20 ± 0.007%). Our findings show that traditional cameras are unlikely to adequately discriminate differences in shark relative abundance at high densities. Therefore, standard BRUV techniques that use restricted FOV cameras are likely limited in their ability to provide accurate information to managers once populations have reached particular thresholds of abundance. KEY WORDS: 360° cameras · Detectability · Elasmobranchs · Monitoring · Video surveys Full text in pdf format Supplementary material PreviousNextCite this article as: Kilfoil JP, Wirsing AJ, Campbell MD, Kiszka JJ and others (2017) Baited Remote Underwater Video surveys undercount sharks at high densities: insights from full-spherical camera technologies. Mar Ecol Prog Ser 585:113-121. https://doi.org/10.3354/meps12395 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 585. Online publication date: December 22, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Population structure of the sicklefin lemon shark Negaprion acutidens within the Curieuse Marine National Park, Seychelles

This study produced the first data on population parameters for sicklefin lemon shark Negaprion acutidens at the granitic Seychelles Islands, adding to a limited catalogue of species information. Juveniles at a site in the Curieuse Marine National Park were tagged over two periods, in 2014–2015 and 2015–2016, with measurements of length (precaudal, fork and total) and weight, sex, and state of the umbilical opening recorded. Recapture data were used to calculate growth rates and population size. Mean annual growth rate was 5.40 cm y–1. A mean size at birth of 62.5 cm TL is in line with previous assessments of the species. Population-size estimates were similar for the two sampling periods (comprising 311 and 255 individuals) and higher than anticipated. Movements to outside the lagoon were recorded for early ages, and this, combined with weight loss and a reduction in condition factor as displayed in several individuals, suggests that the study area alone could not support the large number of sharks pupped yearly.

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.

Apparent resource partitioning and trophic structure of large-bodied marine predators in a relatively pristine seagrass ecosystem

Large predators often play important roles in structuring marine communities. To understand the role that these predators play in ecosystems, it is crucial to have knowledge of their interactions and the degree to which their trophic roles are complementary or redundant among species. We used stable isotope analysis to examine the isotopic niche overlap of dolphins Tursiops cf. aduncus, large sharks (>1.5 m total length), and smaller elasmobranchs (sharks and batoids) in the relatively pristine seagrass community of Shark Bay, Australia. Dolphins and large sharks differed in their mean isotopic values for ! 13 C and ! 15 N, and each group occupied a rela- tively unique area in isotopic niche space. The standard ellipse areas (SEAc; based on bivariate standard deviations) of dolphins, large sharks, small sharks, and rays did not overlap. Tiger sharks Galeocerdo cuvier had the highest ! 15 N values, although the mean ! 13 C and ! 15 N values of pigeye sharks Carcharhinus amboinensis were similar. Other large sharks (e.g. sicklefin lemon sharks Negaprion acutidens and sandbar sharks Carcharhinus plumbeus) and dolphins appeared to feed at slightly lower trophic levels than tiger sharks. In this seagrass-dominated ecosystem, seagrass- derived carbon appears to be more important for elasmobranchs than it is for dolphins. Habitat use patterns did not correlate well with the sources of productivity supporting diets, suggesting that habitat use patterns may not necessarily be reflective of the resource pools supporting a popula- tion and highlights the importance of detailed datasets on trophic interactions for elucidating the ecological roles of predators.

Spatial behaviour and site fidelity of the sicklefin lemon shark Negaprion acutidens in a remote Indian Ocean atoll

Understanding the movement behaviour of any species is important for developing species-specific management and conservation measures. In recent years, the sicklefin lemon shark Negaprion acutidens has shown rapid range reductions and has even disappeared altogether in certain areas. In this study, the area use patterns and site fidelity of the N. acutidens were assessed at the St. Joseph Atoll in the Seychelles. Passive acoustic telemetry methods were employed to monitor the movements of 19 tagged individuals for 1 year. Area use within the lagoon of the atoll was found to be highly restricted, with individuals typically utilising a small portion of the available area throughout the year. A high-use zone was apparent in the south-east of the atoll’s lagoon, which was shared by many of the monitored individuals. Fidelity to the study site was found to be extremely high, with the 79 % of tagged N. acutidens still present in the atoll at the end of the study. Individuals displayed both diel and tidal movements between the lagoon and surrounding habitats. The restricted area use and high site fidelity observed in this study highlight both the vulnerability of this species to rapid over exploitation and importance of remote habitats such as the St. Joseph Atoll in their future conservation. The results obtained here can be used to inform management decisions regarding the development and utilisation of similar atoll environments throughout the species’ range.

Baiting sharks for marine tourism: Comment on Clua et al. (2010)

A recent study by Clua et al. (2010; Mar Ecol Prog Ser 414:257-266) that looks at the behavioural response of sicklefin lemon sharks Negaprion acutidens to underwater feeding for eco- tourism purposes has a number of methodological and semantic problems that complicate the evalu- ation of the results and raise questions about the conclusions. Main issues are the lack of a control, the use of non-defined terms to characterize observed behaviours, and statements not supported by data. Unwarranted conclusions include the notion that behavioural changes were caused by the human interference, the link between intraspecific aggression and the feeding process, and the loss of genetic variability as a consequence of the aggregating effect of shark feeding.

Effects of provisioning on shark behaviour: Reply to Brunnschweiler &amp; McKenzie (2010)

Brunnschweiler & McKenzie (2010; Mar Ecol Prog Ser 420:283-284) expressed reserva- tions over the findings of Clua et al. (2010; Mar Ecol Prog Ser 414:257-266), mostly related to the lack of a reference site or a control group in the methodology. In our study, we distinguished between 39 individuals of sicklefin lemon sharks Negaprion acutidens, mainly based on photo-identification. Our study was based on the field-survey approach, with time (a continuous variable) as the source of vari- ation, and thus a control group was not necessary. We provide here additional data that support the notion that abundance of lemon sharks on the provisioning site was increasing, both in their number and fidelity. We maintain our conclusion that sicklefin lemon shark provisioning off Moorea Island can continue, but should be more intensely controlled.

Behavioural response of sicklefin lemon sharks Negaprion acutidens to underwater feeding for ecotourism purposes

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 414:257-266 (2010) - DOI: https://doi.org/10.3354/meps08746 Behavioural response of sicklefin lemon sharks Negaprion acutidens to underwater feeding for ecotourism purposes Eric Clua1,2,*, Nicolas Buray3, Pierre Legendre4, Johann Mourier3, Serge Planes3 1Secretariat of the Pacific Community, BPD5, 98848 Noumea, New Caledonia 2Ministère de l’Agriculture et de la Pêche, 251 Rue de Vaugirard, Paris 15, France 3Centre de Recherches Insulaires et Observatoire de l’Environnement (CRIOBE – USR 3278 EPHE CNRS), BP 1013, 98729 Moorea, French Polynesia 4Département de sciences biologiques, Université de Montréal, CP 6128, succursale Centreville, Montréal, Québec H3C 3J7, Canada *Email: ericc@spc.int ABSTRACT: The feeding of marine predators is a popular means by which tourists and tour operators can facilitate close observation and interaction with wildlife. Shark-feeding has become the most developed provisioning activity around the world, despite its controversial nature. Amongst other detrimental effects, the long-term aggregation of sharks can modify the natural behaviour of the animals, potentially increase their aggression toward humans, and favour inbreeding. During 949 diving surveys conducted over 44 mo, we investigated the ecology and residence patterns of 36 photo-identified adult sicklefin lemon sharks Negaprion acutidens. The group contained 20 females and 16 males. From this long-term survey, we identified 5 different behavioural groups that we described as ‘new sharks’ (7), ‘missing sharks’ (4), ‘resident sharks’ (13), ‘unpredictable sharks’ (5) and ‘ghost sharks’ (7). In spite of movements in and out of the area by some males and females, which were probably related to mating, the general trend was that residency significantly increased during the study, particularly in males, showing a risk of inbreeding due to the reduction of shark mobility. Intra- and interspecific aggression was also witnessed, leading to an increased risk of potentially severe bites to humans. Our findings suggest the need for a revision of the legal framework of the provisioning activity in French Polynesia, which could include a yearly closure period to decrease shark behavioural modifications due to long-term shark-feeding activities. KEY WORDS: Shark-feeding · Provisioning · Human disturbance · Behaviour · Site residence Full text in pdf format See Comment and Reply Comment on this article PreviousNextCite this article as: Clua E, Buray N, Legendre P, Mourier J, Planes S (2010) Behavioural response of sicklefin lemon sharks Negaprion acutidens to underwater feeding for ecotourism purposes. Mar Ecol Prog Ser 414:257-266. https://doi.org/10.3354/meps08746Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 414. Online publication date: September 13, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.