Bimini Biological Field Station

Bahamas

Bimini Biological Field Station

Bahamas
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Kessel S.T.,University of Windsor | Hussey N.E.,University of Windsor | Webber D.M.,Vemco Ltd. | Gruber S.H.,Bimini Biological Field Station | And 4 more authors.
Animal Biotelemetry | Year: 2015

Background: When employing acoustic telemetry to study aquatic species, understanding the functional dynamics of the monitoring system is essential for effective study design, data interpretation, and analysis. Typically, researchers are concerned with maximum effective detection range and consequently tend to employ the largest most powerful tags the study species can carry without considerable energetic burden. In ideal acoustic conditions of low ambient noise environments, low attenuation, and reflective structure, higher powered tags can be detected at larger distances from the receiver, but they can also be subject to the phenomenon 'Close Proximity Detection Interference' (CPDI). This occurs when reflective barriers, such as a calm water surface and/or hard substrate, result in strong transmission echoes that interfere with the transmission sequence. As a result, transmissions in close proximity to the receiver are not effectively decoded and logged. Results: CPDI was assessed from the results of three detection range tests conducted using the Vemco 69kHz telemetry system in three contrasting study systems: a sheltered marine Arctic embayment, a temperate freshwater lake, and an exposed marine sub-tropical reef line. For the Arctic embayment, CPDI was absent with the lower power V9 tag (90% of transmissions received at 55m) but was recorded for the V13 tag and was most prevalent for the highest power V16 tag (18% and 8% of transmissions received at 55m, respectively). Comparing V16 tag detection profiles between study systems, CPDI was evident in the low ambient noise Arctic embayment and temperate freshwater lake (highest transmission proportions recorded at 370 and 207m, respectively) but was absent on the high ambient noise sub-tropical reef line. Functional examples highlight the ways in which CPDI can affect different study designs if not acknowledged or accounted for. Conclusions: CPDI was shown to be the most prominent in low ambient noise study systems and should be considered when choosing tag type/power during study design. If unaccounted for, CPDI could lead to misinterpretation during the analysis of acoustic telemetry data. The identification of CPDI highlights the complexities associated with the functionality of acoustic telemetry systems and supports recommendations for thorough detection range testing. © 2015 Kessel et al.; licensee BioMed Central.


White E.R.,University of California at Davis | Nagy J.D.,Arizona State University | Gruber S.H.,Bimini Biological Field Station
Biology Direct | Year: 2015

Background: Long-lived marine megavertebrates (e.g. sharks, turtles, mammals, and seabirds) are inherently vulnerable to anthropogenic mortality. Although some mathematical models have been applied successfully to manage these animals, more detailed treatments are often needed to assess potential drivers of population dynamics. In particular, factors such as age-structure, density-dependent feedbacks on reproduction, and demographic stochasticity are important for understanding population trends, but are often difficult to assess. Lemon sharks (Negaprion brevirostris) have a pelagic adult phase that makes them logistically difficult to study. However, juveniles use coastal nursery areas where their densities can be high. Results: We use a stage-structured, Markov-chain stochastic model to describe lemon shark population dynamics from a 17-year longitudinal dataset at a coastal nursery area at Bimini, Bahamas. We found that the interaction between delayed breeding, density-dependence, and demographic stochasticity accounts for 33 to 49% of the variance in population size. Conclusions: Demographic stochasticity contributed all random effects in this model, suggesting that the existence of unmodeled environmental factors may be driving the majority of interannual population fluctuations. In addition, we are able to use our model to estimate the natural mortality rate of older age classes of lemon sharks that are difficult to study. Further, we use our model to examine what effect the length of a time series plays on deciphering ecological patterns. We find that-even with a relatively long time series-our sampling still misses important rare events. Our approach can be used more broadly to infer population dynamics of other large vertebrates in which age structure and demographic stochasticity are important. Reviewers: This article was reviewed by Yang Kuang, Christine Jacob, and Ollivier Hyrien. © 2014 White et al.; licensee BioMed Central Ltd.


Reyier E.A.,Kennedy Space Center Ecological Program and InoMedic Health Applications | Franks B.R.,Florida Southern College | Chapman D.D.,State University of New York at Stony Brook | Scheidt D.M.,Kennedy Space Center Ecological Program and InoMedic Health Applications | And 2 more authors.
PLoS ONE | Year: 2014

Resolving the geographic extent and timing of coastal shark migrations, as well as their environmental cues, is essential for refining shark management strategies in anticipation of increasing anthropogenic stressors to coastal ecosystems. We employed a regional-scale passive acoustic telemetry array encompassing 300 km of the east Florida coast to assess what factors influence site fidelity of juvenile lemon sharks (Negaprion brevirostris) to an exposed coastal nursery at Cape Canaveral, and to document the timing and rate of their seasonal migrations. Movements of 54 juvenile lemon sharks were monitored for three years with individuals tracked for up to 751 days. While most sharks demonstrated site fidelity to the Cape Canaveral region December through February under typical winter water temperatures, historically extreme declines in ocean temperature were accompanied by rapid and often temporary, southward displacements of up to 190 km along the Florida east coast. From late February through April each year, most sharks initiated a northward migration at speeds of up to 64 km day-1 with several individuals then detected in compatible estuarine telemetry arrays in Georgia and South Carolina up to 472 km from release locations. Nineteen sharks returned for a second or even third consecutive winter, thus demonstrating strong seasonal philopatry to the Cape Canaveral region. The long distance movements and habitat associations of immature lemon sharks along the US southeast coast contrast sharply with the natal site fidelity observed in this species at other sites in the western Atlantic Ocean. These findings validate the existing multi-state management strategies now in place. Results also affirm the value of collaborative passive arrays for resolving seasonal movements and habitat preferences of migratory coastal shark species not easily studied with other tagging techniques. © 2014 Reyier et al.


Guttridge T.L.,University of Leeds | Gruber S.H.,Bimini Biological Field Station | Krause J.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Sims D.W.,Marine Biological Association of The United Kingdom | Sims D.W.,University of Plymouth
PLoS ONE | Year: 2010

Group behaviours are widespread among fish but comparatively little is known about the interactions between free-ranging individuals and how these might change across different spatio-temporal scales. This is largely due to the difficulty of observing wild fish groups directly underwater over long enough time periods to quantify group structure and individual associations. Here we describe the use of a novel technology, an animal-borne acoustic proximity receiver that records close-spatial associations between free-ranging fish by detection of acoustic signals emitted from transmitters on other individuals. Validation trials, held within enclosures in the natural environment, on juvenile lemon sharks Negaprion brevirostris fitted with external receivers and transmitters, showed receivers logged interactions between individuals regularly when sharks were within 4 m (∼4 body lengths) of each other, but rarely when at 10 m distance. A field trial lasting 17 days with 5 juvenile lemon sharks implanted with proximity receivers showed one receiver successfully recorded association data, demonstrating this shark associated with 9 other juvenile lemon sharks on 128 occasions. This study describes the use of acoustic underwater proximity receivers to quantify interactions among wild sharks, setting the scene for new advances in understanding the social behaviours of marine animals. © 2010 Guttridge et al.


Guttridge T.L.,University of Leeds | Gruber S.H.,Bimini Biological Field Station | DiBattista J.D.,Hawaii Institute of Marine Biology | Feldheim K.A.,Pritzker Laboratory for Molecular Systematics and Evolution | And 3 more authors.
Marine Ecology Progress Series | Year: 2011

For marine predators there is a paucity of studies on social behaviour, and even fewer studies have quantified interactions between individuals. In the present study, we looked at the social structure and leadership of free-ranging juvenile lemon shark Negaprion brevirostris in a known aggregation site, Bimini, the Bahamas. Observations of these sharks were made from towers placed in a mangrove inlet, where clear, shallow, protected waters made it possible to record group compositions of externally colour-code tagged wild juvenile lemon sharks. Thirty-eight different individual sharks were observed to use the area over a 2 yr period. Results show repeated social interactions suggestive of active partner preference. In addition, we found that group structure was mostly explained by body length, and possibly by preference for relatives but not by sex. Finally, we observed that some sharks led more groups than others and that those lead individuals were usually larger than those following them. This study quantifies the social structure of a free-ranging shark population and provides novel insights into the social behaviour of juvenile sharks. © Inter-Research 2011.


Digirolamo A.L.,Florida Fish And Wildlife Conservation Commission | Gruber S.H.,Bimini Biological Field Station | Gruber S.H.,University of Miami | Pomory C.,University of West Florida | Bennett W.A.,University of West Florida
Journal of Fish Biology | Year: 2012

The relatively complex pattern of temperature selection exhibited by juvenile lemon sharks Negaprion brevirostris in the North Sound differed markedly from many previously described responses of fish preferenda. Thermal data demonstrated that juvenile N. brevirostris did not attempt to behaviourally maintain a constant eccritic temperature. Rather, juveniles selected progressively warmer temperatures throughout the day until reaching the highest temperatures available, and then moved to cooler temperatures during late evening and early morning hours. It is possible that by exploiting habitat thermal heterogeneity juvenile N. brevirostris prolong activities such as feeding or digestion well into the cooler parts of the evening. The complex pattern of temperature occupation by juvenile N. brevirostris within the thermally heterogeneous North Sound nursery is probably linked to key daily activities such as prey capture, predator avoidance and digestive efficiency. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.


O'Connell C.P.,Coastal Carolina University | Abel D.C.,Coastal Carolina University | Gruber S.H.,Bimini Biological Field Station | Stroud E.M.,Oak Technologies | Rice P.H.,Florida College
Ocean and Coastal Management | Year: 2011

Beach nets are preventative devices used to minimize interactions between potentially harmful sharks and unsuspecting swimmers. Quantitative studies demonstrated that beach nets drastically reduced local elasmobranch populations, as well as caused considerable bycatch mortality. For this experiment, a beach net-like device was constructed and the behaviors of six juvenile lemon sharks (Negaprion brevirostris) were analyzed. Induced by olfactory and gustatory cues, sharks were given the choice to swim through a magnetic or control opening in the net. In the first trial, all six sharks avoided the magnetic region and significantly preferred to swim through the control region of the fence. The magnetic stimulus no longer affected the swimming behavior of three sharks retested after resting 24 h. Results from the retested sharks were correlated with those from repeated tonic immobility trials, which demonstrated a linear decrease in sensitivity to repeated magnetic stimulation. This study serves as a baseline experiment demonstrating that permanent magnets may substantially decrease elasmobranch mortality within beach nets. © 2010 Elsevier Ltd.


O'Connell C.P.,University of Massachusetts Dartmouth | Guttridge T.L.,Bimini Biological Field Station | Guttridge T.L.,University of Cardiff | Gruber S.H.,Bimini Biological Field Station | And 4 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2014

The ability of elasmobranchs to orient to weak electromagnetic fields is well documented. Recently, scientists have employed the use of strong electrosensory stimuli, such as permanent magnets, as a means to evaluate the repellent responses of elasmobranchs and assess the utility of these materials for bycatch repellent technologies. However, several studies have produced contrasting results both between and within species. To explain these results, we hypothesized that conditions leading to vision loss (i.e. turbid water) may be a factor affecting electrosensory repellent success. To simulate a visually deprived environment, the nictitating membranes of juvenile lemon sharks (Negaprion brevirostris) were temporarily sutured closed and the behavioral responses of sharks towards a magnetic apparatus were observed in a pen within the shallows of Bimini, Bahamas. Results demonstrate that the magnet-associated behavior of visually deprived sharks significantly differed from control sharks in regard to: (1) avoidance distance, (2) visit quantity prior to first entrance through the magnet zone, and (3) total entrances/total visits. These findings suggest context-dependent switching, where elasmobranchs may exhibit a heightened reliance on their electrosensory system when the extent of their visual range is reduced. These findings also provide insight into favorable environments (e.g. estuary or other coastal ecosystems) and applications (e.g. inshore fisheries and beach nets) that may yield more consistent and successful future implementations of electrosensory repellents for sharks. © 2014 Elsevier B.V.


Newman S.P.,University of Plymouth | Newman S.P.,Northumbria University | Handy R.D.,University of Plymouth | Gruber S.H.,Bimini Biological Field Station | Gruber S.H.,University of Miami
Environmental Biology of Fishes | Year: 2012

Ontogenetic variations in shark diet are often qualitatively inferred from dietary analysis and hindered by high levels of unidentified prey or small sample sizes. This study focused on nursery bound lemon sharks (Negaprion brevirostris, n = 396), enabling some control over the confounding variables of prey choice associated with ontogeny. Nursery bound lemon sharks exhibited weak ontogenetic variation in dietary composition with high levels of dietary overlap. Variation in prey preference of lemon sharks with ontogeny was complex, but revealed a continuous shift from predominantly opportunistic benthic foraging as neonates to more selective piscivory with increasing shark size while in the nursery. Lemon sharks demonstrated a discrete ontogenetic shift in the number of prey consumed and stomach content weight (Kruskal-Wallis tests p < 0.01), as well as prey size (ANOVA, p < 0. 001). All sizes of sharks exhibited positive size selection of prey (Mann-Whitney U tests, p < 0. 01). However, the lack of size preference by all but the largest lemon sharks for their major prey (yellowfin mojarra, Gerres cinereus), suggests neonate sharks, while capable of occasionally foraging on large prey, are relatively inept opportunistic foragers. This was evident in high diet breadth, low diversity of consumed prey and lower trophic level than larger sharks. This study represents the first quantitative analysis of ontogenetic variation in prey preference and size selection in sharks, indicating a flexible foraging tactic in lemon sharks and the importance of hunting ability and predator size in prey choice. © 2011 Springer Science+Business Media B.V.


O'Connell C.P.,University of Massachusetts Dartmouth | O'Connell C.P.,OSeas Conservation Foundation | Hyun S.-Y.,University of Massachusetts Dartmouth | Gruber S.H.,Bimini Biological Field Station | He P.,University of Massachusetts Dartmouth
Endangered Species Research | Year: 2015

The great hammerhead shark Sphyrna mokarran is an endangered species that is exposed to several sources of anthropogenic mortality, including beach nets. Although not a major contributor to S. mokarran mortality, beach nets are utilized in several locations to minimize the potential harmful interaction between sharks and beachgoers. To address this mortality, permanent magnets have been employed to determine if these materials can deter sharks away from netted areas. The present study examined the effects of barium-ferrite (BaFe12O19) permanent magnets on S. mokarran behavior under several environmental and biological conditions. In the bait experiment, feeding frequency significantly decreased and avoidance frequency significantly increased with the magnet treatment, with exposure quantity yielding an increase in feeding frequency, although this effect was not statistically significant. For the barrier experiment, entrance frequency significantly decreased and avoidance and pass-around frequencies significantly increased with the magnet treatment, with heterospecific density also being a significant pre - dictor of entrance frequency. The findings demonstrate how permanent magnets can modify S. mokarran behavior and how this behavior is modified based on situational context. Since several other sphyrnid species are caught in beach nets more frequently than S. mokarran (e.g. scalloped hammerheads S. lewini), the present results may serve as a model for these other sphyrnid species and illustrate the potential conservation implications of future magnetic deterrent barrier technologies. © The authors 2015.

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