Distribution, Movements, and Habitat Use of Bull Sharks (Carcharhinus Leucas, Müller and Henle 1839) in the Indian River Lagoon System, Florida PDF Download
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Author: Tobey Hayward Curtis Publisher: ISBN: Category : Languages : en Pages :
Book Description
ABSTRACT: Distribution and habitat use of the bull shark (Carcharhinus leucas) were examined using fishery-independent sampling data, tagging, and ultrasonic telemetry to assess the potential role of the Indian River Lagoon (IRL) as a nursery area for this species. Fishery-independent sampling data were compiled and synthesized to examine patterns of seasonal occurrence, spatial distribution, and habitat associations. These data provided a comprehensive overview of bull shark ecology in the study site over a span of 30 years, based on data collected from 390 individual sharks. Tagging and acoustic telemetry methods were also employed to acquire more fine-scale information on shark movements, daily activities, and habitat utilization. A total of 50 sharks were marked with conventional tags, with four fish recaptured over the course of the study. Eleven of these sharks were tagged additionally with ultrasonic pingers, ten of which were tracked manually and one of which was monitored by moored listening stations (Vemco VR2). The manual tracking data provided fine-scale information on the patterns of movements of a small number of individuals. Integration of multiple methodologies provided a more complete picture of habitat use by this important apex predator in the IRL. Bull sharks occurred over a broad range of habitats, including depths of 0.2 - 4.0 m, temperatures of 18 - 37 °C, salinities of 1 - 42 ppt, dissolved oxygen concentrations of 3 - 8 mg/L, and water clarity levels of 70 - 170 cm. In addition, they were located over seagrass, sand, and mud substrates. Overall catch-per-unit-effort was low, relative to other systems. However, higher than average catch rates were observed at power plant outfalls and near freshwater creeks. These results may prove useful to the continued management and conservation of bull shark stocks in the northwest Atlantic.
Author: Tobey Hayward Curtis Publisher: ISBN: Category : Languages : en Pages :
Book Description
ABSTRACT: Distribution and habitat use of the bull shark (Carcharhinus leucas) were examined using fishery-independent sampling data, tagging, and ultrasonic telemetry to assess the potential role of the Indian River Lagoon (IRL) as a nursery area for this species. Fishery-independent sampling data were compiled and synthesized to examine patterns of seasonal occurrence, spatial distribution, and habitat associations. These data provided a comprehensive overview of bull shark ecology in the study site over a span of 30 years, based on data collected from 390 individual sharks. Tagging and acoustic telemetry methods were also employed to acquire more fine-scale information on shark movements, daily activities, and habitat utilization. A total of 50 sharks were marked with conventional tags, with four fish recaptured over the course of the study. Eleven of these sharks were tagged additionally with ultrasonic pingers, ten of which were tracked manually and one of which was monitored by moored listening stations (Vemco VR2). The manual tracking data provided fine-scale information on the patterns of movements of a small number of individuals. Integration of multiple methodologies provided a more complete picture of habitat use by this important apex predator in the IRL. Bull sharks occurred over a broad range of habitats, including depths of 0.2 - 4.0 m, temperatures of 18 - 37 °C, salinities of 1 - 42 ppt, dissolved oxygen concentrations of 3 - 8 mg/L, and water clarity levels of 70 - 170 cm. In addition, they were located over seagrass, sand, and mud substrates. Overall catch-per-unit-effort was low, relative to other systems. However, higher than average catch rates were observed at power plant outfalls and near freshwater creeks. These results may prove useful to the continued management and conservation of bull shark stocks in the northwest Atlantic.
Author: Cheston Thomas Peterson Publisher: ISBN: Category : Ecology Languages : en Pages : 0
Book Description
Drivers of animal movement, including abiotic factors such as environmental conditions or climate and biotic factors such as species interactions and reproduction, are classic topics in ecology and relevant to both basic and applied scientific questions. Understanding phenomena such as seasonal migrations are important in fisheries management, and describing habitat use and ecological interactions is a primary goal in fisheries ecology as the field moves toward holistic, ecosystem-based approaches. Here I present the results of research investigating the drivers of movement in coastal sharks, from scales of seasonal migrations and temporal patterns of abundance to fine-scale movement of a single species as it relates to the distribution and density of its prey and predators. I used a 10 year data set of long-term fishery-independent gillnet and longline surveys to explore the effects of abiotic variables on temporal patterns of community structure of fishes and correlates of migration at two seagrass shoals off the FSU Coastal and Marine Laboratory. I examined community structure using non-metric multidimensional scaling (NMDS) with environmental fitting, compared temporal community structure using permutational multivariate analysis of variance (PERMANOVA) of monthly catch rates in both gear types, and tested for cyclicity in community structure. I also used generalized additive models (GAMs) to explore the effects of environmental variables (e.g. temperature and photoperiod) on immigration and emigration phases of dominant taxa. I found strong seasonality and cyclicity in assemblages captured by both gear types, with depauperate winter communities and diverse assemblages in warmer month - especially late summer and fall. My results suggest temperature may determine the timing of immigration and duration of the residency period of dominant taxa, including the juvenile life stages of some coastal sharks, but photoperiod may cue immigration and emigration in adults when the purpose of those migrations includes predicable reproductive functions (e.g. parturition). I found evidence of partial migration in juvenile life stages of some coastal sharks, and hypothesize that rising temperatures due to climate change may have variable effects on residency patterns over ontogeny. I conducted similar fishery-independent sampling in Apalachicola Bay from 2018 to 2020 during the summer to study habitat overlap in multiple life stages of a group of sympatric coastal sharks. I also used data shared with me by the Florida Fish and Wildlife Conservation Commission to explore the relationship of habitat use in coastal sharks to prey distribution and density. My analyses suggested this relationship may vary among species and life stage, as predation risk or environmental tolerances may drive habitat use in early life stages of some species. Prey distribution may be more important for dietary specialists. Interestingly, habitat use of species life stages with increasing reported dietary overlap appeared to converge. Using acoustic telemetry, I described movement and habitat use of bull sharks (Carcharhinus leucas), bonnetheads (Sphyrna tiburo), and gafftopsail catfish (Bagre marinus) in Apalachicola Bay and St. George Sound. I used linear mixed models (LMM) to integrate the tracking information with blue crab (Calinectes sapidus) density data from the same fishery-independent surveys conducted by FWC to explore the predator-prey dynamics of blue crabs, bonnetheads, and bull sharks. All three fishes were resident throughout the summer and were philopatric. Bull sharks used more of the habitat than bonnetheads or gafftopsail catfish. Bonnetheads mainly used seagrass habitats, while gafftopsail catfish used muddy habitats around freshwater inputs. There were relationships of size and the proportion of the acoustic array each species used, with a positive correlation of size and space used in both species of sharks and a negative correlation in gafftopsail catfish, which may be driven my differences between sexes. Bonnetheads were not detected in habitats where blue crabs were most dense, but the probability of bull shark presence was highest. Results of the LMM analyses suggested a significant negative relationship of bonnethead habitat use and bull shark presence probability, as well as a significant negative relationship of the interaction of bull shark presence and salinity (bull shark presence probability was highest at sites with the lowest average salinities). These results suggest habitat use in bonnetheads may follow predictions of optimal foraging theory and the ideal free distribution under the constraint of predation risk, which may be informative in understanding the roles of predation and prey availability in the habitat use of marine mesopredators.
Author: Hannah Calich Publisher: ISBN: Category : Languages : en Pages :
Book Description
Aquatic highly migratory species (HMS) are economically and ecologically important, however, their highly migratory nature makes them difficult to study and thus there are knowledge gaps relating to their movement and habitat use patterns. Highly migratory sharks are likely to interact with commercial longline fishing gear and be caught as target or bycatch, which can threaten their populations. Understanding the environmental factors that influence and drive the movements of highly migratory sharks may help researchers better predict their presence and subsequently identify areas where they are vulnerability to fisheries. Here I evaluated the overlap between habitat suitability and gear restricted zones for three co-occurring apex predatory sharks in the Southwest Atlantic Ocean and Gulf of Mexico (great hammerhead Sphyrna mokarran, tiger Galeocerdo cuvier, and bull sharks Carcharhinus leucas) to identify areas in this region where these species are vulnerable to and protected from commercial longline fishing. This research was accomplished in three integrated steps. First, I reviewed and summarized what is known about the environmental drivers of great hammerhead, tiger, and bull shark habitat use and movement patterns. Second, I used the results of this review to parameterize and subsequently generate habitat suitability models for these three species. Third, I used these models to spatially compare where each species' highly suitable habitat overlaps with longline gear restricted areas within the Southwest Atlantic Ocean and Gulf of Mexico, to identify regions where these species were both vulnerable to and protected from longline fishing gear. The results of this thesis have implications to the management of these species as well as for the conservation of other highly migratory aquatic species.
Author: Fiona Graham Publisher: ISBN: Category : Languages : en Pages :
Book Description
Marine protected areas (MPAs) are effective at employing ecosystem-based management as a conservation tool, however these networks of protected zones must be carefully chosen. Therefore, strategic area placement and size is crucial for the best conservation outcome. While the benefits of implementing clear protected zones are obvious for species that live sedentary lifestyles, the proportion of habitat protection that they offer to wide-ranging species is less clear. Here, we analyze satellite telemetry data in order to determine key habitat areas for three wide-ranging shark species in both the south Florida and Bahamas regions, and then quantify the level of potential habitat protection that is offered to these species by both management zones within Florida and The Bahamas EEZ. We further assess their movements and habitat use with regards to habitat preference, specifically water column depth and distance from land. The three species selected for this study are the great hammerhead (Sphyrna mokarran), tiger shark (Galeocerdo cuvier), and bull shark (Carcharhinus leucas). These species were selected primarily because, as a group, they are the apex predators in the region, are representative of the region's marine megafauna, and they rank as a conservation priority. The study area encompasses a number of different MPAs, each differing in qualities such as purpose, management agency, level of protection, and restrictions on human uses. However, for this study we are most concerned with locational boundaries and level of protection offered. More specifically, we primarily look at those areas that restrict fishing, which is a major anthropogenic threat to the study species. To accomplish this analysis, we use ArcGIS, a geographical information systems program, to overlay MPA data in the study region with analysis of satellite telemetry data. Core activity space was determined using kernel density estimates, and the 50% kernel density estimate isolpleth was considered "critical habitat." The proportion of critical habitat that is protected for each target species was then calculated by determining the percent overlap of the critical habitat area with protected areas relevant to each species. To supplement this assessment, we then evaluate habitat preference based on overlap of critical habitat use areas and physical factors, where bathymetry data is overlaid with kernel density estimate isopleths. Mean and max distance from land was also calculated for all interpolated points for each species, and all interpolated points within defined critical habitat boundaries. This analysis allowed us to quantify habitat use with regards to water column depth and distance from shore. Finally, we created separate seasonal kernel density estimates for all species for the wet and dry seasons, in order to evaluate seasonal habitat preference. Results from 26 tagged bull sharks demonstrate that Biscayne and Everglades National Parks are high use areas for these sharks, and that none of their critical habitat is currently within areas that protect the species from fishing pressure, more specifically prohibiting the landing of the species. Analysis of data from 22 tagged great hammerhead sharks illustrates that 17.88% of their critical habitat is currently protected, almost all of which is due to regulations that prohibit the landing of the species within Florida state waters. Finally, 34.74% of tagged tiger shark (n=44) critical habitat is currently protected, due to regulations that prohibit the landing of the species within Florida state waters and regulations prohibiting shark fishing within The Bahamas EEZ. Habitat preference results are consistent with our previous analysis, and show that bull sharks prefer depths of less than 10 meters and are, on average, very close to land. We found that mean distance to shore for all interpolated bull shark points was 6.4 km, and mean distance to shore for all interpolated bull shark points that lie within their defined critical habitat area was 4.3 km. Data from our 44 tagged tiger sharks demonstrated that 78.25% of their critical habitat consists of depths greater than 100 meters and mean distance from land for all points was furthest for this species, at 176.6. Average distance to shore for all points within the tiger shark critical habitat was 71.9. We found that great hammerhead critical habitat was split relatively evenly between each depth range, and their mean distance to shore for all points and for only those points within their critical habitat was 82.8km and 16.6km, respectively. Finally, seasonal kernel density estimates created for the wet and dry seasons showed that habitat use does indeed seem to vary by season. Many wide-ranging marine top predators are experiencing population declines globally (Pauly et al. 1998, Myers & Worm 2003, Hampton et al. 2005, Dulvy et al. 2008). Marine reserves are the first step toward evaluating how effective these MPAs are as conservation tools and understanding how we can work to improve them. The results from this study have valuable implications for marine conservation planning and help to develop an understanding of the current and potential level of protection for the top predator species that play integral roles in south Florida's and The Bahamas' ecosystems.
Author: Michael Philip McCallister Publisher: ISBN: Category : Shark -- Dispersal -- Florida -- Jacksonville Languages : en Pages :
Book Description
Sharks are considered top predators in many marine ecosystems, and can play an important role in structuring those communities. As a result, it is necessary to understand the factors that influence their abundance and distribution. This is particularly important as fishery managers develop fishery management plans for sharks that identify areas that serve as essential fish habitat (EFH). This includes nursery habitat where sharks are born and juveniles spend the early part of their life. However, our understanding of shark habitat use in the northeast Florida waters is limited. The goal of this thesis was to characterize the abundance and distribution of sharks in northeast Florida estuaries, and to examine the effect of abiotic and biotic factors affecting shark habitat use. A bottom longline survey conducted from 2009 - 2011 indicated that 11 shark species use the estuarine waters of northeast Florida during summer months. Atlantic sharpnose (Rhizoprionodon terraenovae), blacktip (Carcharhinus limbatus), bonnethead (Sphyrna tiburo), and sandbar sharks (Carcharhinus plumbeus) were the most abundant species and made up 87.1% of the total catch. Month, bottom water temperature, and depth were the most important factors determining the presence and abundance of these species. This study also examined the role of prey abundance in determining the abundance of Atlantic sharpnose sharks. The probability of catching an Atlantic sharpnose shark, and the abundance of Atlantic sharpnose sharks, were most influenced by site. Neither potential prey abundance nor preferred prey abundance were not significant factors effecting Atlantic sharpnose abundance. This may be a result of prey sampling not providing an accurate measure of the true availability of prey resources. Other factors, such as predation risk, may better explain habitat use patterns of Atlantic sharpnose sharks. Continued sampling will give a better understanding of the factors influencing shark habitat use in this area.
Author: Jonas Brandi Mortensen Publisher: ISBN: Category : Bull shark Languages : en Pages : 358
Book Description
Abstract : This project investigated the value and future potential of a coupled Eulerian-Lagrangian agent-based modelling approach as an alternative method of investigating the movement and habitat use of juvenile bull shark Carcharhinus leucas in small peri-urban estuaries. Through the use of the MIKE21 modelling suite (DHI), a depth-averaged two-dimensional hydro-dynamic model was developed and implemented as a means to capture the spatio-temporal variation in hydrodynamics of the semi-enclosed Tallebudgera Creek estuary. This system provides a suite of habitats comprising artificial residential canals, polyhaline and brackish creek sections in a peri-urban setting. The hydrodynamic model served as the dynamic foundation of a spatially heterogeneous agent-based model (ABM) developed for juvenile C. leucas. The movement formulation of juvenile C. leucas was represented as a kinesis search for optimal conditions, while a random walk model served as a control. The hydrodynamic model performed satisfactorily in terms of capturing the variations of key physical conditions of Tallebudgera Creek. Modelled values of surface elevation and flow dynamics were in good agreement with measured data sets. Simulated mean levels of salinity and temperature were likewise in good agreement with measured means; however, model analysis revealed a high sensitivity to increased freshwater influxes, and a delay in model response time. Three neonate and juvenile individuals of C. leucas were captured and attached with acoustic tags for tracking of movement in Tallebudgera Creek. Short-term continuous tracks of a juvenile C. leucas were successfully collected as a means to relate observed movement to out-puts of the hydrodynamic model and measurements of water quality, while consecutive data-points of animal position served as validation data for the agent-based model. Analysis of C. leucas track data revealed a high site preference for the middle reach of the system over the course of the tracking campaign, even during periods when salinity levels were 1 PSU. However, an avoidance of high salinities 27 PSU was evident. Significant movement of the animal in a downriver direction only occurred after a period of increased flow velocities and turbidity, suggesting that these parameters may play an important role in directing shark movement in conjunction with salinity. The agent-based models in their current developmental stage performed unsatisfactorily in capturing observed movement, and their predictive ability was generally poor. The current ABM formulation of C. leucas movement is therefore deemed insufficient to capture the observed pattern of behaviour. However, unforseen technical difficulties originating from the narrow and shallow nature of the Tallebudgera Creek system prevented a full assessment of the ABM results. Despite current technical issues that were impracticable to be resolved under the available timeframe, this study represents a first attempt to construct and implement agent-based modelling to investigate bull shark movement and habitat use in a spatially and temporally dynamic hydrologic environment. It is predicted that once these technical difficulties are overcome, agent-based modelling as a research tool holds great promise for future investigation of the habitat ecology of C. leucas to benefit its conservation and management.
Author: Tobey Hayward Curtis
Author: Tobey Hayward Curtis
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Author: 
Author: Cheston Thomas Peterson
Author: Jennifer Brooke Shipley
Author: Hannah Calich
Author: Fiona Graham
Author: Michael Philip McCallister
Author: Jonas Brandi Mortensen
Author: Frank Joseph Schwartz