Movement, Residency and Habitat Use of Pelagic Sharks in Spencer Gulf

Movement, Residency and Habitat Use of Pelagic Sharks in Spencer Gulf
Author: Paul J. Rogers
Publisher:
Total Pages: 103
Release: 2018
Genre: Carcharhinus
ISBN: 9781876007096

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"The report focuses on the movement dynamics of two pelagic sharks, the White Shark (Carcharadon carcharias) and Bronze Whaler (Carcharinhus brachyurus), in South Australia. Specific aims were to: (1) determine if aquaculture activities correlated with patterns on fidelity and migration; and (2) assess and compare the use of natural foraging areas and areas used during human marine activities. Additional objectives included the development of: industry guidelines for removal and release of pelagic sharks from finfish aquaculture pontoons, and surveys to collect baseline information on perceptions of shark associations with aquaculture and other marine activities. Key outcomes of the project include provision of advice to marine policy-makers regarding overlaps between sharks, marine industries and areas used during community activities (including marine parks). This project addressed important research and management questions that existed for over a decade" -- from Executive Summary.

Migration, Habitat Use, and Predator-prey Dynamics of Coastal Sharks in the Northeast Gulf of Mexico

Migration, Habitat Use, and Predator-prey Dynamics of Coastal Sharks in the Northeast Gulf of Mexico
Author: Cheston Thomas Peterson
Publisher:
Total Pages: 0
Release: 2021
Genre: Ecology
ISBN:

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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.

Offshore Survey of the Biodiversity, Distributions and Habitat Use of Pelagic Sharks in the Great Australian Bight

Offshore Survey of the Biodiversity, Distributions and Habitat Use of Pelagic Sharks in the Great Australian Bight
Author: Paul J. Rogers
Publisher:
Total Pages: 77
Release: 2016
Genre: Marine ecology
ISBN:

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"The Great Australian Bight pelagic ecosystem encompasses distributions of several highly migratory marine predator species with national and international conservation and management significance ... Project 4 of the collaborative Great Australian Bight Research Program, entitled Ecology of iconic species and apex predators, had obejctives that included describing key habitats of the pelagic shark assemblages in the Great Australian Bight. An offshore pelagic survey was conducted on the FPV Southern Ranger and represented the first dedicated effort to investigate the pelagic shark assemblage in continental shelf-break, slope and near slope oceanic habitats in the Great Australian Bight"--Executive summary.

Identifying Suitable Habitat for Three Highly Migratory Sharks (Great Hammerhead, Tiger, and Bull) and Assessing Their Spatial Vulnerability to Commercial Longline Fishing in the Southwest Atlantic Ocean and Gulf of Mexico

Identifying Suitable Habitat for Three Highly Migratory Sharks (Great Hammerhead, Tiger, and Bull) and Assessing Their Spatial Vulnerability to Commercial Longline Fishing in the Southwest Atlantic Ocean and Gulf of Mexico
Author: Hannah Calich
Publisher:
Total Pages:
Release: 2016
Genre:
ISBN:

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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.

Movement Patterns and Habitat Use of Scalloped Hammerhead Sharks (Sphyrna Lewini) in the Galapagos Islands

Movement Patterns and Habitat Use of Scalloped Hammerhead Sharks (Sphyrna Lewini) in the Galapagos Islands
Author: James Thomas Ketchum
Publisher:
Total Pages:
Release: 2011
Genre:
ISBN: 9781267238986

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Movements of marine predators like sharks are controlled by multiple external and internal factors, and bounded within a home range where all behavioral activities necessary for their survival take place. Sharks are present in great numbers at the Galapagos Marine Reserve (GMR), but little is known about them. In Chapter One, we analyze movements of scalloped hammerheads in the GMR, examine diel and seasonal movements, and environmental factors. We tagged 134 scalloped hammerhead sharks with pingers (2006- 2010). Sharks were only detected at Darwin, Wolf, Roca Redonda, and Seymour in the GMR. Hammerheads formed large schools at Darwin and Wolf during the day, but dispersed at night. They stayed longer at Wolf in the warm period and were absent from March to June. Wolf was the center of foraging excursions and Darwin a 'stepping stone' for long-distance migration. In Chapter Two, we study the movements of hammerheads around an oceanic island and the environmental characteristics of their activity spaces. We tracked seven scalloped hammerhead sharks for 19 to 96 h. A measure of preference was quantified at the level of environments (e.g. hotspot, nearshore, island base, and trenches). Hammerheads remained shallower, but moved faster during the warm season, and stayed deeper and moved slower in the cold season. Home ranges of hammerheads varied in size, but no significant differences between the cold and warm seasons. Hammerheads preferred the eastern side of Wolf Island, a refuging habitat, and the nearshore and trenches environments, possible foraging habitat. Hammerheads move near and above the thermocline, to thermoregulate, feed or digest. Density gradients are possibly used for orientation. In Chapter Three, we define movements of a marine predator, examine their value as conservation tools, evaluate their vulnerability and persistence, and design protected pelagic environments. The movements of scalloped hammerheads were on insular, inter-island, and oceanic spatial scales. Seascape species remained at localized hotspots around islands and moved outside the boundaries of MPAs. Persistence of seascape species was highest in large reserves and vulnerability was low between nearby reserves. We propose (1) a network of small marine reserves within the GMR, (2) a network of large reserves in the eastern tropical Pacific (ETP), and (3) a large 'special marine protected area (MPA)' in the ETP.

Distribution, Movements, and Habitat Use of Bull Sharks (Carcharhinus Leucas, Müller and Henle 1839) in the Indian River Lagoon System, Florida

Distribution, Movements, and Habitat Use of Bull Sharks (Carcharhinus Leucas, Müller and Henle 1839) in the Indian River Lagoon System, Florida
Author: Tobey Hayward Curtis
Publisher:
Total Pages:
Release: 2008
Genre:
ISBN:

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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.

Movement Patterns and Habitat Use of Three Species of Juvenile Sharks Within Buck Island Reef National Monument, St. Croix, United States Virgin Islands

Movement Patterns and Habitat Use of Three Species of Juvenile Sharks Within Buck Island Reef National Monument, St. Croix, United States Virgin Islands
Author: Maggie Rios
Publisher:
Total Pages: 78
Release: 2019
Genre: Sharks
ISBN:

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Nurseries are vital areas that sharks utilize during the beginning stages of their lives. Nursery habitats are characterized by shallow coastal areas that provide protection from predation by adult sharks, and waters that have high food supplies. Understanding how sharks move throughout and utilize different nursery microhabitats is vital for conservation efforts. In this thesis, three species of juvenile sharks (Carcharhinus perezi, Negraprion brevirostris, and Ginglymostoma cirratum) were studied using passive acoustic telemetry to assess movement patterns and use of microhabitats at Buck Island Reef National Monument (BIRNM), St Croix, United States Virgin Islands from 2013-2016. Carcharhinus perezi spent a majority of their time on the south side of BIRNM, while G. cirratum and N. brevirostris spent the majority of their time on the south side during the day and moved to the north side of BIRNM during the night. All three species preferred a mix of microhabitats consisting of sand, aggregated patch reefs and sand channels with scattered coral and rocks. Further studies are needed to fully assess the potential of labeling BIRNM as a nursery ground for these species.