Publication Date

2018-08-09

Availability

Open access

Embargo Period

2018-08-09

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Marine Ecosystems and Society (Marine)

Date of Defense

2018-05-07

First Committee Member

Neil Hammerschlag

Second Committee Member

Austin J. Gallagher

Third Committee Member

Jill L. Richardson

Fourth Committee Member

Andy J. Danylchuk

Abstract

The effects of urbanization and anthropogenic stressors have the ability to dramatically alter ecosystem function and habitats. Given the rates of population growth along the coast, urban centers continue to grow, which increase pressures on wildlife. Understanding the effects of urbanization and anthropogenic influences on apex carnivores is important considering the ecosystem services they provide. While published research pertaining to the movements of terrestrial urban carnivores is limited, more so are the effects of urbanization on the spatial ecology of marine predators. Understanding movement patterns of marine carnivores in response to urban-induced stressors is important when delineating zones of ecological importance often overlooked by conservation policy initiatives. Additionally, learning where urban carnivores move aids the management and mitigation of human-wildlife interactions. Here, I evaluated activity and habitat use metrics of three co-occurring species of coastal sharks in the subtropical Western Atlantic, along an urbanized gradient in Miami: great hammerhead (Sphyrna mokarran), bull (Carcharhinus leucas), and nurse (Ginglymostoma cirratum). This research was partitioned into three integrated steps. First, a review was performed on published research detailing carnivore movement ecology in urban settings across terrestrial and marine systems. Secondly, the results of this review were used to identify knowledge gaps in urban carnivore spatial ecology and to subsequently define an urbanized aquatic ecosystem as it related to my study species, large coastal sharks. Lastly, empirical analysis of passive acoustic biotelemetry was used to track the movements of 30 sharks, analyzing for metrics of activity and habitat use (number of detections, site fidelity, activity space) in relation to areas of urban influence. Results from multi-dimensional analysis revealed urban influence on marine waters is a mosaic within Biscayne Bay, and not simply a byproduct of linear distance to city center. Passive acoustic biotelemetry showed habitat preferences and increased activity to the most urbanized regions for all three study species within the defined urban gradient of Biscayne Bay. Trends indicated average detections per hour was highest during diurnal periods across all sharks. While analysis of activity spaces was non-significant, trends displayed shark movements to be unaffected by diel period, with slight increases in activity space area during nocturnal periods, when human activity is minimal. Activity and habitat preference results contrast the general findings within terrestrial urban carnivore research literature. Trends from activity space analysis are consistent with trends in terrestrial urban carnivore literature but should be considered with caution due to low sample size and non-significant relationships. Results have implications to the management of predatory species within urban ecosystems and can aid future scenarios of coastal population growth and urban planning, especially so for endangered species. Furthermore, results provide a better understanding of where sharks are in the urban-marine matrix, and what habitat characteristics are important for their existence. Given the important roles large bodied predators play in ecosystems, continuing research on how these species respond to urbanization, and how urban systems can be designed to better support apex predators is crucial.

Keywords

Habitat use; Urban; Shark movement; Acoustic telemetry; Residency; Urban gradient

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