City slickers: Miami’s sharks

The overall aim of this project is to understand how coastal urbanisation effects the distribution, movements, trophic niche breadth as well as the physical and physiological health of coastal sharks in South Florida.

Animals living in urban landscapes are subject to increased anthropogenic threats. South-east Florida has been identified as a global hotspot for ‘coastal syndromes’, which are areas marked by synergistic human-stressors including habitat fragmentation, eutrophication, species loss and water run-off. Research along Florida’s shoreline has documented decreases in fish abundance and diversity in degraded habitats; however, such information is lacking for top predators, particularly sharks. This is of significant conservation concern given declines in many shark populations, and their ecological importance and vulnerability to exploitation. Florida’s coastline is inhabited by various shark developmental and life-history stages, which are distributed along and subjected to a wide gradient of coastal urbanisation; however, the ramifications of this urbanisation on shark fitness remain unknown. Accordingly, there is a need to better understand such dynamics and, moreover, how aspects of urbanisation can be managed to conserve natural marine resources while maintaining socioeconomic growth.

Coastal habitats are some of the most ecologically and socioeconomically important on the planet, and development and urban sprawl have long been cited as major anthropogenic threats to coastal ecosystems. Despite these human-induced changes, many of these ecosystems are today used by a variety of flora and fauna that were previously associated with pristine, undisturbed habitats. This suggests that the variety of coastal marine fauna which persists in close proximity to humans may have adapted to new stressors, food sources and predators. Thus the processes and patterns that shape species change and biodiversity around coastal cities need to be better understood.
To date research aimed to better understand and mitigate the effects of biodiversity loss have often overlooking altered urban ecosystems. Yet urban areas can serve as laboratories for studying the ecological and evolutionary selection processes that govern change, thus providing information vital to conservation efforts.
Despite drastic declines in certain US shark populations, the state of Florida represents a regional hotspot for shark abundance across various developmental and life history stages (neonates and juveniles, as well as adults), which are distributed along and subjected to a gradient of anthropogenic disturbance and urbanisation. Also represented in this species diversity is a spectrum of regional and international threatened statuses, as well as a range of ecological and functional specialisations, which can influence survival in light of anthropogenic risk. Adding further complexity to the management of sharks in Florida waters is our lack of knowledge about the impacts of urbanisation on the basic life history, reproduction and connectivity of coastal shark populations. The unique combination of high regional shark abundance and biodiversity in an urbanised environment presents an interesting opportunity to better understand how aspects of global change impact species survival, and ultimately, how anthropogenic stressors can be managed to conserve natural marine resources while maintaining socioeconomic growth.

• Determine shark distribution, habitat use and residency patterns across a gradient of habitats from highly altered/developed to relatively pristine. This will be accomplished using a combination of standardised drumline surveys and acoustic tagging in the study area.
• Evaluate the trophic niche breadth of sharks in relation to movements and habitat use in developed/degraded versus pristine habitats.
• Investigate the relationships among shark body condition and energy state in high altered/developed versus relatively pristine environments.
• Evaluate shark psychological stress (serotonin levels) across a gradient of habitats from highly altered/developed to relatively pristine.
• Examine bull shark use of highly developed and disturbed urban water systems, specifically the Miami River, Turkey Point nuclear power-plant cooling canals and the Bear Cut channel in Key Biscayne, Florida. This will be accomplished using acoustic telemetry.