The impact of fisheries on deep-sea food webs
New Zealand’s Chatham Rise is a global deep-sea shark hotspot. As fisheries and mining move deeper in search of catches and resources, sharks and rays below 200 metres (656 feet) are increasingly at risk of overexploitation. The problem is, we know very little about the lives of deep-sea sharks, and even less about how the entire system works. Deep-sea sharks probably play a key role in maintaining stable ecosystems, so what will happen as they respond to change and their numbers dwindle? Teah is detailing 30 deep-sea chondrichthyans on Chatham Rise, including the threatened school shark, leafscale gulper shark and spiny dogfish, to unravel how species are responding to intense fishing pressure.
Teah Burke
I grew up in Ontario, Canada, never far from the freshwater expanse of the Great Lakes. From an early age I always loved spending time outside, and my curiosity about the natural world was encouraged by my parents. It wasn’t until my undergraduate studies at the University of Windsor that I discovered my passion for saltier water (the ocean) while volunteering in a lab dedicated to understanding the movement and trophic ecology of fish from the poles to the tropics. While doing my Master’s degree I worked with species from both of those spectrums. I fished for...
The Impact of Fisheries on Deep-Sea Shark Trophodynamics
The primary objective of this project is to understand the ecological role of deep-sea sharks by determining how fishing pressure is altering the trophic structure of the deep-sea ecosystem over an extensively fished region, in this case Chatham Rise, New Zealand.
Information about the ecological role of deep-sea sharks is very limited. Deep-sea community structures may shift in the wake of increasing human-induced pressures and there is an urgent need to determine how species will respond. This project will leverage both historical and contemporary data collected from research trawl surveys to provide a valuable comparison for a highly exploited environment and establish a blueprint against which commercial fishing and human-induced impacts can be monitored into the future.
The deep sea (below 200 metres; 656 feet) is one of the least understood ecosystems on the planet, yet it is facing increasing threats from humans. As a result of declining coastal fisheries and increased interest in extractive activities (such as mining), there has been a growing global demand for deep-sea resources. Deep-sea sharks are targeted for their meat and liver, in addition to being caught as bycatch in fisheries. Among marine vertebrates they are some of the most vulnerable to overexploitation, due to their slow growth, long lifespan and low reproductive output. There are insufficient data about many deep-sea sharks, and understanding of the ecological consequences should they be exploited is limited. On Chatham Rise, New Zealand – a global hotspot for deep-sea sharks – they are among the most frequent bycatch in the commercial fishing industry. As high-order predators, these sharks are likely to play an important role in maintaining ecosystem stability in this region, but we know very little about their biology and their role in deep-sea food webs, or how they are responding to increasing fishing pressure and environmental changes. By using opportunistically collected samples of deep-sea sharks from research trawl voyages that focus on commercially important species in New Zealand, we can fill gaps in knowledge about the sharks’ diet and resource use and compare these results to data collected over the past two decades. This work will be used to monitor how species are responding to increasing anthropogenic threats in the region. Understanding the ecological role of deep-sea sharks will increase our knowledge of which species are most resilient – and which are most susceptible – to changes in the deep-sea ecosystem. This can guide conservation and management plans to ensure that species persist and recover and to promote overall ecosystem stability.
This project aims to better understand the role played by deep-sea sharks in their ecosystem and how human pressures have been impacting them. This will be achieved by:
- Generating a contemporary trophic and ecological dataset of up to 30 deep-sea chondrichthyans on Chatham Rise, including three threatened species: the school shark, leafscale gulper shark and spiny dogfish.
- Comparing contemporary results with trophic data obtained from past research trawls.
- Identifying how species are responding to intensive fishing pressure and which are most resilient and most susceptible to changes in the deep-sea ecosystem.