The ghost sharks of western Norway
Of all sharks and their kin, chimaeras (also called ghost sharks) are the least studied and understood. Traditional surveys have recorded chimaeras at great depths, below 300 metres (985 feet), and they are considered deep-sea locals. However, Norwegian divers have seen chimaeras in fjords at a depth of just 30 metres (98 feet). Lotte will use acoustic telemetry to complete the first advanced tracking study of chimaeras. She wants to identify whether they exhibit resident or migratory behaviour, understand their social interactions and assess their population structure in order to improve understanding of chimaeras and help protect them and their key habitats.
Lotte Dahlmo
I am a marine biologist with a background in aquaculture (Bachelor’s) and fisheries ecology (Master’s) at the University of Bergen. My PhD project in marine biology focused on marine fish recruitment, in which I studied whether fish larvae, which have a relatively limited capacity to swim, exhibit specific movements in response to external stimuli. By conducting lab experiments, I showed that both cod and herring larvae exhibit behavioural response to light and temperature, and that this behaviour can depend on stomach fullness, meaning that whether a larva has recently eaten or not can impact its behaviour. Since my...
Unravelling the behaviour of the ghost shark in Norwegian fjords using acoustic tracking (Ghost Track)
Chimaeras are some of the most enigmatic species of elasmobranchs in the ocean and little is known about their behaviour or movements. Using a method for tracking aquatic animals, we observe the movement ecology of chimaeras in coastal fjords in western Norway for the first time.
As the details of elasmobranch biology continue to be filled in, chimaeras remain understudied and poorly understood, despite being vulnerable to bycatch and some targeted fisheries for their oil. Tracking studies can help substantially to understand their behaviour, movement and sociality and thus support better regulations for protecting these species in their native habitats.
Chimaeras form a special group of cartilaginous fish that are distinguished from sharks and rays by their unique shape: a big head with big eyes, pelvic fins that are large, and a tail that is long and thin. They have an oily liver that helps to maintain their position in the water column, but it is valuable and chimaeras are therefore increasingly caught by fishers. In Norway, chimaeras are also vulnerable due to recreational gill-net fishing or recreational fishing for cod and other fish species found in the fjords. Despite their broad distribution globally, very little is known about their behaviour and movement patterns. According to traditional surveys, chimaeras are often caught at depths of 300 metres (985 feet) and below, and are therefore considered deep-sea species. However, local divers have observed chimaeras in Norwegian fjords at depths of no more than 30 metres (98 feet). By using a form of tracking called acoustic telemetry, we aim to conduct the first advanced tracking study of chimaera species and thereby fill knowledge gaps about their behaviour and movement. We will investigate how time and space affect their behaviour and movement by inserting a small electronic transmitter into their abdominal cavity.
The Ghost Track project will greatly enhance our understanding of chimaeras and help protect them and identify key habitats that are important for them. It aims to:
- Develop a tagging methodology that will be available to other researchers.
- Study the habitat use, identify resident or migratory behaviour, understand social interactions and gather additional data on population structure from a small sample of chimaera fin.