Seeking ghost shark secrets

  • Sharks
Years funded
  • 2024
  • Active
Project types
  • Conservation
  • Education
  • Research

Karly is diving into the depths of the ocean – and time – to uncover the mysterious lives of Pacific spotted ratfish. Chimaeras (or ghost sharks) are ancient kin of modern sharks and they are found in abundance in the Pacific Northwest. Despite their ubiquity (and antiquity), we know little about them: where do they breed? How do they develop? Karly is harnessing technology, from ROVs to 360° cameras, to understand how ratfish reproduce and start their lives. Partnering with the University of Washington, Florida Museum of Natural History, Seattle Aquarium, local fishermen and conservation groups, she will deliver powerful education about these ancient shark cousins.

Seeking ghost shark secrets

Karly Cohen

Project leader
About the project leader

I am currently a postdoctoral fellow at the University of Florida’s Department of Biology. My research dives into the world of hard skeletal tissues – their evolution, how they develop and the mechanics behind them. I received my PhD in biology in 2022 from the University of Washington, having researched the development, morphology and mechanisms of feeding in fish. I developed successful research and mentorship programmes at both the Seattle-based university and its marine field station, Friday Harbor Laboratories, by exploiting the unique advantages of each location. A microcosm of life and research, Friday Harbor Labs...

Project details

Discovery and development of chimaera (Hydrolagus colliei) nursery grounds in the Pacific Northwest

Key objective

To discover the breeding and nursery sites of spotted ratfish by means of trawling and remotely operated vehicles and, by documenting the species’ embryonic development, to investigate the intricate mechanisms governing early tooth-plate development. This endeavour holds promise for unveiling new insights into the evolutionary trajectory of vertebrate teeth.

Why is this important

We know shockingly little about a species that boasts some of the greatest biomass in the Pacific Northwest. The spotted ratfish is an elusive and deep-sea cousin of modern sharks, and we have no clear understanding of where it reproduces or how it develops. Our research will begin to establish nursery sites, understand potential disturbance and use data from remotely operated vehicles to build interactive exhibits that will help to engage future generations.


Chimaeras, or ghost sharks, are ancient cousins of sharks and hold secrets from the depths of time. These enigmatic fish are from some of the oldest cartilaginous lineages, yet their natural history remains largely unknown. Like some other shark species, chimaeras lay eggs, but their elusive behaviour and the depth at which they live have made it difficult to find and document their breeding and nursery sites. Discovering these hidden spots is crucial for understanding their population and reproductive history.

Our team employs cutting-edge techniques, like trawls, remotely operated vehicles (or underwater drones) and 360-degree cameras to gather data about chimaera habitats. The drones meticulously survey the ocean floor, revealing habitat types, egg density and other population dynamics without disrupting the delicate ecosystem. Partnering with the University of Washington, Florida Museum of Natural History, Seattle Aquarium, local fishermen and conservation groups, we aim to uncover ratfish reproduction strategies and early life stages. Through this project, we connect the dots, improving conservation, awareness and education. By unravelling the mysteries of these ancient fish, we’re painting a vivid picture of the oceans’ past and inspiring people worldwide.

We are also interested in how ratfish develop, especially with regard to their teeth. All vertebrates build their teeth with the same set of genes and cells, a genetic toolbox that appears to be millions of years old. Ratfish stray from typical dentitions by having fused tooth plates rather than individual teeth. Unlike other sharks, they bear no skin denticles, except for the male, which has a tenaculum on top of his head. By studying the early development of ratfish, we can better understand these early mechanisms of tooth generation and where dental diversity arises.

Aims & objectives
  • To discover hidden nursery sites of the spotted ratfish with the aid of underwater drones. The video footage from the drones will also be the basis for virtual reality exhibits on sharks, called ‘Swimming with ghost sharks’, that will allow viewers to experience what life is like for some of the most abundant fish in Washington.
  • To raise embryonic ratfish and document their growth, particularly the development of their unique dentition, to enhance knowledge of early vertebrate evolution.