PhD defence about stock structure of capelin in Greenland

The small fish species capelin (Mallotus villosus) is one of the most abundant fish in the Arctic and an important prey to many fish, birds and mammals. 

At present, inshore capelin in Greenland, unlike many capelin stocks in the North Atlantic, are not fished commercially due to a gap in the knowledge about their stock structure and spatial dynamics. It has long been a question whether the inshore capelin belong to one coherent stock or are divided into multiple, separated populations. The extent of their migrations is also unknown.

During his PhD study, Peter Fink-Jensen, DTU Aqua, has examined the stock structure and migration behavior of inshore capelin in Greenland, using otolith (earstone) microchemistry to trace the spatiotemporal dynamics of capelin’s life history. Otoliths grow continuously throughout a fish’s life. Some elements are incorporated into the otoliths in relation to their concentrations in the surrounding water, and otoliths may therefore serve as chronological logs of environmental exposure.

For this study, otoliths of 619 capelin, caught at 19 locations along Greenland’s east and west coast, were examined by chemical analysis of 14 different elements. In many cases, fish caught at different localities showed contrasting element concentrations throughout their otolith chronology, indicating that they had been exposed to different environments and therefore had remained separated.

On this background, Peter Fink-Jensen concludes that many isolated populations of capelin exist along Greenland’s coastline, and he proposes that the inshore capelin may spend their entire life in one area, e.g., one fjord system. These results, he argues, have profound implications for fishery management of the stock and in order to avoid depletion of individual fjord populations, the stock should be managed at high spatial resolution, e.g., on a fjord-to-fjord basis.

About the PhD defence

Peter Fink-Jensen will defend his PhD thesis "Stock structure and connectivity of capelin (Mallotus villosus) in Greenland – Otolith microchemistry used to track past whereabouts of a small, pelagic fish” on Friday 24 September 2021 at 2:00 pm (CEST) via Zoom (find link below) and at DTU, Anker Engelunds Vej 101, 2800 Kgs. Lyngby, building 303A, auditorium 41.

Supervisors

• Principal Supervisor: Senior Researcher Karin Hüssy, DTU Aqua
• Co-supervisor: Senior Researcher Teunis Jansen, DTU Aqua and Greenland Institute of Natural Resources

Examiners

• Senior Researcher Martin Lindegren, DTU Aqua
• Assistant Professor John A. Mohan, University of New England, USA
• Researcher Tomas Naeraa, Lund University, Sweden

Chairperson at defence

• Head of Section, Senior Researcher Karen Edelvang, DTU Aqua

Learn more

A popular science summary of the thesis can be downloaded here

A copy of the thesis is available by e-mail on request. Please contact Karin Stubgaard, stub@aqua.dtu.dk.