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Unraveling population connectivity in the deep sea

DEECON is currently developing scientific tools from such diverse fields as molecular biology, trace element analysis, and oceanographic modeling, and integrating them into a concerted interdisciplinary approach to unravel population structure and connectivity in selected commercially important deep sea fishes.

by Halvor Knutsen and Per Erik Jorde

Coryphaenoides ruperstris
The Roundnose grenadier, Coryphaenoides ruperstris.
 

As most traditional coastal fish resources are heavily over-exploited, commercial harvesting have shifted towards less-known, deep-sea living organisms in many parts of the world. Most of these new fisheries are now proving to be unsustainable. A key to our ability to manage these fisheries and protect ecosystems is an understanding of how they are structured into geographically independent populations. 

In a recent workshop in Horta, Azores, partners from all participating research groups (from DOP in Portugal, University College Dublin Ireland, Marlab in United Kingdom, and Institute of Marine Research and CEES/University of Oslo, both in Norway) met and exchanged notes and preliminary findings.

Otolith with laser ablation marks
Otolith with laser ablation marks

One of the target species in DEECON  is the Roundnose grenadier (Coryphaenoides rupestris), a deep-sea fish inhabiting the continental slopes around the North Atlantic.  The population structure of the species is characterized using molecular genetic tools, including microsatellite DNA polymorphisms and mitochondrial DNA sequence data. The results demonstrate that the species is not panmictic throughout its range, but instead consists of partly isolated populations that differ in genetic composition. Particularly strong patterns of differentiation appear in isolated populations in e.g. deep Norwegian fjords.

A novel approach to supplement molecular genetic analyzes is characterization of trace elements in bony structures such as the otolith. By means of laser ablation, minute quantities of material are removed from well-defined positions along the otolith, and subject to chemical analyzes by plasma mass spectrometry (LA¬ICP/MS). Measured levels of elements, including Lithium, Zinc, Magnesium, Strontium, Copper, and Barium, provide a chemical signature of the water masses experienced by the growing individual, and will be used to test hypotheses on population structure and connectivity at various life stages.

Origins of virtual "larvae" ending up along East Greenland
Origins of virtual "larvae" ending up along East Greenland

Oceanographic modeling is used to trace potential dispersal routes for the young, pelagic life stages. By populating the habitable parts of the North Atlantic with a large number of virtual particles, computer models of ocean currents are used to track particles, now interpreted as pelagic larvae, as they are passively transported away from their origin to potentially settle in a new habitat. The modeled pattern of larval dispersal is used to draw inference on potential connectivity and gene flow among populations.


Based on a well-balanced mix of proven technology and new approaches DEECON is presently acquiring new fundamental biological knowledge that will be put forward for developing scientifically sound management plans for one of the world's most valuable ecosystems.

Funding:
ESF/EUROCORES – “EURODEEP”
Norges Forskningsråd - NORWAY
Fundação para a Ciência e a Tecnologia – PORTUGAL
Irish Research Council for Science, Engineering and Technology – IRELAND
Mar-Eco

 

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