Einar Eg Nielsen, Professor of Fish Genetics at DTU Aqua, has used modern genetic analyses to examine why the West Greenland cod disappeared.
Together with colleagues from DTU Aqua, Aarhus University, and the Greenland Institute of Natural Resources in Nuuk, Professor Nielsen used the DNA tool to study the disappearance of the fish which was Greenland’s main economic resource in the 1950s and 60s.
He said: “People have always discussed the cause, when large fish stocks disappeared. Was it due to environmental changes or overfishing? We now have a tool that has made it possible to ‘travel back in time’ and find out exactly what went wrong.”
It has been possible to find out which types of cod were caught because the Institute of Natural Resources has a large collection of several hundred thousand old ear stones from cod caught off the west coast over the years.
The ear stones are calcium carbonate structures from the cod’s head traditionally used for age determination, as they grow like rings in a tree.
As well as this the ear stones have microscopic traces of blood and mucus from the cod, this was used for DNA analyses to determine which stocks the fish belonged to.
"If you don’t examine which stocks are caught, you cannot explain why the fishery collapsed. So this is knowledge that simply wasn’t available at that time, because they didn’t have the same methods as we do today," Professor Nielsen added.
He continued: “Fishing in West Greenland first collapsed because of overfishing of the local Greenlandic stock, and as the environmental conditions changed at the same time, among other things resulting in lower temperatures, the area offering favourable living and reproduction conditions for the cod diminished.”
The genetic analyses highlighted to researchers that the cod caught off West Greenland actually originated from several different stocks.
With the new found information Professor Nielsen posed a theory on what should have been done in the past to stop the collapse of fisheries: “They should probably have concentrated the fishery in the southern part of West Greenland which had the largest population of Icelandic cod, or generally have caught far less cod.”
