A team of St. John's scientists is using DNA technology to trace the origins of the codfish, with evidence pointing to a single fish that swam off Newfoundland tens of thousands of years ago.

Geneticist Steve Carr says researching cod DNA is like assembling a massive jigsaw puzzle.
(CBC)

"The same way that for humans we're able to construct a family tree of individual human beings where every individual that we've looked at has a unique DNA sequence, we can do the exact same thing for the codfish," said Steve Carr, a Memorial University geneticist.

Carr is interested in what is called a "codmother" — a single fish from which all of the world's cod originated. His theory is that that one fish dates back about 162,000 years ago, somewhere off Newfoundland.

"Now there were other cod living at that same time. It's not to say that there was only one fish at that time, but that all [subsequent] cod share that individual as an ancestor," he said.

Working in a biology lab in St. John's, Carr's team is using a technology called phyleogeographic genomics for its research, the latest of which was published this week in the journal Comparative Biochemistry and Physiology.

A tiny computer chip is loaded with the DNA of a cod, and the chip is then rapidly processed, producing a sequence that resembles an elongated Scrabble board.

"Imagine looking at a jigsaw puzzle of 16,000 pieces. We are putting that together maybe 500 pieces at a time," Carr, who has been researching cod biology for about 20 years, told CBC News.

The genomic project seeks to find origins of the codfish in the Atlantic Ocean, off the coast of Newfoundland.
(CBC)

"The new method that we're using determines the entire genome sequence in one experiment that takes only a few minutes."

Carr's research may have practical uses that extend far beyond the curiosity of knowing the cod's origins.

Gary Stenson, a research scientist in St. John's with the Department of Fisheries and Oceans, said the research is critical to understanding different populations of cod, which could help fisheries managers deal with cod stocks that have been threatened for a full generation.

"Once you get the population structure sorted out, it's critical to allow you to do any of your management," Stenson said.

Carr himself is cautious about anecdotal reports of healthy supplies of cod in some inshore areas.

"When we see cod in a particular area coming back, we can't just go there and start our fishing practices again," he said.

"We have to let numbers in that area recover, because recovery of local numbers is key to recovery throughout the area."

The federal government imposed a moratorium on northern cod, the largest population of cod in the Atlantic, in 1992. Limited commercial fishing has been allowed again in recent years, but at a tiny fraction of what was caught in the years leading up to the cod collapse.

The technologies that Carr is using have been applied to human research. Carr is on the cusp of using it with several non-human species, including salmon, caribou, wolffish and harp seals, and to study how these species interact with nature.