Research Collaboration Benefiting Aquaculture Sector - National Research Council Canada

Aquaculture represents a significant industry in Canada, accounting for $586 million in sales for in 2003. Farmed salmon alone accounts for over 80 per cent of these sales. A joint Government of Canada and private sector collaboration is providing important research that will help expand this industry into other species such as Atlantic Halibut.

Halibut are valued for their size and quality. Despite these favourable characteristics, efforts to selectively breed for the best fish possible, a widely-used technique with livestock, have been hampered by the fact that these fish live a very long life and, for example, take 5-6 years to reach sexual maturity. In comparison, Atlantic salmon take two years to reach sexual maturity.

Genetic mapping, first developed during the rush to sequence the human genome, is now being used to quickly identify useful and desirable traits in this fish, such as rapid growth and disease resistance. The hope is, once these have been identified, industry can begin growing stock with these traits. So far, Canada is among the early adopters of this technique, in addition to countries such as Ireland, Norway and Scotland.

The project was initiated when researchers from Fisheries and Oceans Canada (DFO) in St. Andrews, New Brunswick, raised concern that many of the immature halibut being held for use as future broodstock could be related to one another, a fact later confirmed through genetic testing. "Debbie Martin-Robichaud, a DFO researcher, raised this possibility, which was a good thing, because if you were to go ahead and use broodstock that were related, you would quickly end up with inbreeding and many other problems," notes Dr. Michael Reith of the Halifax-based NRC Institute for Marine Biosciences (NRC-IMB).

Collaboration and Partnership

Project participants include NRC-IMB, DFO and Scotian Halibut Ltd. The project has received funding from the DFO Canadian Biotechnology Strategy, and Aquaculture Collaborative Research and Development Program (ACRDP) programs plus, more recently, through a Genome Canada/Genome Spain project called Pleurogene. In addition to initiating the project and providing funding, DFO has developed halibut spawning and culture techniques. Scotian Halibut has provided important information about the types of traits that are commercially significant, made crosses of fish identified with desirable traits and is helping raise the offspring of these crosses. NRC-IMB has provided specialized facilities and expertise required to develop genetic mapping and analysis techniques.

Work has focused on improving the understanding of exactly what genetic information is handed down between different generations of fish, in other words, what are the genetic linkages between fish. This is no small task considering that, like humans, nearly 100 per cent of the DNA in different fish is identical. But, pinpointing the variations is critical to determining the parentage of different fish as well as identifying useful traits.

During a process known as meiosis, chromosomes from the two parents pair up and exchange parts of their DNA, in the end creating a new chromosome which has inherited certain pieces of genetic material from each. In this case, not all information from the two original chromosomes is shared, rather, it's more a question of "a bit of this and a bit of that". The process is more formally known as recombination.

According to Reith, researchers are now interested in determining the rate of recombination between genetic markers, data that will yield information about the location of these variations. This type of information is extremely important because specific traits are often associated with genetic variations. And, to be able to select for these traits, you need a map to tell you where they are. "A genetic linkage map lets you organize DNA sequences belonging to different chromosomes and allows you to order them in a logical fashion, which helps greatly with analysis," Reith notes.

Consider a map at a scale of 1:100,000 scale. In this case, one centimeter equals 1 kilometre, making it very difficult to pinpoint features with any accuracy. But, with a map at a scale of 1:10,000, where one centimeter equals 100 meters, specific features are much more easily identified. In essence, the team wants a more detailed map to be able to identify with certainty genetic markers or genes associated with specific desired traits.

Reith also points out that the team is trying to identify different types of markers which will flag different types of information and different landmarks. Think of the map metaphor again. When you are getting down to a more precise neighbourhood level, features on the map include houses, but also different types of properties, such as parks, schools and retail and office space. A detailed map would contain all of this kind of information, so, too, does a genetic map, only instead of houses, and parks, the markers identify different categories of genetic variability.

Already the team has identified 200 unique genetic markers which pinpoint specific variations. The goal for the next phase of the project is to reach 1000 markers which will provide an infinitely more detailed picture. "This research has significant implications for the halibut aquaculture industry. By identifying these markers we hope that we can greatly accelerate the selection of a new broodstock and that their offspring will outperform the offspring of the original broodstock," Reith notes.