Aquaculture  - Biotechnology topics

Wild salmon get their distinctive pink colour from natural pigments called astaxanthin and canthaxanthin. These pigments are found in planktonic algae and cyanobacteria (aquatic bacteria that, like plants, are able to manufacture their own food using the energy of sunlight [photosynthesis]). Algae and cyanobacteria are eaten by other organisms, such as krill (tiny shrimp-like plankton). When these are eaten by wild salmon, the pigment gets absorbed by their muscles, turning their flesh pink.

Algae, cyanobacteria and krill are not a normal part of the food used to feed farmed salmon. And, without the pigments derived from these organisms, the salmon’s flesh would be creamy coloured, rather than the pink colour preferred by consumers. This means that, prior to marketing, salmon feed needs to be supplemented with synthetic versions of astaxanthin and canthaxanthin pigments in order to turn their meat pink.

Synthetic carotenoid (i.e., coloured yellow, red or orange) pigments represent about 15-25% of the cost of production of commercial salmon feed. So, if a less expensive method could be found to produce the pink colouration required for salmon flesh, this would lower one of most significant costs associated with producing farmed salmon.

Researchers at Fisheries and Oceans Canada (DFO) are exploring the use of molecular technology to develop alternatives to synthetic astaxanthin and canthaxanthin. They are investigating three alternative methods:

• the production of plants that have been genetically modified to produce these pigments;
• the production of salmon that can produce the pigments themselves; and,
• the improvement of the ability of salmon to take up and deposit these pigments in their flesh, so lower quantities would be required in their feeds.

Few plants or animals have the ability to produce astaxanthin and canthaxanthin naturally. DFO researchers, therefore, have to first find and identify those aquatic organisms that can produce these pigments. Once these are identified, the researchers will search for the genes that make those organisms capable of producing the desired pigments. When those genes are identified, the researchers will then incorporate the genes into plants to see if this makes the plant capable of producing astaxanthin and canthaxanthin. Any plants that demonstrate this capability will be investigated further to see if they can be incorporated into a salmon feed that salmon will readily eat and digest.

Researchers will also examine the genetic makeup of the salmon to identify the genes responsible for deposition of pigment into their muscles. When this is accomplished, these genes will be studied to see if they can be used in selective breeding programs to develop strains of salmon with an enhanced pigmentation ability. This would lower the levels of synthetic pigment supplement needed in their feed.

This research should benefit Canada’s salmon aquaculture industry by:

• lowering salmonid feed production costs, thereby lowering overall production costs to salmon farmers; and,
• increasing opportunities for aquaculture feed companies to develop new products.