For the past five years, Dr. Shawn Robinson, a scientist with Fisheries and Oceans Canada's (DFO) Biological Station in St. Andrews, New Brunswick, has been working with a team of colleagues from DFO and the University of New Brunswick (UNB) on integrating other species with Atlantic salmon culture in the Bay of Fundy. Their internationally acclaimed research has focused on growing various organisms from different levels in the food chain (i.e. kelp, a form of seaweed, and blue mussels) alongside Atlantic salmon sea cages. The theory is that the growing of multiple species will provide a more balanced ecosystem approach and a more economically efficient industry.
Dr. Robinson, who is co-leading the project with Dr. Thierry Chopin at UNB using funding provided by the Networks of Centres of Excellence AquaNet program, views the polyculture concept as the way of the future. According to Robinson, "Salmon naturally produce organic and inorganic waste as a result of their feeding and metabolic activities like all organisms. Releases from the salmon farm such as nitrogen, phosphorus, uneaten feed etc. are high-quality natural inputs for other organisms in the food chain. The kelp and mussels are natural consumers of the dissolved nutrients and fine organics and effectively recycle part of this excess production from the salmon that would otherwise be lost to the farmer and potentially impact the surrounding environment. We have found that growth rates and quality of these species are very high when grown alongside the salmon cages."
The kelp originates from Dr. Chopin's laboratory where he has been successful in fine-tuning "spawning" and grow-out methods from seed through to rope culture in the seawater for several species. Acadian Seaplants Ltd. is investigating the marketing of the seaweeds. The mussels used in the study are collected by the salmon industry itself as they clean their nets in the spring. What was once a nuisance species that had to be disposed of is now a valuable resource that can generate more income for the farmer. The mussels are put in socks and then hung on rafts in close proximity to the salmon cages. Three Heritage Salmon Ltd sites in the Bay of Fundy grew kelp and mussels alongside their cages with hopes of commercially harvesting the product in the future. Their successors, Cooke Aquaculture Inc. is also planning to incorporate this concept into their operation.
While the team is optimistic about their findings, there are still a number of management issues to consider. The first and foremost concern is consumer safety. In the Bay of Fundy and many other locations in the world, blue mussels filter and accumulate naturally-occurring micro-algae from the water. In the summer, some of these algae are responsible for temporarily rendering the shellfish unsafe for human consumption causing paralytic shellfish poisoning (PSP) or amnesic shellfish poisoning (ASP) in humans who eat the affected shellfish. As a result, the project is working closely with the Canadian Food Inspection Agency (CFIA) to test the mussels on a regular basis for PSP, ASP, bacteria and any chemicals to determine when mussels are safe to eat and to develop a rigorous, international standard system of monitoring should polyculture prove feasible.
Over the last several years, graduate students have conducted surveys with the general public to measure some socioeconomic factors associated with polyculture. Although many respondents were concerned with the number of aquaculture sites and their environmental "footprint", most thought that this approach was a significant improvement in the way we grow food. They also indicated they would be willing to pay more for sustainably-produced seafood.
Other environmental interactions are also being studied as DFO oceanographers are working to determine water current and oxygen use parameters. Salmon need oxygen to survive and concerns have been expressed about adding other oxygen-using species in close proximity to the fish. The results indicate that the risk of negative interactions is low.
While these studies continue, Robinson is optimistic. "Multi-species farming is not new. Land-based farmers rotate crops to benefit from nutrients released from various products and also grow certain plants along side others for this reason. It seems natural that we should do the same in the ocean as a way to make farming the sea more environmentally friendly and more economical. We are simply copying ecological systems that have evolved over millions of years. The key to industrial evolution is to make the transition attractive to the producer from a fiscal perspective. If we can demonstrate a better way to do business, then our marine production industries will evolve naturally to a more sustainable and benign phase."