Spirulina: The super food for… fish?


            Spirulina is and has been a popular topic among health food fanatics in recent trends, and rightly so. This microalgae is high in protein, lipids and carbohydrates, as well as vitamins, minerals, and antioxidants. It has been used as a human food supplement as well as a supplement in agriculture livestock. So, how about fish?

            Due to the increasing human population, wild fish stocks are being fished to capacity. The aquaculture industry has stepped in to fill the gap by providing an additional source of fish that is sustainable and reliable. As this industry grows, practices need to change in order for it to remain sustainable. Currently fishmeal and fish oil are heavily relied on as the main source of protein and nutrition in formulated fish food. This is a problem because fishmeal and fish oil come from the processing of wild pelagic fish such as anchovies and herring. If we continue to extract wild fish from the ocean for the purpose of feeding farmed fish, we will be taking away an essential food source for the larger carnivorous fish that sustain our wild fisheries. The use of an alternative protein source in formulated commercial fish feed is therefore required in order to keep the aquaculture industry sustainable.

            Here at Dalhousie’s Agricultural Campus, sustainability, global food security, and economic growth are important to the staff and students who attend this university. Therefore, the use of Spirulina as a partial replacement to fishmeal in diets for Arctic charr has become my main focus in the last year of my undergraduate degree. With the help of my supervisors, Audrie-Jo McConkey and Dr. Jim Duston, I performed a 3-month feeding trial using 120 Arctic charr and 3 different diets. The purpose of my study was to see if Spirulina could be used to partially replace fishmeal in diets for Arctic charr.

            During the feeding trial measurements of the fish were taken every 3 weeks, such as weight and length, as well as a calculated food conversion ratio (FCR). A food conversion ratio tells us how well the fish are converting the food into growth. A low food conversion ratio is essential to the profitability of a farm, as fish food tends to be one of the highest costs associated with many aquaculture facilities. The diets used in this trial consisted of a control diet, which contained no Spirulina, and was used to compare the results from the other diets. The other two diets consisted of 25% replacement of fishmeal with Spirulina, and 50% replacement of fishmeal with Spirulina.

            The results of the feeding trial found that the diet containing 25% replacement of fishmeal with spirulina had no negative effects on growth or FCR; while the diet containing 50% replacement of fishmeal with spirulina significantly suppressed growth, and increased the FCR. This means that spirulina can serve as a partial replacement to fishmeal in diets for Artic charr, up to 25%. This is one small, yet significant step forward in keeping aquaculture a sustainable industry.