BY JORGE BUENING, GENOA NFH
It is typical during the culture of fishes to make changes to rearing tanks and feed sizes as the fish grow. In the case of our cold-water culture, trout species are gradually given larger and larger tanks to occupy. Basically, larger fish require larger spaces. As trout grow they also progress through larger and larger feed pellets. A fish exerts more energy and effort eating many tiny pellets as opposed to a few larger pellets. The problem is…wasting energy can result in slower growth. This would not allow us to meet the management objectives that are set in place for our stocking locations. These principles also hold true for lake sturgeon culture, except to a much higher degree.
Lake sturgeon, a cool water species, are also given more space as they grow, just like the trout. However, this process is accelerated due to the niche that sturgeon occupies. It is a species that generally inhabits the bottom of the water column. No matter how much water is above them they have maximized the capabilities of a tank when the bottom of the tank is full. From a feed perspective they are very finicky compared to their cold-water counterparts. Currently, lake sturgeon require natural diets in order to be intensively cultured. Instead of transitioning from one size feed to the next, they transition onto a completely different diet.
When lake sturgeon first hatch they absorb their yolk sac for a few days and then begin actively searching out feed sources. Initially, lake sturgeon are planktivores and eat zooplankton. During this feeding stage we provide them with brine shrimp nauplii. As they continue to grow sturgeon begin to target larger invertebrates. We alter their feed regime and introduce ground bloodworms during this stage. Eventually, the sturgeon grow large enough to eat whole bloodworms and we are able to give our food processors and meat grinders a rest. Lastly, the sturgeon are transitioned onto krill, the same stuff that some whales eat. This protein rich crustacean allows the sturgeon to really grow and beef up before the fall stockings.
The science and art behind fish culture is always changing. At Genoa National Fish Hatchery we strive for efficient and quality culture practices that result in meeting all of our stocking and production requirements. We hope these standards will lead to the stocking of tens of thousands of lake sturgeon and trout in the coming year.