FORT PIERCE, Florida – Algae, zooplankton and other microscopic organisms are such a vital component of commercial fish hatcheries as a high protein food source that aquaculturists are always looking for ways to optimize their culture for higher fish nutrition and improved growth performance.
One aquaculturist in south Florida received a Southern Sustainable Agriculture Research and Education (SSARE) Producer Grant to study the efficacy of culturing live spirulina to provide a cost effective means of improving microalgae nutrition in bait fish.
Nicole Kirchhoff, founder of Live Advantage Bait in Fort Pierce, FL, said that spirulina (a blue-green algae fed as a source of protein and vitamins in fish husbandry) is most commonly used in powder form, but has not been extensively fed live.
“Most likely because spirulina is not a commonly live cultured species in the industry, so many aquaculturists are not familiar with its husbandry conditions,” said Kirchhoff. “But we experimented with live spirulina and found that compared to other microalgae species we culture (like Nannochloropsis), spirulina can be cultured at extremely high densities and at ambient temperatures of South Florida, meaning no additional temperature control is required.”
Kirchhoff also observed that live spirulina fed to rotifers (zooplankton popular as feed for larval fish) increase zooplankton density compared to the standard practice of using algae paste products.
“These preliminary observations demonstrate that live spirulina culture may enhance the performance of marine aquaculture hatcheries,” said Kirchhoff. “We are potentially creating a higher nutritionally valued product feeding it to the plankton and when it’s gut load fed to larval fish and clams. Larval fish and clams really don’t like to eat dead stuff.”
In the Southern SARE Producer Grant project, Kirchhoff is studying the performance of live spirulina, cultured in 4 foot high suntubes during spring, summer, fall and winter, and then presented as a live feed for hard clams and larval fish, and fed to rotifers as a live feed for pinfish. The production performance of feeding live spirulina will be measured against the standard commercial feeding methods.
Kirchhoff hopes that the results will demonstrate improved fish growth performance to maximize margins, and help farmers make daily decisions on feeding rates. “The goal is to produce more fish using live microalgae. If the live spirulina can increase the growth rate of fish, that means more cycles of fish per year per tank, and farmers make more money,” she said.
In addition, Kirchhoff is studying diatom culture optimization as an aquaculture live feed. Diatoms are unicellular algae that serve as a food source for many fresh water and marine animals. They are the only organisms with cell walls composed of silica.
“Literature demonstrates that live spirulina must be matched with a high fat microalgae species, such as a diatom, to provide optimal nutrition to marine fish and shellfish larvae,” said Kirchhoff. “Diatoms require an additional fertilization of silica, since diatoms have silica shells. Nutritional content of diatoms can vary with growth phase and silica availability; microalgae are most nutritious during the exponential growth phase. So we are looking for a way to balance that through batch culture.”
Batch culture of algae starts with inoculating a culture in the suntube with a small amount of algae and nutrients to initiate rapid growth of the culture, and then harvest the entire batch when the growth curve is maximized, said Kirchhoff. The idea is to calculate the ideal amount of fertilization and silica to use initially, and then determine on what day the culture would be the most ideal to harvest at its optimum nutritional level.
Kirchhoff is using Thalassiosira weissflogii, a large diatom commonly fed to shrimp and shellfish larvae in the experiment. Based on the results, Kirchhoff plans to develop a specific operating procedure that other aquaculturists can follow.
--Live Advantage Bait, LLC is a wholesaler of warmwater marine fish, fingerlings and eggs for baitfish and foodfish grow-out, research, and restoration. Live Advantage Bait was founded in 2013, and cultures such species as pinfish, Florida pompano, red drum, and Atlantic croaker. Live Advantage Bait is partnering with Great Florida Shellfish Company on some aspects of the project to reach shellfish farmers interested in live microalgae. --