Mortality and developmental deformities during the larval stage are bottlenecks in farmed cod production. And scientist believe this is primarily down to nutrition. In the wild the cod larvae feed on copepods however, farmed cod larvae depend on a diet of live zooplankton, such as rotifers due to their immature digestive system.
However, analyses have shown that rotifers contain low amounts of selenium and other minerals such as iodine, manganese, copper and zinc. The levels are far lower than those found in natural copepod-based diet.
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| Researcher Samuel James Penglase is studying enrichment of rotifers at NIFES as a part of his masters degree work at the University of Bergen. Photo: NIFES |
However, new research using selenium enriched rotifers is proving successful.
Investigations at the National Institute of Nutrition and Seafood Research (NIFES) has shown that cod larvae fed rotifers enriched with iodine and selenium have a higher survival rate than those larvae fed a control diet.
“This indicates that the control rotifers were deficient in either iodine or selenium or both,” said researcher Kristin Hamre in the Aquaculture Nutrition Research Programme at NIFES.
Selenium is a component of an enzyme that prevents cod from absorbing rancid fatty acids. Scientists believe deficiencies may affect growth, survival and the development of deformities.
"We do know, for example, that rancid feed does result in deformities,” added Ms Hamre.
Further Enrichment
In connection with using the selenium-enriched yeast, new routines will also be developed for the enriching of rotifers with other nutrients and trace elements.
“The rotifers will be given both algae and enrichment substrates in use in cod aquaculture facilities today, but they will also be given extra selenium,” explained Australian student-researcher Samuel James Penglase, He is doing his masters' at University of Bergen and NIFES.
The project is being managed collaboration with Alltech AS, who produces the selenium-rich yeast Sel-Plex. A further study is about to get underway and will examine if adding selenium-enriched yeast to rotifers can supply the cod with enough mineral to benefit growth and survival rates and reduce the incidence of deformity.
The yeast will be added at different levels and the benefits/outcomes observed.
For further Information visit www.NIFES