Photocaption: Cod at day 54: Artemia-fed control at the top, Gemma Micro-fed below
The upgraded Gemma Micro was trialled in several leading hatcheries in Spain, France and the USA during 2009 with impressive results. All hatcheries reported the diet is easy to use whether feeding by hand or by automated micro-feeders. It spreads readily on the water surface and sinks slowly. Fish larvae were quick to adapt to the feed, which Skretting recommends is co-fed with rotifers over the first few days after introduction using a simple meal feeding technique developed by Skretting. This moderates the speed of passage through small larvae to ensure they benefit fully from the nutrition. The patented formulation is based on pre-digested proteins and phospholipids with other ingredients such as a carefully selected blend of marine micro algae that give the feed a green colour. Eamonn O’Brien, Product Manager for Skretting Marine Hatchery Feeds, explains the reasoning. “Marine larvae in the wild eat a wide range of organisms including marine algae. Our aim is to mimic this natural diet. High quality algae are also vitally important in the live feed period and it is logical to formulate replacement or weaning diets with this in mind. The marine algae deliver a positive prebiotic effect that is good for larval health and efficient digestion, providing a significant benefit in larval rearing.” The Skretting feeds that follow Gemma Micro, the Gemma Wean series, also contain marine micro algae.
In the hatchery trials, Gemma Micro led to significant improvements in growth rates compared with conventional Artemia diets. For example, at a hatchery in Spain sea bream at day 65 averaged 246 g compared with 176 g for Artemia-fed controls. Survival rates were the same or better; in some instances the improvement was substantial — up to 30% higher. In one sea bass trial the survival in the Gemma Micro batch was twice that in the Artemia batch. O’Brien adds, “Overall, we saw greater consistency in production with the new formula Gemma Micro. Fry fed with Gemma Micro were more vigorous and moved readily into the next feeding phase, taking their growth momentum with them. Deformity rates were the same or better. Additionally, eliminating Artemia reduces the risk of introducing pathogenic bacteria and viruses to the rearing system and releases staff time for production of fish rather than live feed. The final benefits are the reliable quality of the dry feed and a shelf life of two years. Coupled with the improved performance, these factors reduced the overall cost of production in all trials.”
The quality of Artemia has become erratic in the recent past. Lower hatching rates and poor separation mean more work to provide an adequate supply of nauplii. In marine hatcheries Artemia can represent 50% of total feed costs as well as requiring extra time and energy. Additionally, there are concerns over sustainability and origin of Artemia as demand from fish and shrimp hatcheries increases with the growth of aquaculture. These challenges are prompting many marine hatcheries to investigate changes in their early feeding protocols with a viable alternative. Further growth in aquaculture is inevitable as fish farmers seek to meet the increasing demand for fish from the expanding world population. The new Skretting feed could be an answer that will enable aquaculture to meet that demand in the years to come.