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Denmark feeding regime produces highest survival rate in European eel larviculture
July 28, 2022 By Ruby Gonzalez
A feeding regime developed in Denmark has been credited for producing the highest survival rate in European eel larviculture at 20 per cent at 20 days post-hatch.
The feeding regime involved pre-feeding starting at four day post-hatch and feeding starting at 10 days post-hatch. The control group’s feeding regime didn’t have a pre-feeding period. Animals were fed with diet using pasteurized thornback ray (Raja clavata) egg yolk, deskinned krill extract and a small portion of soybean peptides.
Although the early introduction of feeding reduced larval survival rate, no differences in survival rate between the feeding regime and control groups were posted at the end of the experiment.
With growth hormones and triglyceride lipase expressed at a higher level in prefeeding larvae compared to those in control, results indicated that prefeeding might be advantageous, in spite of observed mortality, Elisa Benini et al explained. They cited, however, the need for further research, timing of feed application.
Benini is a PhD student at the Technical University of Denmark. She and her team is behind the research article published on Aquaculture Reports, “Transition from endogenous to exogenous feeding in hatchery-cultured European eel larva.”
Through experiments, the study tested different feeds and feeding regimes for European eel larval culture and explored the effects of early feeding during the transition from endogenous to exogenous feeding stage. “In this regard, establishing a first feeding culture of European eel is at a pioneering state, where successful production of viable larvae and enhanced larval culture technology increasing early larval survival has only recently enabled feeding experiments,” they said.
Three diets and their potential benefits of early feeding during the transition from yolk-sac stage to feeding larvae were explored, including molecular analyses of genes involved in digestive functions and growth. All diets were prepared fresh daily.
“The transition from endogenous to exogenous feeding is critical during fish early life, where appropriate feed availability and timing of initiation of feeding influence survival,” they said.
During the endogenous feeding stage, the animal exclusively utilizes its yolk reserves. Reliance on external feeds starts at the exogenous feeding stage.
The establishment of feeding larval culture presents a chokepoint in the diversification and closed-cycle production in aquaculture, the authors noted.
While standardized larval culture procedures have been established for a range of aquaculture species, results have not been satisfying. There are cases of often low or variable survival rates and growth potential in many cases is not fully utilized.
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