In a recent study Polish researchers have determined what they believe is the optimal feeding level for burbot larvae fed freshly hatched brine shrimp during three different rearing larval stages.
The 36 day project by researchers at the University of Warmia and Mazury, Aleja Warszawska in Olsztyn, Poland looked at three phases of larvae development from the first which studied larvae from 22-34 days post-hatch (DPH), to the second 34-46 DPH, and final phase at 46-58 DPH.
"In our lab we were working on burbot for over 10 years developing our hatchery protocols, Daniel Zarski, one of the authors of the research report told Hatchery International.
The research was done in Poland, but included Zarski and others from other Eastern European research universities.
"The nutritional requirements were strictly dependent on the allometric growth pattern of this species and behavioral changes of this fish at the transition from pelagic to bottom-like 'life style,'" he said. "However, this should be specifically studied, as we have not made the behavioral experiments, although we have our 'personal' observations," as well.
While feeding larvae by the common technique has a positive effect on their growth rate, knowledge of the minimal ration (which would guarantee larvae in good overall condition [e.g., high specific growth rate, condition factor, and survival]) is important to the cost-effectiveness of the production process since feeding the larvae with live food generates higher costs, according to the report.
Results obtained in the study provide, for the first time, information on how to determine the smallest optimum feeding rations of freshly hatched Artemia nauplii (while maintaining a high survival and growth rate) which should be given to burbot at different stages of their development (i.e., between 22 and 58 DPH).
The study's findings indicate the specific dynamics of live food requirements of burbot at different ages, until the fish reached a size that allowed effective weaning to commercial diets.
The main factors which affect the survival rate of the early life stages of burbot include temperature, photo-period, and feeding regimes as well as the amount and type of food. A high survival rate of larvae was always considered to be an important indicator of the effectiveness of rearing procedures.
The survival rate of burbot larvae in the present study was very high (always over 90%) in each group and in each rearing period. This is the highest survival rate of burbot larvae observed during rearing to about 60 DPH. While it may be suggested that feeding burbot with the ration of 2% of biomass/d was sufficient to maintain a high survival rate, it was not sufficient to achieve a high growth rate.
"This study gives a clear protocol how much Artemia nauplii should be given to burbot larvae at different size. For this purpose the hatchery manager must only know the number of fish in the tank, determine the average wet body weight of fish and calculate how many Artemia nauplii should he give (according to the known dry weight of a single nauplii – which is accessible in literature)," he said.
In summary – the data provided clear instructions on how to calculate the amount of food to be given to fish, he explained. "And this presumably applies to other live food types (if dry weight is known and fish are able to ingest it easily), however, it should be verified under the lab conditions first."
— Erich Luening
For additional information get in touch with Daniel Zarski at: firstname.lastname@example.org