News & Views
Low water level, high performance for elver eel in vertical aquaculture system
By Ruby Gonzalez
Water level that is just enough to cover elver eel A. bicolor’s bicolor body (1.5 cm) in a vertical aquaculture system produced good growth performance indicators, said researchers in Indonesia.
“Elver eels A. bicolor could be reared in a container arranged vertically with a recirculation system and, in most cases, give the same responses to different water levels,” Eko Harianto et al. cited in “The effect of water level in vertical aquaculture systems on production performance, biochemistry, hematology, and histology of Anguilla bicolor bicolor,” published in Scientific Reports. The authors are from IPB University in Bogor.
“The water level of 1.5 cm provides advantage in several ways, namely the least in water use and gives blood biochemistry values that are the closest to normal condition, also the best concentration of temperature and dissolved oxygen.”
They likewise cited the level’s water usage efficiency.
Water levels of 1.5 cm, 2.25 cm, 3.0 cm and 3.75 cm were used in the experiments. Production performance based on a 60-day rearing period showed the different water level treatments had no significant effect on the parameters of survival rate, weight, specific growth rate, average growth rate, absolute growth rate of biomass, feed conversion ratio, and oxygen consumption rate. Survival rate was 100 per cent across all treatments.
In general, the study shows better results than the previous studies with the use of water volume of culture media, individual growth rate, and biomass of the eel A. bicolor bicolor stadia elver reared for 70 days at a water volume of 0.4 cubic metres.
Based on weight coefficient diversity, weight uniformity rate was also high. Weight coefficient diversity illustrates the level of weight diversity at the end of the rearing period. The lower the weight coefficient diversity values, the higher the weight uniformity rate is. Weight coefficient diversity values in this study was under 20 per cent.
Eel’s migratory movement patterns has made it adaptable to various depths of water. In a laboratory-scale, eel is bred and reared in regular aquarium with water depth of 20 to 35 cm. It is commonly between 50 and 200 cm deep in production scale-pond.