The Effect of Different Surface-Cleaning Devices on the Success of Swim Bladder Inflation in Zander Larvae

The failure of initial swim bladder inflation (SBI) is one of the main obstacles to successful results in Zander (also known as Pikeperch) Sander lucioperca larviculture because the larvae are unable to penetrate the oil layer on the water surface to gulp air. There are numerous technical solutions for cleaning the water surface, including using a sprayer to emulsify the oil contamination and a skimmer for trapping the oil globules on the surface. To investigate the most appropriate method for improving the SBI success rate, three different devices were evaluated in triplicate tanks. In addition to the control tanks, which were not equipped with any surface-cleaning device other than overflow mesh, two sprayer designs (narrow, covering one-third of the tank's diameter, versus wide, covering the tank's entire diameter) and an air-blowing surface skimmer were set for a 16-d trial. Freshly hatched larvae (7,000 per tank) were divided into four treatment groups in twelve 250-L larval nursing tanks that shared a common recirculation system. Significantly higher rates of SBI were found in the tanks that were equipped with a wide-covering sprayer (30.6 +/- 13.0%) compared with the control, skimmer, and narrow-covering sprayer groups (14.7 +/- 7.5%, 4.8 +/- 1.7%, and 12.2 +/- 5.1%, respectively). Thus, the results of the present study indicate that the sprayer design that covers a large portion of the tank's diameter is an appropriate solution for enhancing SBI rates in Zander larviculture.