Myo-inositol supplement helps the performance of Seawater-acclimated Nile tilapia, Oreochromis niloticus

Seawater-acclimated Nile tilapia, Oreochromis niloticus, has been produced continuously in the Prince of Songkla University at a new campus in Chaiya District, Surat Thani, following its first breeding program (Withyachumnarnkul et al., ۲۰۰۷). The newly bred fish can survive in full-strength seawater (SW), at around ۳۰ ppt; however, the survival rate was about ۵۰% and the growth rate was about ۶۰% of O. niloticus normally reared under freshwater. The SW-acclimated Nile tilapia has been continuously stocked for research purposes in the reservoir of the AquaAcademy Farm (AAF), Tha Chana District, Surat Thani, where salinity is ۲۵-۳۰ ppt (depending on the seasons). The lower level of the survival rate of the SW-acclimated fish, compared to those being stocked under freshwater, was hypothesized as being due to the osmolality stress of the fish. It was also hypothesized that the fish that survived elevated salinity is capable to up-regulation of the gene(s) responsible for adaptation to the hypertonic environment of seawater (Gardell et al., ۲۰۱۳), as well as being able to shift the energy store in their bodies to suit the increasing requirement to fight against the hypertonic situation. With these, a series of experiments were therefore performed at AAF to test if feed supplemented with lipids of different kinds and doses, as the means to provide extra energy, could enhance the survival rate of the SW-acclimated Nile tilapia, and whether myo-inositol, the natural osmolyte (Kültz, ۲۰۱۵), could ease the osmolality stress and possibly help increasing survival rate of the fish.

Keywords:

Seawater-acclimated , survival , O. niloticus , Biomass , Palm oil , Myo-inositol