Most tilapia produced by Nam Sai Farms are male monosex and sold at a size of 1” (0.25g).  Transport costs are not overly expensive within the country, as they are packed at 1,000 per bag and a 1 ton adapted pick-up truck can transport up to 300,000 fish to any location within Thailand.  Transport costs become prohibitively expensive when sending by air to overseas destinations and only 1,400 fish can be packed in a 60 x 45 x 30 cm box to Europe, for example.  To overcome this problem, Nam Sai can supply tiny swim-up fry (post-hatchery) packed at 10,000 per box for up to 40 hour transport times.  These fish have not yet been sex reversed and Nam Sai can supply sex reversal feed and hapas as a “do-it-yourself-kit”, with instruction, for any farms interested.   Only hybrid fish will be provided, however, unless the broodstock fee is paid for a particular strain, as these fish will develop into mixed sex fish if not fed sex reversal food.

Nam Sai Farms produces many strains of tilapia that can be broadly separated into Nile tilapia (Oreochromis niloticus) and red tilapia (O. niloticus x O. mossambicus hybrids).   Nile tilapia grow slightly faster and are stronger, particularly during the early rearing stages.  Red tilapia, on the other hand, possess higher salinity tolerance and are more suitable for coastal aquaculture or for cage farming sites located in estuaries with large seasonal salinity fluctuations.


The process of acquiring and developing strains of fish is an ongoing process in response to both farmer and our own hatchery demands.  The sheer numbers of broodfish being held (200,000 plus) ensure that genetic variability is maintained and inbreeding problems never occur.  Some strains, such as the Chitralada, are still as popular as ever, but they will differ in many respects from the same strain 10 years ago due to natural and artificial selection.  For example, the Chitralada strain was always a fast grower up to 250g, but growth then slowed down.  The effect of this was a drop in Chitralada’s popularity in Thailand, as consumers were demanding larger and larger fish.  This problem was rectified by repeatedly selecting fish that grew fast to a large size under grow-out conditions.  Another example is the GIFT strain which was initially a very poor spawner with many individual females never producing eggs at all.  This made them uneconomic to the hatchery and so selective breeding work was undertaken to make spawning improvements.  Other genetic changes will be a natural response to the conditions that the fish are kept in.  For example, eggs are collected from the mouths of brooding females kept in hapas.  Fish that are nervous will tend to discharge their eggs during harvest and so these fish have less chance of passing on their genes to the next generation.  This will lead to more domesticated stock that are adapted to human handling.

For customers located 7 hours or more from Nam Sai, the risk of fry mortality during transport is higher than for local customers.  Nam Sai has a challenge test which can identify strong fish most suitable for these destinations.  If you are located more than 7 hours away from Nam Sai Farm, then please request a challenge test on your fish if they haven’t already done so.   Nam Sai will provide new fry to cover losses or return money to customers that get substantial mortality during transport due to fish of poor quality.  Customers should preserve any dead fish in formalin and should report any dead fish as soon as possible to our sales staff. 


Some strains of fish may have intrinsic problems that can’t be rectified by selection work only and so Nam Sai may stop producing them.  For example, production of the Malaysian white strain was ceased in 2003, as despite the good growth and shape, the fish were weak and survival poor.  Nam Sai still maintains some Malaysian white broodfish, and may sell them again in the future if another white strain is found that could be used to improve their viability.  Nam Sai is constantly seeking superior strains of tilapia to replace or add to our existing inventory.  Any information or offers to supply broodfish would be greatly appreciated.