Most of the tilapias produced by Nam Sai Farms are male monosex and sold at a size of 1 “(0.25 g). Transportation costs are not too expensive inside the country because they are packed at 1,000 per bag and a suitable 1 ton truck can carry up to 300,000 fish anywhere in Thailand. Transport costs become prohibitive when shipped by air to overseas destinations and, for example, only 1,400 fish can be packed in a 60 x 45 x 30 cm box to Europe.

To overcome this problem, Nam Sai can supply tiny fish fry (post-hatchery) packed at 10,000 per box for up to 40 hours of transport. These fish have not yet been sex reversed and Nam Sai can provide sex reversal diet and hapas as a “do-it-yourself-kit”, along with instruction, for all interested farms. However, only hybrid fish will be provided, unless the breeding costs are paid for a particular strain, as these fish will turn into mixed sex fish if they are not fed with reverse foods.

Nam Sai Farms produces numerous strains of tilapia which can be widely separated into Nile tilapia ( Oreochromis niloticus ) and red tilapia ( O. niloticus × O. mossambicus hybrides ). Nile tilapia grows slightly faster and is stronger, especially during early stages of rearing. Red tilapia, on the other hand, has a greater tolerance to salinity and is more suitable for coastal aquaculture or for cage culture sites located in estuaries with large fluctuations in seasonal salinity.

The process of acquiring and developing fish strains is an ongoing process in response to both the farmers and our own hatchery demands. The high number of breeders (200,000 plus) ensures that genetic variability is maintained and that inbreeding problems never occur. Some strains, such as Chitralada, are still as popular as ever, but they differ in many respects from the same strain 10 years ago due to natural and artificial selection. For example, the Chitralada strain has always been a fast grower up to 250g, but growth then slows down. This has resulted in a decline in the popularity of Chitralada in Thailand, as consumers are demanding more and more fish. This problem has been corrected by repeated selection of fish that grew rapidly to a large size under growing conditions.

Another example is the GIFT strain which was initially a very poor sire with many individual females never producing eggs at all. This made them unprofitable for the hatchery and a selective breeding operation was undertaken to improve spawning. Other genetic changes will be a natural response to the conditions under which the fish are kept in. For example, eggs are collected from the female mouth incubation kept in hapas. Fish that are nervous tend to unload their eggs during the harvest and therefore these fish are less likely to transmit their genes to the next generation. This will lead to a domestic stock more suited to human handling.

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

Some strains of fish may have intrinsic problems that can not be corrected by selection work only and so Nam Sai can stop producing them. For example, production of the Malaysian white strain was discontinued in 2003 because, despite good growth and good shape, fish were weak and survival was poor. Nam Sai still retains some Malaysian white breeders, 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 looking for top tilapia strains to replace or add to our existing inventory. Any information or supply of swine fish would be greatly appreciated.