Credit: Ahmed Hegazy (Egypt)
The photos were taken in a commercial tilapia hatchery in the Philippines. The practice shows the grading of tilapia fry after the completion of the sex reversal process which is done in hapas in which 17ᾳ methayl testosterone is used for 21 days. The grading is an important practice in tilapia hatcheries and targets to produce different size groups of sex-reversed tilapia fry prior to their stocking in grow-out units. Minimizing the variation in stocked fry helps in the management process as well as in the marketing of produced fish. The photos show the net graders with different mesh sizes are used in the grading process. The cage with the wider mesh is used first through which larger size tilapia is retained while smaller tilapia are allowed to pass through and captured by a smaller mesh containment to enable moving the passed-through fry to a second cage grader of medium mesh size and the same process is repeated ending by three size groups of tilapia to be stocked in grow-out facilities.