Credit: Kevin Fitzsimmons (USA)
It should be noted that the series of raceways shown in this photo were original designed for catfish studies but later and for economic reasons, the operations were stocked with tilapia.
The following descriptions were developed by the author and found in the reference below. The first facility is located near Abasolo, Tamaulipas. The raceways were built in a series of stair steps with 17 reuses of the water. The design was based loosely on a system developed for catfish by Leo Ray of Idaho. The vertical drops are sufficient to replace oxygen in the raceways, but there is no mechanism to remove ammonia from the water. That metabolite accumulates in the water and reduces growth of the tilapia.
The managers of the demonstration farm leave sections of raceways open to allow for solids settling and some natural dissipation of ammonia which allows some production in the lower raceways, but much of the facility is underutilized. When stocked heavily, the raceways were found to be effective for controlling unwanted reproduction and for ease of feeding and harvesting. One of the problems encountered was that the fish had a tendency to congregate near the head of the raceway where the oxygen levels were highest. Any uneaten feed would then be pushed to the opposite end and begin to decay. Another problem was jumping. The tilapia would jump from one raceway to the adjoining raceway, thereby mixing up the inventory. They would also expend considerable time and energy attempting to jump up the waterfall to the higher raceway. A final problem with the raceways was that the sides were convenient for fish eating birds to perch.
This operation –like similar others- was redirected towards tilapia when US prices for catfish fell and tilapia prices in Mexico and the US stayed relatively constant.
Reference: Fitzsimmons K. 2000. Tilapia aquaculture in Mexico. Pages 171–183 in B.A. Costa-Pierce and J.E. Rakocy, eds. Tilapia Aquaculture in the Americas, Vol. 2. The World Aquaculture Society, Baton Rouge, Louisiana, United States.
