Researchers:
Edgardo H. Lasangre Sr.
Naida G. Lasangre
Abstract:
Aquacuture or the farming of aquatic organisms, is achieved through the manipulation of an organism’s life cycle and control of the environmental variables that influence it. Three main factors are involved: control of reproduction, control of growth and elimination of natural mortality agents. Control of reproduction is essential otherwise farmers must rely on naturally spawning stocks. The supply of fry from the wild may be restricted to particular season and a particular area and there may also be shortages due to over-exploitation of wild stocks. Growth can be increased through feeding. While the culture of carnivorous species is dependent upon the supply of largely fish-meal diets, there is considerable scope for minimizing feed costs providing that the appropriate omnivorous/ detrivorous / planktivorous species and system are used.
Finally, rearing systems are essential to all types of aquaculture. They are designed to hold organisms securely while they increase in biomass by minimizing losses through predation and disease and by excluding competitors. Rearing systems must also facilitate management.
Rearing facilities for fish can either be land-based or water-based, the farmer including ponds raceways, tanks and silos and the latter comprising enclosures, pen and cages.
The term “enclosure” pen and cage appear synonymous and may be used interchangeably. However, in aquaculture this has given rise to a degree of confusion, the term “enclosure” often being used to describe something which could either be a cage or a pen and the word “pen” being used to denote large sea cage. “Enclosure” is used to denote an enclosed natural bay, where the shoreline forms all but one side, which is typically closed off by a solid, net or mesh barrier. In pen culture, all sides of the structure except for the bottom are man-made, often being constructed from wooden poles and netting. The bottom of the pen, however, is formed by the sea bed. Cages, by contrast, are enclosed on the bottom as well as the sides by wooden, mesh or net screens.
There are other differences among water-based rearing facilities. Pens and enclosures tend to be larger ranging from around 0.1 ha to some that exceed 1000 in ha area. Cages, however, typically have a surface area somewhere between 1m2 and 1000m2. Moreover, because of their small size, cages are better suited to intensive methods than pens.
Traditional cage culture, distinguished by its reliance on natural construction materials and natural or waste feeds. However, these traditional cage-rearing practices had a localized influence and did not directly give rise to modern cage fish farming methods. Modern cages utilize synthetic polymers and metals, although wood is still widely used in many designs. It is difficult to be precise about the origins of modern cage fish farming although Japan uses undoubtedly a key influence.
The floating cages that will be installed in the pond are made up bamboo poles framed provided with Styrofoam floaters, hang with the net for of 20 breeders to reproduce ad nylon rope for tying to prevent the cage from moving in the different positions.
There are four cages to be installed five males and 15 females breeders in each cage. A number of tilapia fry will be determined in each cage to determine the reproductive capacity of Tilapia nilotica breeders in a floating nets in pond.