Polyculture of Nile Tilapia, Oreochromis niloticus, Either Confined in Cages or Unconfined in Freshwater Prawn, Macrobrachium rosenbergii, Ponds

Abstract

Polyculture of Nile tilapia, Oreochromis niloticus, confined in cages suspended in prawn, Macrobrachium rosenbergii, ponds has been shown to reduce phytoplankton densities, pH levels, and increase prawn production when compared to prawn monoculture ponds. However, as filter feeders, tilapia grazing might be more efficient if allowed free access to all portions of the water column, positively impacting both phytoplankton control and tilapia growth. This study was designed to compare the effects of confined and unconfined tilapia, in polyculture with freshwater prawns, on prawn growth, tilapia growth, algae populations, and water quality. Juvenile prawns were stocked into each of nine, 0.04 ha ponds as 60 d nursed juveniles (0.8 ± 0.3 g) at 62,000/ha. Three control ponds contained only prawns (MONO). In three other ponds, monosex (male) Nile tilapia (89.2 ± 23.6 g) were stocked unconfined into three ponds at 4400/ha (POLY‐UNC). In three additional ponds, the same size and number of tilapia were stocked but confined in two, 1 m3 cages at 100 fish/cage (POLY‐CON). Prawns were fed a sinking pellet (28% protein) twice daily at a standardized rate for 114 d. Tilapia were fed a floating pellet (32% protein) twice daily to apparent satiation for 106 d. In the POLY‐UNC treatment, average prawn harvest weight (26 g) and prawn production (1625 kg/ha) were significantly lower (P < 0.05) and prawn feed conversion ratio (3.0) was significantly higher (P < 0.05) than the other two treatments. However, there were no significant differences (P > 0.05) between the MONO and POLY‐CON treatments in terms of prawn harvest weight, production and feed conversion ratio with combined averages of 38 g, 2465 kg/ha, and 1.9, respectively. Average harvest weight and production of adult tilapia were not significantly different (P > 0.05) in the POLY‐CON and POLY‐UNC treatments averaging 485 g and 2293 kg/ha, respectively. Tilapia in the POLY‐CON treatment had a significantly higher (P < 0.05) survival rate (99.7%) and feed conversion ratio (1.5) than POLY‐UNC (90.3 and 0.8, respectively). There were no consistent trends in treatment differences (P > 0.05) among water quality variables or phytoplankton populations. Lower prawn production in the POLY‐UNC is likely due to competition for food with the large number of tilapia juveniles. Despite the use of Genetically Modified Tilapia (GMT) monosex males, several cohorts of juvenile tilapia were produced in each of the POLY‐UNC ponds, resulting in over 2500 kg/ha of juveniles in the POLY‐UNC treatment. No wild spawn tilapia juveniles were found in the POLY‐CON ponds. In summary, confinement of tilapia in cages appears preferable when tilapia are polycultured with freshwater prawn.

Polyculture of Freshwater AngelfishPterophyllum scalareand Pacific white shrimpLitopenaeus vannameiin low-salinity water

“…The production of shrimp was higher when cultured together with fish in cages. Tidwell, Coyle and Bright () observed a similar positive effect when Nile tilapia was cultured in cages with Macrobrachium rosenbergii and attributed this to two factors: reduced competition for food, and increased total pond surface area. The latter factor has often been noted in semi‐intensive pond cultures.…”

Tilapia polyculture: a global review

“…), and the effects of confined and unconfined tilapia on water quality (Danaher, Tidwell, Coyle, Dasgupta & Zimba ; Tidwell et al . ). For example, from an economical point of view, a stocking density of tilapia and freshwater prawn of 30 000 ha −1 with a ratio of 3:1 showed the best result (Uddin et al .…”

“…The polyculture of freshwater prawns with non‐carnivorous fish was first suggested by Ling (Ling ). Now tilapia have been reared with freshwater prawn (Garcia ‐ Pérez, Alston & Cortés ‐ Maldonado ; Uddin, Rahman, Azim, Wahab, Verdegem & Verreth b; Tidwell, Coyle & Bright ) and marine shrimp (Tian et al . ; Jatobá, do Nascimento Vieira, Buglione‐Neto, Mouriño, Silva, Seiftter & Andreatta ).…”

“…), so net‐isolated culture of Nile tilapia was used with the shrimp ( Penaeus vannamei ), and the prawn ( M. rosenbergii ) (Tidwell et al . ; Sun, Dong, Jie, Zhao, Zhang & Li ). The task of separating the different species at harvest was eliminated by culturing the fish in cages (Heinen, D'Abramo, Robinette & Murphy ).…”

“…(), 2 Tidwell et al . (), 3 Garcia ‐ Pérez et al . (), 4 Siddiqui, Al Hinty and Ali (), 5 Tidwell, Coyle, VanArnum, Weibel and Harkins (), 6 dos Santos and Valenti (), 7 Uddin, et al .…”