Effect of creeper shell (Cerithium sp. Bruguiere) in intensive black tiger shrimp (Penaeus monodon Fabricius) culture in closed system
1997
Krissana Rattana-r-pa
Creeper shell (Cerithium sp. Bruguiere) is frequently found in the muddy area and in shrimp ponds. This snail has a high growth rate. A comparison of the effect of creeper shell in intensive black tiger shrimp ponds indicated that within 146 days shrimp production reached 1,238.6 kg/rai with size of 27.35 grams in ponds infested with creeper shell. Survival rate was 58.29 percent and food conversion ratio was 1.90. In control ponds (without creeper shell) within 143 days production reached 1,547.4 kg/rai with size of 27.54 grams, survival rate was 73.51 percent and food conversion ratio 1.85. Comparison between ponds infested with creeper shell and the control unit showed that creeper shell ponds had lower production, lower survival rate and higher food conversion ratio. The number of creeper shell after harvesting was 875,733 shell/rai (547.33 shell/square m) with an everage weight 358.54 kg/rai. Water quality showed that total alkalinity were significantly different. Average total alkalinity in creeper shell ponds was 99.69 mg/l (54.33 mg/l-165 mg/l) and average total alkalinity in control ponds was 125.35 mg/l (85 mg/l-184 mg/l). Total alkalinity in the creeper shell ponds lower than in control ponds. Total alkalinity also varied according to creeper shell density. The result of total alkalinity with stocking density 100, 300 and 500 shell/square m was 112.6, 95.9 and 95.7 mg/l respectively. Average total alkalinity in control unit was 115.9 mg/l. This study showed that creeper veliger stage and shrimp both need alkalinity to form the shell, so the more creeper shell in a shrimp pond, the slower growth rate of shrimp. In intensive shrimp culture alkalinity has an important role in shrimp molting. The growth of creeper shells in ponds can significantly affect the culture conditions in the ponds. The methods to reduce creeper veliger stage are by using BKC 2 ppm, tea seed cake 50-60 ppm or calcium hypochlorite 35 ppm.
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