No abstract

In this research, mass production of freshwater rotifer, Branchionus calyciflorus, for aquaculture in southeastern Nigeria, using different food types (Chlorella sp., Spirulina sp and Baker's yeast) was investigated. Rotifer stock culture was prepared using Nitrogen phosphorus Potassium, (NPK) + urea (50 : 2.5 g) and chicken droppings (25 g) with freshly grown alga. Different food concentrations (150, 300, 650 and 1000 mg/ml) and feeding intervals (2x and 3x per day) were used to grow B. calyciflorus in a Batch culture method. The highest population growth was attained with 650 mg/ml of Chlorella sp. (213.81±9.94 individuals/ml), followed by Baker's yeast (196.67±8.18 individuals/ml) and 300 mg/ml of Spirulina sp. (151.90±7.98 individuals/ml). The least population growth of B. calyciflorus was recorded with 150 mg/ml concentration of Chlorella sp. and Spirulina sp. (81.43±6.19 and 75.71±5.12 individuals/ml, respectively), and 1000 mg/ml of Baker's yeast (from local market) (65.24 ±3.86 individuals/ml). The peak population growth was attained on day 8 of experiment (p < 0.05). This study indicated that both the quantity and quality of food type have significant role on mass production of rotifer for aquaculture.

The effects of short term exposure to cyperdicot on behavioural and haematological responses in 300 Clarias gariepinu swere investigated. The fish were randomly divided into three groups of 30 fish. Fish in first treatment group were exposed to tap water and served as control, while those in second and third groups were treated with 0.04 and 0.08 mg l-1 of Cyperdicot, respectively. The 24, 48, 72 and 96 h LC 50 values were1.462, 1.094, 1.030 and 0.800 mg l-1 , respectively. The safe level for the insecticide varied from 8 x 10 -3 to 8 x 10 -4 mg l-1 . Fish exposed to sub-lethal concentrations of insecticide exhibited alterations in various blood parameters including significant reductions in RBC count, Hb and PCV. A cyperdicot-induced dose-and time-dependent significant increase in W B C count from day 10 onward was observed, while values of blood indices such as MCV, MCH and MCHC in treated fish were not significantly different from those of the control group (P>0.05). This study revealed that the short term exposure to cyperdicot on behavioural and haematological responses in Clarias gariepinus elicited reduction of RBC, Hb and PCV values while MCV and MCH caused both macrocytic and microcytic anemia in the fish.