Assessment Of Water Qualityin Aquaculture Ponds In Tigoni, Kiambu County, Kenya

ABSTRACT

Fisheries and aquaculture is an important source of food, income and livelihoods for hundreds of millions of people around the world. Aquaculture production has increased from 29.5million tonnes in 2010 to37.5 million tonnesin 2014 in the world and 1.3 million tons in 2010 to 3.8 million tonnesin Africa.  There is no sufficient information suitability ofwater quality in aquaculture ponds in Tigoni. The aim of the study wasto determine the suitability of aquaculture ponds for fish farming based on their water quality.The specific objectivesof the study were; to find out quality of water in aquaculture ponds, to identify the type of algae in aquaculture ponds and to evaluate the relationshipsbetween water quality and algae in the aquaculture ponds.The study area was Tigoni in Kiambu County. Stratified randomsampling design was used to select 8 sample ponds which water samples were collected twice a month for four months.  Parameters were temperatures, pH, conductivity, dissolved Oxygen (DO), secchi depth, Biochemical oxygen demand (BOD), nitrates, phosphate and algae identification was also done.  The mean values for the physical parameters ranged from 19.69±0.480C to 22.54±0.570C (water temperature), 7.57±0.52 (pH), 190.25±127.86 to 416.50±168.93 µS/cm (conductivity), 14.13±3.36 to 28.38±7.13cm (transparency) and 4.03±1.39 to 6.63±1.37mg/l. Chemical parameter 1.99±0.52 to 2.82±0.48 mg/l(BOD), 5.06±1.05 to 57.57±15.84mg/l(phosphate) and 0.38±0.10 to 8.86±1.20(nitrates).One-WayANOVA indicated significant difference between pond F and H (P=0.001) (temperature), pond A and G (P=0.001) (pH), pond A and C (p=002) (conductivity). Pond D from G (p=0.000) (Secchi depth), pond C and G (P=0.001) (DO). Pond D and G (p=0.001) (BOD) Pond F and H (p=0.001) (phosphates) and pond A and H (0.000) (nitrates). Mean temperature were in the lower range with pond D and H being belowoptimumrange. DO t-test, pond Ghad a significant difference (t=7.500, α=0.05, p=0.00) and there was no significant difference in BOD in all ponds.A total of 12 genera of algae were identified.  Composition per pond was; pond A, B, C, D, E, F,G and H recorded 6, 10, 7,6,6,7,10 and 11 genera respectively.Temperature, lowest Pond H 6 genera identified, highest mean pond 7 genera were identified.  Phosphate, Pond H highest mean 11 genera pond F 7 genera.  Nitrates highest in pond H 11 genera while lowest was in pond A 6 genera were identified.In conclusion, water qualityin mostaquaculture ponds did not vary significantly from one pond to another and the qualityin most aquaculture ponds met qualityfor fish farming.  Ponds high in phosphates and nitrates had more genera of algae.The study recommends water management interventionbe practced to manage water qualityand control algae growthalsowater and soil conservation to control nutrient load in water sources. Researchon suitability of waterused for aquaculture in the area, a comparative study for water quality in liner and earthen ponds and the algae composition and abundance in the aquaculture ponds.……………………………………………….