Bio-physical suitability of saline crater lakes of Western Uganda for artemia production
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Despite Artemia being the most widely used live feed for successful larval weaning and rearing, unreliable quality, not being readily available and expensive especially to small farmers hinders its use. This study explored production of Artemia using waters from saline crater lakes of western Uganda. Local Artemia production will contribute towards reducing the low survivals in hatcheries more especially for African catfish (Clarias gariepinus) by providing affordable Artemia of reliable quality and quantity to the hatchery operators. Limno- biophysical chemistry was used to identify the best suited lakes for bio-manipulation to produce Artemia. Limno-biophysical chemical findings indicated the studied lakes ranged between 0.2±0.0m and 2.3±0.3m (depth), 0.0±0.0mgl-1 and 205.0±15.3mgl-1 for salinity, 27.9±0.3°C and 34.4±2.4°C for temperature, 18.6±0.1 µscm-1 and 106.3±3.5 µscm-1 for conductivity, 1.7±0.4 mgl-1 and 6.0±1.0mgl-1 for Dissolved Oxygen and 9.6±0.1 and 11.5±1.0 for pH, with no occurrence of local Artemia resources. Other than Lake Bagusa where Anabaena circinalis was found to dominate the algal biomass, Spirurina platensis was the dominant algal biomass in majority of these lakes. Lake Kikorongo had the highest zooplankton diversity, having Brachionus calyciflorus as the most abundant (50 to 100 individuals /litre). Hatchability experiments using five commercial Artemia strains: Artemia franciscana from Great Salt Lake (GSL), A. franciscana from salt ponds in Vinh Chau (VC), Chinese strain (Chinese), TUZ Parthenogetic Artemia from Kazakhstan (TUZ) and Parthenogenetic Artemia strain from Siberia (PAS) using waters from crater lakes indicated Artemia franciscana (VC) to have significantly higher hatching percentage of 93.9±29.4 and 79.8±15.2 for lake Bagusa, 89.3±6.9 and 92.7±3.6 for lake Katwe, 83.4±10.7 and 83.5±9.1 for lake Maseche in the dry and wet season respectively (P <0.05). Bucket culture experiments of the best performing commercial Artemia strains from the hatchability experiments indicated survival and mean total length of GSL Artemia nauplii cultured at salinities of 40 and 60g/l to be significantly higher than that cultured at salinities of 80 and 100g/l. VC Artemia nauplii cultured at salinity of 40g/l was found to have significantly higher growth rate (length increment) than those at salinities of 60g/l, 80g/l and 100g/l (Asymptotic sig (2-sided tested) ≤ 0.000). Pond culture experiments showed that the highest mean total lengths of GSL and VC Artemia nauplii were 921.0µm and 923.0±91.9µm respectively when cultured at salinities of 60g/l for 10days. No Artemia nauplii were found to survival beyond day 10 of culture at both salinities of 60 and 80g/l. The mean survival of both GSL and VC Artemia nauplii did not significantly vary across the treatments (60 and 80g/l) after the same culture period in the salt ponds (Asymptotic sig (2-sided tested) ≥ 0.200). Although more research is needed to establish the cause for the high mortalities after 8 and 10days of culturing in buckets and ponds respectively, this results show that it possible to culture Artemia using waters from alkaline saline crater once these waters are bio-manipulated to favorable conditions for Artemia production.