Fish production in periphyton based organically manured seasonal wetland fish ponds ‘Fingerponds’ in Uganda

This research investigated the enhancement of fish production through the application of organic manure and presence of artificial substrates in eight 192 m -2 seasonal wetland earthen ponds ‘Fingerponds’ over two grow-out periods between 2003 and 2005. The ponds were predominantly stocked with tilapia (Oreochromis spp.) at densities of 0.1 to 0.5 fish m -2 . Chicken manure was applied fortnightly at low (521 kg ha -1 ), medium (833 kg ha -1 ) and high (1,563 kg ha -1 ) levels in the first period and at only low levels in the second period. Artificial substrate mats made from Phragmites, Raphia and bamboo were installed for six weeks in selected ponds in two locations and covered an area equivalent to 31%, 43% or 70% of the pond surface. Periphyton ash content ranged from 21 to 59 %. Periphyton productivities ranged from 0.01 to 0.90 g C m -2 d -1 resulting in more than doubling of the total primary productivity (periphyton + phytoplankton). Higher net fish yields were obtained in manured ponds in the presence of periphyton substrates and were significantly different (P