Abstract

Omofunmi O.E., and Olorunnisola O.A

The investigation was carried out to identify and proffer solutions to some environmental and management problems that have hitherto affected fish production sub-sector of the economy, using Lagos State, (Western) Nigeria as a case study. It was observed that the maximum temperature in the study area ranged between 27.6 OC and 31.8 OC in February, while the minimum temperature ranged between 23 OC and 26.8 OC with the least being in July. Values of water loss from ponds resulting from evaporation and seepage ranged from 2.5 – 4.6 day-1.. Percentage reduction in pond water depth during dry season ranged from 70 – 81 % as compared to the observed percentage increase during rainy season with range of values as, 17 – 34%. The mean rise and fall in water depth were 24.7 ± 3.8 % and 47.6 ± 11.7% respectively. The fall in water depth during dry season was almost twice its rise during rainy season. The degree of variation among ponds was found to be significant (t=2.11 at p = 0.05). The mean rate of soft sediment depth was 10.5 ± 1.8 cm yr-1 , while the soft sediment depth in silty sand ponds doubled those from mixed sandy ponds. The predictive equation indicated that soft sediment accumulation was found to increase with year of pond operation. The results showed significant correlation (t = 1.988. p = 0.05) between soft sediment and year of pond operation. Long hydraulic residence time averaging 250 days in the ponds investigated enhanced high level of organic stimulations.