Effects of sub-lethal concentrations of NPK (15:15:15) fertilizer on growth and feed utilization by the toothed carp Aphyosemion gairdneri under laboratory conditions

Abstract

The effect of sub-lethal concentrations of NPK (15:15:15) fertilizer on growth and feed utilization by the toothed carp, Aphyosemion gairdneri was investigated under static bioassays during an eight week exposure period. The concentrations of the fertilizer used were 0.50, 0.25, 0.125, 0.063 and 0.031 g/l. Weight of the exposed fish decreased proportionally with increase in the fertilizer concentrations. However, at 0.0312 g/l, no significant weight loss (P > 0.05) was observed. With the exception of the groups of fish exposed to 0.031 g/l, the fertilizer led to poor food conversion ratio (FCR) and protein efficiency ratio (PER). The groups of fish exposed to 0.50 g/l almost rejected the food offered and consumed less than 40% of food offered, these groups recorded a 100% mortality before the end of the eight week exposure period. Environmental implications of the results are discussed.


Key words: Inorganic fertilizers, growth, Aphyosemion gairdneri, pollution


Journal of Aquatic Sciences Vol.18(2) 2003: 101-104