Morphometrical analysis of the cichlid fish Oreochromis niloticus (Osteichthyes : Cichlidae) imported to the Czech Republic

The introduction and the morphometry of Oreochromis niloticus aquaculture r eared in the Tisova Fish Farm, Czech Republic, since 1985 is described. Thi rteen meristic and thirty-three mensural characters were assessed and analy sed, of which 7 characters of each category were used for direct comparison with literature data. A higher number of gill rakers (25-33, mean = 28.4), lower number of scales in linea lateralis (28-34, mean 30.5), shorter head length (mean = 31.1 % of SL) and greater maximum body depth (mean = 41.0 % of SL) were found. Sexual differentness in 5 meristic characters were obse rved. The analysis of the relationship between the standard length or head length and the absolute value of individual characters (in mm) has indicate d significant regressions (linear and polynomial) and correlations in mensu ral characters. Parameters of length-weight relationship and of factors of weight condition in relation with total length and standard length are also presented.