Some life history aspects of Garra rufa (Heckel, 1843) in the Kangir River, Western Iran (Osteichthyes: Cyprinidae)

The present study investigated the age, growth and reproduction of G. rufa by regular monthly collections throughout one year from September 2007 to August 2008 in the Kangir River (Western Iran). Based on scale readings, the maximum ages of the population observed were 5(+) years, both sexes growing allometrically (b=2.90 (male); b=2.92 (female)). The overall sex ratio was balanced, but males were predominant in smaller sizes, and females in larger sizes. Monthly examination of the GSI indicated that the reproduction of G. rufa in the river occurred around April-May, with the highest average value of 4.21 for males in April and of 7.85 for females in May. Absolute fecundity varied from a minimum of 1,680 eggs for age 2(+) to a maximum of 13,927 eggs for age 5(+). The absolute fecundity and egg diameter to fish size (length and weight) were positively correlated. The individuals studied here arc on average smaller and have a lower weight than individuals studied in springs in southern Iran. The difference is explained by the severe ecological conditions in the river ecosystem, causing a lower growth rate and higher natural selection.