Reproductive biology of the Geno hot spring tooth-carp (Aphanius ginaonis Holly, 1929) in southern Iran

Abstract

This study provides fundamental information on some key aspects of the reproductive traits of Aphanius ginaonis, an Iranian endemic, poorly studied cyprinodontid fish species. Samples were taken monthly, from March 2010 to February 2011, from Geno hot spring (Bandar Abbas, Iran). The smallest sexually mature male and female individuals measured 21.1 and 15.1 mm and massed 0.15 and 0.06 g, respectively. The overall sex ratio (females/males) found to be 1.18. Monthly sex ratios suggested no significant differences, although females demonstrated significantly higher abundances than males at larger length classes. Gonadosomatic index and ovary condition suggested that species reproductive period lasts all year. Oocyte diameter ranged from 0.30 to 2.20 mm, with a mean of 1.15 ± 0.49 mm. Monthly mean oocyte diameter were not significantly different, ranging from 0.99 (in February) to 1.22 mm (in December). Size composition analysis of oocyte diameter showed that females contained mature oocytes (>1.1 mm) throughout year. Absolute fecundity of A. ginaonis ranged from 36 to 832 oocytes per individual (mean: 341 ± 209 oocytes), varying considerably at given length and mass. Relative fecundity to total length fluctuated from 12 to 169 oocytes/mm (mean: 78 ± 41 oocytes/mm) while relative fecundity to total mass varied from 61–526 oocytes/g (mean: 213 ± 106 oocytes/g). A. ginaonis is an asynchronous, iteroparous spawner producing more than one oocyte clutch in a single reproductive season.