June 13, 2011
Trophic ecology is essential to understand ecosystem functioning and structure and assist biological conservation. Here we investigate, for the first time, the feeding ecology of Aphanius farsicus, a cyprinodontid fish endemic of a single landlocked river basin in central Iran. We sampled monthly a population of this fish species during a year and examined differences in food across seasons, sexes and sizes. Similarly to other cyprinodonts, A. farsicus showed sexual dimorphism and more abundance of females. Size structure and individual condition varied across seasons, with larger fish in spring and better condition in summer and less in winter. We found no empty guts, suggesting that these fish feed all year round due to the warm climate of its native distribution. Farsi toothcarp diet was based on detritus, algae (particularly diatoms, green algae, and cyanobacteria), and small invertebrates. Seasonal variation in diet was more important than variation due to fish size and the Farsi toothcarp consumed more green algae in spring and early summer and more diatoms and insects the rest of the year. Herbivory was considerable, similarly to a few other cyprinodonts, and increased with fish size, particularly because of higher consumption of green algae. As with species composition in diet, season was more important than size in the variation of number, biovolume, mean size, and diversity of prey captured, with higher number, richness and size of prey captured in summer. The ontogenetic diet shift was less marked in this cyprinodont than in many other Aphanius species, probably due to its reduced size and the resource availability of its habitat, but was also shown by size-dependent feeding selectivity for a few invertebrates.
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.
January 29, 2012
June 13, 2011
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