Summary Reproductive characteristics of siahmahi, Capoeta damascina (Valenciennes, 1842), a native cyprinid in the Zayandeh‐Roud River, were investigated by monthly sampling from March 2007 to April 2008. Among 689 specimens captured, the overall sex ratio was 1 : 1.57 (males : females). Males matured at age 2+. Females matured between ages 4 and 6, with 100% maturity at age 7+. Based on the gonadosomatic index (GSI), the reproductive period peaked between May and June. Histological and macroscopic characteristics of the gonad indicated the species to be group‐synchronous. Absolute fecundity varied greatly with female size, ranging 2520 to 72 650 (mean 24 800 ± 17 800) eggs for females 25.5–54.2 cm TL and weighing 320–2340 g. Fecundity increased with fish age, averages being 9446 ± 8028 for 4+ old females and 54 503 ± 13 803 eggs in mature 8+ year old females.
Aquatic environments are the ultimate sink for most of anthropogenic pollutants. The Zayandeh Roud River is the most important river in the central Iranian Plateau, supplying water to a large population. In order to determine the potential occurrence and in vivo effects of Endocrine Disrupting Chemicals (EDCs) with estrogenic or anti-androgenic properties we analyzed the wild populations of an extensively distributed endemic fish species, Petroleuciscus esfahani. For this purpose, specimens were caught from two sites upstream and two sites downstream of the expected major anthropogenic pollution sources. P. esfahani full-length cDNAs for vitellogenin (vtg), with 4177 base pairs (bp) encoding a 1339 amino acids (aa), and for β-actin (actb), with 1776 bp encoding a 375 aa, were amplified and cloned. Hepatic vtg mRNA expression levels were measured by quantitative real-time PCR. Condition factor, gonadosomatic index and sex ratio were calculated and compared with vtg expression. Gonad histology was performed to study the possible presence of intersex condition. Detection of vtg transcripts in male individuals from the two downstream sampling sites supports the hypothesis of exposure to EDCs in these regions. Higher vtg expression in male individuals, together with reduced gonad size and condition factor, in specimens from the site located downstream of the major steel mill plant suggest a major endocrine disruption in this area.
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