نوع مقاله : مقاله پژوهشی
نویسندگان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
In the years 2001 and 2002, two great floods occurred in the Madarsoo River in Golestan National Park, north-east of Iran. To study the effects of these floods, we assessed the age, growth and reproduction of Capoeta capoeta gracilis (Keyserlhng, 1861) in the river from November 2003 to December 2004. Fishes were caught by electroshocker and 1025 specimenswere randomly selected from the catch. Growth in length was expressed for both sexes with Von Bertalanffy equation. Growth parameters were estimated as L¥=249mm, K=0.22 per year and t0=-0.30 year for males and L¥=306mm, K=0.21 per year and 10=-0.38 year for females.
The length-weight relationships were described for males as ln W= -4.48 + 3.03 lnTL and as lnW= -4.59+3.0551 lnTL for females which shows a good feeding condition and a positive-isometric growth. Difference of length distribution between males and females is significant and males have lower lengths because this sex matures sooner so its growth is lower than females. Difference of fish length distribution between this study and previous studies on the c.capoeta gracilis of the river is significant and Lenkoran's length shows great decrease in this study as compared to previous studies. Age of the fishes ranged from 1+ to 5+ formales and 2+ to 8+ for females, the dominant age was 2+ and the mean age was calculated as 2.009±0.034.We found that C.c. gracilis population had become younger in this study, so we concluded that the floods had made great changes in age and length structure of the fish. Male to feplale ratio was 1.5±1.0 (P<0.01), the mean fecundity was 3116±l387 ova per female and maximum gonadosomatic index for both sexes occurred in June. We found no significant difference in the reproductive characteristics of the fish as compared with studies conducted before the floods.
کلیدواژهها [English]
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