Age, growth and reproduction of Chondrostoma regium (Heckel, 1843) from the Zayandeh Roud River, Iran

Age, growth and reproduction were investigated for Chondrostoma regium, collected monthly (November 2007- August 2008) from the Dimeh Spring region, Zayandeh Roud River, Iran. The maximum age of collected female and male fish were estimated based on scale increments as five and four years respectively. Von Bertalanffy growth equations were calculated as Lt=246[1-e^-0.206(t-0.034)], Wt=163.29[1-e^-0.206(t-0.034)]^2.77 for females and Lt=253.1[1-e^-0.206(t-0.175)], Wt=188.25[1-e^-0.206(t-0.175)]^2.99 for males. Size ranges of the male and female specimens were almost similar. The fork length range for females was 10.5-18.0 cm and 10.7-19.7 cm for males; and the weight range was 15.7-85.4 g in females, and 14.5-88.5 g in males. The female-male ratio was 1.8:1 (p<0.05), and for both sexes gonadal development and sexual maturity occurred in the second year of their life. Length-weight relationships revealed isometric growth pattern for males and a negative allometric growth for females. Monthly data of Gonadosomatic Index, and ovary condition suggested that spawning occurred during May and June. The mean absolute and relative fecundity was calculated as 2429±1512 (eggs/female) and 78.1±18.7 (egg/g), respectively, and fecundity was significantly correlated with both body weight (r^2=0.90) and fork length (r^2=0.84)

The effects of different concentrations of probiotic Saccharomyces cerevisia on growth performance and survival rate of rainbow trout (Oncorhynchus mykiss), fry and resistance against salinity

In the present study, a yeast strain Saccharomyces cerevisia var. elipsoidous, acting as probiotic, was administered to rainbow trout (Oncorhynchus mykiss Walbaum, 1792) fry during a period of 21 days and the effects of the yeast on improvement of growth and resistance against environmental stress were evaluated with respect to fish fed on yeast free feed (control group). The control treatment consisted of a standard commercial diet, and the treatments consisted of the control diet supplemented with 0, 1, 5 and 10% yeast (w/w). The results demonstrate the beneficial effects of probiotics on the characteristics of rainbow trout, as the Specific Growth Ratio (SGR), body weight gain (%BWG) and protein conversion ratio (PER) in 5% yeast-fed fish were significantly (P&lt;0.05) enhanced by probiotic administration. On the contrary, no effect on the fry growth performance, mortality, condition factor (CF), food conversion ratio (FCR) and histological assessment was shown. A significant (P&lt;0.05) increase in lipid content of the carcass was detected in diets with probiotic compareD to 0% and the control treatments. Ash and protein contents of the carcass increased and decreased with an increase in yeast amount, respectively. Challenge with different levels of salinity (10 and 15 ppt) after 24 h revealed 100% survival in treatments containing yeast as probiotic, and difference with control group was significant (p&lt;0.05) indicating that S. cerevisia could enhance the resistance against salinity stress. Addition of yeast in concentration of 5% to the diet is recommended during the early period of rainbow trout fry farming to achieve the best results on growth performance and feed efficiency.Keywords: Saccharomyces cerevisia var. elipsoidous, Oncorhynchus mykiss, probiotic, survival and growth rate, carcass qualityAfrican Journal of Biotechnology, Vol. 13(10), pp. 1160-1168, 5 March, 201

Growth and reproductive characteristics of Squalius Lepidus Heckel 1843 in the Dimeh spring of Zayandeh-Rud River

Population structure, growth, and reproductive characteristics of Kavar, Squalius lepidus, a native species of Cyprinidae family in Zayandeh-Rud River were investigated by monthly sampling from October 2006 to August 2007. A total of 415 individuals were collected. Age groups of males and females ranged between 1+ and 4+ . The male:female sex ratio was 1:3. The largest female was 163.0mm in fork length and 63.71g in weight; whereas the largest male was 156.0mm in fork length and 50.45g in weight. The minimum, maximum, and mean absolute fecundity was 1161, 12953, and 4279±2169, respectively, and relative fecundity was 148.4±49.3 eggs/g of body weight. Gonadostomatic Index (GSI) values suggested that spawning of Squalius lepidus occurs from May to June. Thus, Squalius lepidus is considered an intermittent spawner species. Growth parameters for both sexes were stated by the vonBertalanffy growth function as k = 0.162, L = 232mm, to = -0.427 years for females and k = 0.136, L =217mm, to =- 0.847 years for males. The weight-length relationship was described as W = 0.00005L 2.827 (r2= 0.860) for males and W = 0.00005 L2.855 (r2 = 0.859) for females. The slope of the regression line (b) fitted through the weight-length data suggested a negative allometric growth for both females and male (P<0.05)