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Fecundity is one of the important indicators of reproduction biology in fishes especially in rearing and restocking management of endangered species such as sturgeon. The fecundity of stellate Sturgeon (Acipenser stellatus Pallas, 1771) was studied in 50 specimens captured by gill net (mesh size= 100 mm) and seine net in different fishing areas along the southeastern part of the Caspian Sea from October 2004 through June 2005.Some biological characteristics of eggs (including diameter, surface-to-volume ratio of egg) and of fish (including age, fork length, weight, fecundity and gonadosomatic indices) were determined, and the relationship between them was defined. The results obtained showed that eggs were in stage F5 of development, and mean fork length, weight, age, fecundity and gonadosomatic indices were 125.26±8.01 (cm), 10.3±1.97 (kg), 12±1.34 (years), 170730±43211.11 and 20.88±3.19 (%), respectively. Also, the average egg diameter and surface-to-volume ratio were 2.92±1.44 (mm) and 2.06±0.12 (mm-1), respectively. Positive correlation was detected between egg diameter and surface, and volume, while negative correlation was found between egg diameter and surface-to-volume ratio. Weight, length and age have linear relationships with absolute fecundity and age was the best predicator of fecundity (r2= 0.848, F=27.962 and P value=0.003).

Concentration levels of 16 polycyclic aromatic hydrocarbons (PAHs) consisting of naphthalene, acenaphthylene, acenaphthene, fluorine, phenantherene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, indeno(1,2,3-cd) pyrene and benzo(g,h,i)perylene were measured in water and sediment samples collected from the southern Caspian Sea coasts at four stations of Noshahr, Freydoonkenar, Sari and Amirabad during autumn, winter and spring of 2005-2006. Also, tissue samples from five sturgeon species including stellate sturgeon, Persian sturgeon, beluga, Russian sturgeon and ship sturgeon were obtained. Samples were analyzed by gas chromatography after the extraction process and the obtained data were statistically analyzed using One-Way ANOVA analysis at confidence level 95%. The mean concentrations of PAHs in water and sediment samples were 0.004-2.946 mgl-1 and 0.024- 2.336 µg g-1, respectively. No significant difference was found in the mean concentrations of PAHs among stations and seasons of the examined samples. Also, mean concentration of PAHs in the liver, muscles, gills, kidney and gonads of five sturgeon species was 0.81-1.34 µgg-1. The results of this study show that the levels of PAHs in water, sediment and sturgeon organs were below the acceptable levels of PAHs proposed by USEPA and WHO.