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This review is started from April 2002 in Gorgan River and continued for one year. Three sampling stations along the river to the mouth of the estuary were 4000 meters away from the bridge to the village Charqly all samples were collected in this area. Four million sturgeon larvae with average weight of 3/2 grams were obtained from martyr Marjani and Vushmgir Dam farms. Over 40 days released at release stations, and 316 million bony fish fingerlings are being release that 282 million were whitefish, 25 million carp and 9 million bream from Vushmgir Dam and Syjval Bream Center within two months at the release stations in Gorgan River. At sampling stations, especially estuaries to determine the shelf life of fry in the river and to determining migration into the river as well as physical - chemical and assess the frequency and biomass of feeding materials (phytoplankton, zooplankton, and benthos) at the sampling stations in Gorgan River were studied. The entire estuary to the sea makes itself. Maximum migration happened at sunset. Average Debbi for 20-year was at the rate of 14.95 cubic meters per second. In 2002, the annual average was 20.8 cubic meters per second, respectively. Evaluation of abundance and biomass of feeding materials (phytoplankton, zooplankton, and benthos) indicates the status of the average biomass of phytoplankton in the river at the release station was 23/75 mg per liter that was highest in September and was lowest in December. Mean primary production based on a 145 mg chlorophyll cubic meters. 6 orders of benthic invertebrates were observed. Benthic including 9 families and 11 genera have been identified including groups of insects, worms, low-tar and Polychaetes, crustaceans, bivalve and gastropod. But at the release station (S2) the highest levels of benthic biomass (18/18 grams per square meter) degree of diversity of benthic organisms (12) species have largely been seen as a maximum in April and minimum in December. Also zooplankton condition, zooplankton total of 27 genera belonging to five categories, Rotatoria, Kladvsra, Coupe Pvda, Balanvs, and protozoa were identified. In general, in September zooplankton has the greatest diversity and abundance and in September and March, the lowest number is observed. Iranian Fisheries Science Research Institute Published

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).

In an attempt to recognize the harmful fishing times and locations for sturgeons, we used catch statistic to evaluate by-catch of sturgeon juveniles during beach seine fishing over the years 2001-2002 in Mazandaran Province. We found that over the fishing period, 23760 hauls were conducted during which 103000 sturgeons were caught. The highest by-catch occurred in October (37% of the catch) and the lowest occurred in January (5% of the catch). The maximum sturgeon catch per haul was 14.2 in autumn decreasing through the year with 1.26 sturgeon fish caught in each haul in spring. The species composition of the by-catch sturgeon juveniles was determined to be Persian sturgeon (54%), Stellatus sturgeon (37%), Beluga (6%), Russian sturgeon (2%) and Spiny sturgeon (1%).