This research project was carried out in Gulian Fisheries Research Center in 1998. For this purpose, two ponds were selected: Pond No. 1 with 450m2 area and pond No.2 with 250m2 area and then 3500 pieces/hectar of hybrids with 5-7g weight were added to the ponds. In order to determine their main food, they were fed by pelletes and grass according to their mean weight. Meanwhile, by adding mineral and organic fertilizers to the water, a suitable media including phytoplanktons, zooplanktons and benthoses were prepared for feeding of fishes. The stomach contents observations of 160 specimen of hybrids showed that this hybrid is a herbivorous fish and macrophytes were their main diet; and phytoplanktons could be considered as the secondary random food.

In this study, for the investigation of testicular structure and pattern of reproductive cycle in the male Caspian kutum, the sampling was achieved monthly from Jefrood coasts (Anzali, Guilan province, 37o27´ N; 49o 33´ E) from October 2011 to late April 2012. After macroscopic observations and photographing position of sexual organ, the male gonad sections were removed and fixed in Bouin’s solution. After applying of various steps of histological method, 5 micron sections were prepared, then stained with hematoxylin– eosin and finally were examined by optical microscope equipped with a camera. The results showed that the developmental stages of kutum testis were divided into four stages. In Stage I (early maturing), the testes were thin and contained the spermatogonia and the primary spermatocyt. In stage II (late maturing), the primary and secondary spermatocytes were the most visible cells. In matured stage (stage III), all developmental stages of spermatogenesis were observed. In stage IV (ripe), the largest volume of theabdominal cavity occupied with lobules and they were full of spermatid and DNA carrier spermatozoa. In general, the pattern of testicular growth was lobular system in the Caspian kutum and the process of sperm formation was done in the defined period from October to April.

The karyotype of hybrid offsprings from the cross- breeding of female roach, Rutilus frisii kutum, and the male grass carp, Ctenopharyngodon idella, was studied in order to understand the inheritance of parental chromosomes by using kidney tissue squashing method. The examination of 63 metaphase plates prepared from 14 hybrids specimens revealed that the chromosome number of these fish was 2n=50 and the arm number was determined as NF=84. The karyotype consisted of 7 pairs of metacentric, 10 pairs of submetacentric, 8 pairs of subtelocentric and acrocentric chromosomes (7m + 10 Sm + 8St-a). The largest chromosome in these fishes was a pair of the acrocentric chromosomes. The homology in the chromosome number of the hybrids (fishes) produced by the cross - breeding and almost the equality of the karyotype and the presence of a large pair of acrocentric chromosome in the karyotype of Rutilus frisii kutum and the hybrids produced by this cross- breeding indicates that the hybrids studied with regards to the type and number of the chromosomes are similar to Rutilus frisii kutum. Considering that this species was the female parent used in this cross- breeding, it is possible that gynogenesis has occured and thus the hybrids produced might gynogenetic.

Change in some quality characteristics of the kutum (Rutilus frisii kutum) was investigated. In this work, changes in moisture (M), total lipid (TL), peroxide value (PV), thiobarbitoric acid (TBA), free fatty acid (FFA), and heme iron (HI) and sensory evaluation (such as texture, general appearance, eye, color and odor of gills) were determined during 1, 4, 7, 10, 13 and 20 days after ice storage period. Statistical analysis showed significant decrease in all samples with regard to oxidative and hydrolitic deterioration (P<0.05). Also, sensory evaluation through indexes of eye, texture, general appearance, gill odor and gill appearance were recorded excellent to good till 4th and good to acceptable until 10th days.

To determine the acute toxicity and bioaccumulation of mercuric chloride in Rutilus frisii kutum, specimens of the fish were exposed to various concentrations of the chemical in water. We carried out ten treatments with three replicates and one control for each of the chemicals using the static O.E.C.D. method in 55 liter tanks each containing 14 fingerlings. During the experiments, the average pH was recorded as 7.8, total hardness was measured to be 255 mg/l, average water temperature was 27±1 degrees centigrade and dissolved oxygen was 7.2 mg/l. Mean LC50 values of Hgcl2 for juvenile R. frisii kutum with mean weight 1±0.2 grams were 0.102 and 0.086 mg Hg/l at 24h and 96h, respectively.The bioaccumulation values during 24h in muscle tissue, kidney and gill were 1.55, 16.1 and 22.7 mg Hg/l respectively. The values during 96h exposure were 2.8, 16.8 and 26.65 mg Hg/l in tissue, kidney and gill respectively. The bioconcentration values for muscle tissue, kidney and gill during the first 24h were 14.75, 153.39 and 216.11 after 96h were 33.8, 198.1 and 313.5 times that of the environment. These results show the bioaccumulation to be the highest in gill followed by kidney and muscle tissue. The study suggested direct relationship between mercury concentration in and its bioaccumulation in the fish organs tissue.

This study aimed to identify the food items of Rutilus frisii kutum and the feeding intensity for this species was performed in the southern coast of the Caspian Sea.Sampling was carried out at 6 times from late March 2012 until late May 2013 in the distribution areas of kutum (less than 60 meter depths in the southern coast of the Caspian Sea) and 193 fish were studied for the contents of the digestive tract. The average total length and total weight of samples which were 36.9 ± 8.5 cm and 562.9±353.2 g, respectively. The results of this study showed that kutum are generally fed from Cerastorderma sp. and Balanus sp. as the presence frequency of Balanus sp. was more than Cerastorderma sp., but the amount of its consumption was less than Cerastorderma sp. In order of importance after the Bivalvia, Gastropoda, Crabs, Fish eggs, Filamentous algae were present in kutum GI. The feedingintensity and food strategy of this species are exposed to alter in term of gender, sampling periods and longitudinal length groups. Thus, the feedingintensity in males was more than females and the length groups in smaller than 30 cm was more than in higher length groups of 30 cm (P<0.05). Also the feeding intensity was shown in the different sampling periods as the reproductionperiods was drastically decreased with reducing temperature and in late winter. (P<0.05). At the recent survey, the results are indicated that the influence of adaptation and behavioral mechanisms, physiological and ecological, such as Bivalvia has a pivotal role for feeding of kutum, but the diversity amount on food consumption and feeding from Bivalvia were less than last years. If this species was surveyed in the southern coast of the Caspian Sea, it was appeared that this species was mostly fed on Cerastorderma sp., while it is recently demon strated the above prey was general food for kutum. It seems that releasing of fingerling kutum was mostly carried out by artificial propagation and its stock increasing was caused to decreasing frequency this food.

The present research aims at identifying various stages of Rutilus frisii kutum sexual maturity with emphasis on reproduction time’s body size at maturity, sex determination and fecundity through application of various scientific methods done during 2005-6. With respect to the central importance of kutum among the south Caspian sea fishes, it seems necessary to launch a comprehensive study including, consideration of biometrics menses enumeration such as total length, fork length, standard, total body weight, gonads weight, number of ovum per gram and the sexual maturity of this species at different periods and location. For this purpose the Kutum fishes migrating to estuaries and reverie sections were regularly caught by beach seine with mesh size of as 22mm.on a monthly basis. The data obtained were analyzed using Excel, SPSS 13 software packages using statistical procedures such as ANOVA.The results indicate that during March, April & June the female Kutum were at IV, V, VI stages of sexual maturity whereas the maximum range occurred in March when the body length of the fish was 349±58 mm weighting 564±334 with a sex composition of 45.6% female and the remaining 54.4% constituting male ones.

Rutilus frisii kutum is one of the most important and economic fish in our country. Since the passage of time and temperature on the quality of fish caught continuous reduced, so decreasing the temperature by ice storage, immediately after fishing, is a good method to avoid loss of quality fall. In this study change of some quality parameters of R. frisii kutum during ice storage for 16 days such as expressible moisture, pH, thiobarbituric acid, total volatile nitrogen, free fatty acid, psychrotrophic count and total viable count to assessment the effects of delay of putting ice on fish caught and loss in quality product was measured. According to these results, the chemical and bacterial indicators were increased significantly during the storage in ice. Delayed icing caused the higher degree of oxidation. Furthermore, delayed icing, lack of attention to correct method of storage, and ice storage for a long time can decrease the quality of meat. It is better that fish be ice storage after fishing immediately. Shorten the shelf life of the product on the ice and accelerate cooling, helps to increase the shelf life of the product.

The early morphological development and allometric growth pattern of Caspian kutum (Rutilus frisii kutum) during early development (from 0-35 days post hatch=dph) was studied. Morphological data were obtained using ImageJ software from 2D pictures and allometric growth patterns were computed based on Log10 y= Log10 a+bLog x function. Based on inflexion point of morphological traits and body shape changes, the early developmental of kutum were divided into Eleutheroembryo, Propterygio-larval, Pterygio-larval” and younger juvenile phases, each of which included vital developmental events. Rapid and intense changes occurred during Eleuthero-embryo and Propterygio-larvae stages such as development of gills, depletion of yolk-sac and exogenous feeding, development of feeding apparatus, sense organs and organs related to swimming performance. The results also revealed that developmental changes occurred in agreement with the inflexion points of morphological characters and their developmental priority imply on functional importance of feeding, respiration and swimming related structures.