Iranian Scientific Fisheries Journal
Year:2003 | Volume:12 | Issue:1|Papers Count:11

The variations of pH, alkalinity, salinity and hardness were measured and compared in different sampling sites in headwaters of Hanna river and Hanna reservoir and its outflow.The results showed that the headwaters were saline and hard and had relative higher alkalinity with stable pH. But due to extended biological activities exerted by lentic condition, the salinity, hardness and alkalinity were modified in the reservoir. The pH of the water column of reservoir were not constant and showed significant daily and annual changes and reached to a high mean value of 9.7 in mid summer. The magnitude values of above mentioned chemical parameters in the Hanna river, or in the other hand, in outflow of reservoir were usually lower than reservoir and higher than headwaters.Apart from existence of hot summer and very cold winter days, there were no observed thermal stratification in the water column of the reservoir. In summer, the stratification was eliminated by the blowing of severe winds in addition to hydraulic pressure exerted by waves of larger and shallower area of the reservoir on smaller and deeper part and on the other hand, in winter the stratification of water temperature can be observed because of calm weather and freezing the reservoir surface.

In regarding to study the fecundity and feeding behaviour of Barbus xanthopterus in Karkheh river and Hoor-al-Azim marsh, 393 specimens of this species were collected monthly by drift gillnet, set net and castnet from October 1996 to September 1997.The bottom substrate of marsh was silty-clay and in some points it was sandy. Seventeen types of benthic invertebrates from 6 orders were identified, among which insects had the highest density and diversity. Maximum and minimum absolute fecundity was 549211±7295 and 136924±652 and for relative fecundity they were 142.53±1.95 and 18.886±0.O9 for each gram of body weight, respectively. Absolute and relative fecundity showed the highest correlation with girth and fork length, respectively. Feeding intensity did not show a regular trend and intestine fullness in river fishes is more than that of Hoor-al-Azim which was an indicative of active feeding in Hoor-al-Azim and migration to the Karkheh river for spawning. Main food item was invertebrates and plants and relative index of intestine and its contents showed that B. xanthopterus is an omnivorous species.

This project was carried out in the Khoor-e-Musa creek near Bandar Imam Khomeini from December 1996 to February 1998, with a view to studying the abundance and dominance of the Copepod community in the area. Monthly sampling was done in four stations from December 1996 to September 1997 and subsequantly samples were collected from al11he stations also in December 1997 and February 1998. Horizontal and vertical samplings (from 20 m depth to the surface layer) was carried out.Totally 16 genera of planktonic copepods were observed, of which, 11 genera belonged to Calanoida, 2 genera to Harpacticoida and Poecilostomatoida, and one genus to Cyclopoida.The most dominant genera was Acartia with relative abundance of 75.9% and the least dominant was Corycaeus with 0.002%. ANOV A did not show any significant difference in abundance among the stations. But among months ANOVA showed significant differance (a = 0.05). The peak density was observed in May. The T -test showed significant difference between column and surface densities only in February 1997 (a = 0.05). Temperature, pH, D.O and salinity in four sampling stations showed no significant differences. But ANOV A showed significant differances for pH and temperature (a=0.05), in different months.

Primary studies of this project began in winter 1996. After an experimental cruise, main sampling stations were determined and through six cruises the fishes of Jarahee river collected from headwaters in Khouzestan and Kohguilouye & Boyerahmad provinces to Shadegan lagoon. Through the 11 main stations, 1135 specimen of fishes were collected by castnet, gillnet, electroshocker, hoke & line and river-trawl.Collection process had conducted during May, June, August, September, November of 1997 and February of 1998.After one year laboratory studies, collected fishes were identified by some ichthyologic methods. Identified fishes (20 genus and 27 species) belong to nine families of Bagridae, Balitoridae, Cyprinidae, Heteropeneustidae, Mastacembelidae, Mugilidae, Poecilidae, Siluridae, and Sisoridae.

This study was carried out to determine artificial breeding normatives of Russian Sturgeon (Acipenser gueldenstaedti). In this research, which was conducted in Shahid Marjani Breeding Center in late winter, 27 female and 13 male broodstocks were used. All broodstocks were provided from Turkeman and Mianghaleh fishing ground in the Caspian Sea. After maintaining them at Kurinski ponds and determination of germinal vesicle in the oocytes, 15 female and 13 male broodstocks were injected by 60-75 and 40-55 mg of pituitary hormone, respectively. After maturity duration, 10 female and 5 male broodstocks showed response to the hormone injection. Some parameters such as maturity duration, number of oocytes per gram, oocyte diameter, weight and bodymass of oocyte, motility and density of spermatozoid, duration of reaching to 4 and 16 divisions, incubation duration, fertilization percentage in each stage, mortality rate during incubation, number of larvae resulted from each broodstock, number of larvae per gram, weight of each larvae as well as some morphometric parameteres and age for each broodstock were determined.

The present study was conducted on a large number of oocytes collected from 36 female Acipenser stellatus brood fish caught from fishing grounds in the Guilan province and transferred to the Shahid Behesti Sturgeon Breeding Center during 1997-1998. Physiological assessments were carried out on the microscopic sections prepared from these oocytes.Under normal conditions, 9 distinguishable layers were observed in the sections prepared from A. stellatus oocytes that included the follicle, the outer most layer, followed by a jelly coat, an external zona radiata, internal zona radiata, fat layer, pigments, cytoplasm, nucleus and nucleoli. The presence of erythrocytes and micropyle canal in the oocytes indicate normal embryognesis among them.

In regard to study the distribution pattern of phytoplanktons (with emphasize on chrysophyta and pyrrophyta), a series of 4 cruises were carried out seasonlly in 1996. A total of 93 species belong to 2 main phyllums of chrysophyta (mainly diatoms) and pyrrophyta were identified consist of73 and 20 species, respectively. The diatoms have an important role in the whole Caspian Sea from point of species diversity and on the other hand contain the most abundance and biomass in all seasons.There are two main species of Rhizosolenia calcaravis (belong to chrysophyta) and Exuviealla cordata (from Pyrrophyta) inhabit in the southern Caspian Sea. Comparing the density and biomass of different phyllums of phytoplanktons showed that chrysophyta with 75% and pyrrophyta with 17% are the most abundant phytoplanktons in the said region.

In this study 60 samples were collected from the southern Caspian Sea and some rivers of Mazandaran and Guilan provinces. Genetic variation and probable population differentiation of Barbus capito were studied based on the mitochondrial cytochrom-b gene. The mitochondrial DNA was extracted from fish fin using phenol-chlorophorm method. The specific primers were designed for B. capito and the PCR experiments were done on 60 samples. 11 restriction endonuclease enzymes were applied for RFLP analysis (ALuI, AvaI, AvaII, HinfI, DdeI, HincI, HpaII, RsaI, Sau3AI, HaeIII, TaqI). PCR products (1062 pb) and DNA digests were subjected to agarose and polyacrilamid gel electrophoresis to seperate fragments according to their molecular weight. These patterns were identified similar fpr all samples. Regarding to this patterns, it can be seen that polymorphysm phenomena cannot be observed by above mentioned enzymes and cytochrome-b gene, and there is no seperate population of B. capito in the southern Caspian Sea.

In this study, gametogenesis of sharp-nose mullet (Liza saliens) was investigated bassed on morphological and histological characteristics. For this purpose, about 150 specimen of this species were collected from beach-seine nets in the southern Caspian Sea and were transferred to the laboratory for futher examinations on gonads. The gonad development was classified to 6 different stages consist of: stage I: The oocytes small, colourless with a big nucleus.stage II: The low increase in size of oocytes; globular yolk of nucleus appearing.stage III: Blood vessels are appearing on the ovary; the oocytes are in the primary vitellogenesis stages; vacules and zona radiata are seen around them.stage IV: The ovules can be easily observed with naked-eyes, vitellogenesis are complete and oocytes are mature.stage V: Oocytes are in maximum growth, nucleus migrating towards animal pole; spawning occures in this stage.stage VI: This stage is after spawning, ovary contains empty follicles.Based on this study, the stage of I to III were observed in August to April; stage of IV in May and June; stage of V in June and July and stage VI in August.