Iranian Scientific Fisheries Journal
Year:2001 | Volume:10 | Issue:2|Papers Count:7

In order to study the growth rate of stellate sturgeon, three earthen ponds with 2 hectares area were selected randomly. Two ponds were treated with 16 tons organic fertilizer and 40 kg Daphnia. The total culture period was considered 35 days. The physical and chemical parameters of water and also the density of zooplanktons and benthos were measured during the rearing period. Apart from these factors the gastrosomatic index (GSI), daily growth rate and the condition factor of the fingerlings were also determined in order to assess the output of each pond. On the basis of the statistical analysis conducted, no significant difference was observed in the physical factors of the water in the three ponds but for nitrite values were significant.The major productivity of zooplanktons and benthic organisms were Daphnia (D. magna and D.pulex), cyclops and nauplii of cyclops.

The 0bjective of this investigation was molecular population study on Penaeus semisulcatus stocks from the Persian Gulf and Oman Sea. Samples were collected using trawling method from Hormouz (40 individuals) and Bushehr (35 individuals) regions.The DNA of samples were extracted using Phenol and chloroform method and then were amplified using a pair primer of Cytochrom Oxidase subunit I (COI) gene sequences by a thermal cycler. Nine restriction enzyme were used to digest the target gene region that five of them (AluI, HinfI, HincII, HpaII and RsaI) appeared Polymorphic patterns. Reap software and X2 test were used to analyse the RFLP data.The average of nucleotide diversity and haplotype diversity among the population were 0.0345720±0.0011952 and 0.28590±0.08174 and nucleotide divergence among population, being studied, is supposed to be 8.5%. Considering the results, dispersion of haplotypes in two regions showed a significant difference and this is an evidence for proving the variety of the stocks.The minimum and maximum biomass of zooplanktons and benthic organisms in the ponds treated with fertilizer and live-food were estimated 0.018 and 38.63 g/m3; 0.0 to 2.1 g/m2, respectively. No significant difference was observed in the productivity of the ponds. On the basis of the abundance of prey in the studied ponds, D. magna and D. pulex were the primary prey (Fp>50), cyclops and tlauplii of cyclops were secondary prey (10< Fp<50) and Tubificidae and Chironomidae were the occasional preys (Fp=O). The results of GSI observations indicated a decrease in daily growth rate and condition factor with an increase in weight and length of the fingerlings, but this difference was not significam. The analysis of gut contents of the 120 fingerlings in the ponds treated with animal fertilizer and live-food indicated that 30 of the fingerlings were reared under good rearing conditions

The purpose of this research was to evaluate the quality of preserved kilka for. human consumption. The different preservation methos (CSW and crushed ice) were used and the results were compared with the traditional method.Two main parameters (TVN and Histamin) of collected samples were measured in different preservation-time, namely: a) Time zero (after fishing), b) T5 and TI0 (5 and 10 hours duration from fishing ground to proccessing room). The mean value of Histamin of TI0 (10 hours after fishing) for traditional, CSW and crushed ice methods were determined 10.3, 2.2 and 1.5 mg/l00, respectively. On the other hand, the measured TVN values for above mentioned methods were 22.3, 19.0 and 17.0 mg/l00, respectively.The results showed a significant difference between the traditional method and two other methods (P<0.05) but there was no significant between CSW and crushed ice methods. Since, the preserved kilkas in the CSW showed higher quality, therefore, it is proposed that for using kilka as human consumption, they showed be preferably preserved in chilled sea water after fishing.

During two different periods (from 1994 to 1995 and 1997), the identification of fish fauna of Arass reservior and its Iranian tributaries were carried out seasonally. Different fishing gears, namely: gillnet, beach seine, castnet, electric-shocker were used to catch fishes in 18 stations within 6 regions.The main purposes of this study were: species identification, spatial and temporal distribution and also to determine some ecological and biological characteristics of fishes. In the present study, 27 species belong to 6 families and 4 orders were identified. From point of species composition, the Cyprinidae family with 77.8 percent was the most abundant and the percentage of species composition for other families were Gobiidae 7.4 % and each of following families namely: Balistidae, Siluridae, Poeciliidae and Percidae represented by 3.7%.The most abundant fishes blonged to Percidae family with 37.27%, Cyprinidae with 23.64% and Gobiidae with 28.61 %. Sander lucioperca and Neogobius kessleri with 37.3% and 27.8% of the total number of fishes were the dominant species.

The purpose of this study was to evaluate the changes of dissolved silicon concentration and biomass of diatoms in southern part of Caspian Sea. 1270 plankton and water samples were collected seasonally from 77 stations for further quantitative and qualitative analysis.The results showed that the minimum and maximum density of dissolved sillicon and biomass of diatoms were varied from 0.195 to 0.308 ppm and 33 to 179 mg/m3, respectively. As well as the fluctuation of dissolved sillicon concentration in different depths of photic zone, it was indicated that the maximum and minimum concentration of this element were found in the eastern area with 0.269 ppm and western area with 0.180 ppm. The most and the least biomass of diatoms were observed in the western and central areas with 180 and 89 mg/m3, respectively.The concentration of sillicon in offshore waters was more than coastal waters and on the contrary, the biomass of diatoms from coastal to offshore waters indicated a among catch composition, and on the other hand the least frequency in number we observed for Brbus mursa, Ctenopharyngodon idella, Hypophthalmyichthys molitrix, nobilis and Gobio persus with a total frequency of 0.5%. Among the total 27 identified species, 7 species were classified as exotic fishes should be mentioned that 8 species are reported for the first time from the stud area.

Population density, distribution and biomass of macrobenthic fauna in Chabahar Bay were investigated from May 1995 to March 1996 on a bimonthly basis. The most abundant groups were Amphipods (21.0%), Polychaetes (19.0%), Gastropods (15.7%) and Bivalves (10.6%). Maximum (13000 individuals/m2) and minimum (4600 individuals/m2) were observed in May and July, respectively.The changes in density were influenced by monsoon season of the Indian Ocean. Spatial and temporal variation in biomass were recorded for all groups seperately. The lowest biomass was observed during monsoon period (July-September) with a mean of 51.5 g dry wt/m2 and the highest in premonsoon period (March-May) with an average 164.8g dry wt/m2. Furthermore, the average biomass of total macrofauna III the survey area estimated as 109.3 (±49.6)g dry wt/m2 (corresponding to 481.0g wet wt/m2). Having these figures, the annual production of macrobenthic fauna was decreasing trend.In a conclusion, the concentration of dissolved sillicon and biomass of diatoms ould be affected by different physical parameters such as: water circulation, river currents, exchange of biogenic sediments in photic and aphotic zones. Also, there was a significant relationship between the biomass of diatoms and silicon concentration.