Iranian Scientific Fisheries Journal
Year:2005 | Volume:14 | Issue:2|Papers Count:17

Following a mortality of up to 40% of cultured Grass Carp (Ctenopharyngodon idella) in fish farms of Khouzestan province when water temperature was up to 20°C, samples were taken and examined for etiological clues. We observed that fish gills were coated with a gray-white mucus layer, fin was eroded and wounds were present in peduncle of the affected samples. Bacteriological studies on the samples of gills and eroded and wounded peduncle skin using Cytophaga selective medium, resulted in isolation of filamentous gram negative bacteria chemically similar to Flavobacterium columnaris.Histological observations showed the affected fish carrying symptoms including congestion, hemorrhagia, edema in base membrane, hyperplasia of chondrocyte and secondary lamellae cells, fusion of lamellae, necrosis and peeling of secondary lamellae and also presence of filamentous bacteria in gill tissue sections. Necrosis of skin layers and expansion of ulcer to underlying muscles, degeneration of muscle cells and necrosis of muscle bundles were seen in peduncle muscles. We did not find this bacterium in internal organs. We conclude that the isolation of the bacterium and observation of histopathological changes suggest the organisms may be considered as a primary or secondary factor in occurrence of the disease.

Possible effects of varying densities of cultured red algae Gracilaria corticata on algal growth parameters were studied using three density treatments 500, 1000 and 2000g/m2 in nine culture tanks. We conducted the experiment in April to June 2002 and carried out daily tests of salinity, pH and temperature which were in the range 37-40ppm, 0.5-8.04 and 23-32 degrees centigrade. Epiphytes such as Nitzschia, Navicula and Hypnea and grazers such as Amphipoda, Isopoda and Nereis were detected in the tanks during the experiment.We observed the highest daily growth and net production in treatment one (500g/m2) to be 3.74±0.31and 38.3±5.4 respectively and the lowest measurements were seen in treatment three (2000g/m2) recorded as 3.74±0.31and 38.3±5.4 respectively. Daily growth measurements were significantly different among treatments (P<0.05). Net production was significantly different between treatment one as a group and other two treatments (P<0.05). This was not the case between treatments two and three.

Four genera of phytoplankton including Tetraselmis, Chaetoceros, Skeletonema and Cholorella were used as food for protozoa stages of Penaeus semisulcatus in 10 treatmeants each with three replications of singular and double diets. In singular diet consisted of 40,000 cells/ml of Skeletonema, we recorded a survival rate 82%, growth rate 3.55 mm and period of development stage (Z I-MI) 92h which were higher than other treatments. In double diet comprised of Chaetoceros and Tetraselmis, the survival rate in 21 stage was 97%, higher than other treatments while in 22 and 23 stages, the highest survival rate was 95%, achieved by a double diet consisted of Skeletonema and Chaetoceros. In the latter diet, the growth rate and period of development for ZI-Ml stages were 4.58mm and 72h respectively. According to the results, we conclude that the survival and growth rates in singular diets are higher than double diets of the phytoplankton species.

We investigated the possible effects of light regimes on growth and survival rate of juvenile shrimp Penaeus semisulcatus cultured in Bushehr Province, southern Iran. Five light regimes each with three replications were applied for 30 days. The treatments were 24/0, 18/6, 12/12, 6/18 and 0/24 hours of light and darkness.We found that the treatment 12 / 12 hours of light and darkness was better than 18 / 6 and significantly superior to other treatments (P<0.05). The lowest growth rate was seen in the treatment 24 / 0 (P<0.001). We did not find a significant difference in the survival rate of the shrimps cultured in the light and darkness treatments (P<0.05).

In an 8-week feeding trial, attractants betaine, methionine and a mixture of betaine and methionine were added to diet of juvenile beluga (Huso huso) at different levels to assess their effects on growth and survival rate of the fish. In the trial, carried out in Shahid Marjani center for sturgeon hatchery and cultivation in Golestan Province of Iran, three different dietary levels 0.5%, 1% and 1.5% of attractants were used in PVC tanks filled with about 350 liters of water. We stocked 20 juvenile belugas with an average weight 28.2±2.63 grams in the tanks and fed them with four daily meals. Growth and survival factors were analyzed at the end of the trial period which showed that the addition of attractants in diets led to improvement of body weight gain, weight gain percentage, specific growth rate (SGR), protein efficiency ratio (PER), net protein utilization (NPU), condition factor (CF), survival, price index (PI) compared to control. The addition also led to a decrease in food conversion ratio (FCR) compared to control. The best improvement in indices was achieved with a diet enriched with 0.5% betaine and 1% methionine.

Water pollution due to chemical substances such as anionic detergents causes different disorders in aquatic animals. We studied the effects of anionic detergents on biochemical parameters of gold fish using 152 fish (18-20cm) which were divided into four groups. Group one was used as control and the other three were exposed to 5, 10 and 15 ppm of anionic detergents for 21 days respectively. Sampling of the fish serum was conducted on day 21 and the levels of urea, uric acid, creatinin, AST, ALT and phosphorous were determined. An ANOVA with multiple-range Duncan test were used for data analysis. Urea levels were significantly lower in test groups 1 and 2 and uric acid level was significantly higher in group 2 compared to those of the control (P<0.05). Creatinin level of group 3 and phosphorous level of groups 2 and 3 were significantly higher than those of the control (P<0.05). AST level was significantly lower in group 2 compared to control (P<0.05). As for ALT level in groups 1, 2 and 3, tests showed a significantly lower level compared to those of the control group (P<0.05).

The spawning season, fecundity and Lm50% of the Caspian Sea prawn (Palaemon adspersus) were investigated in the coastal waters of Guilan province. A monthly sampling was conducted using a bottom trawl with mesh size 3 mm in cod end in areas 0-5 and 5-10 meters deep during the year 2002.Mean total length, carapace length and weight of ovigerous female of Palaemon adspersus were 51.95±3.1mm, 13.95±1.9 mm and 2.742±0.58g (X±S.D). Minimum and maximum total length of ovigerous specimens were 37 and 59.3mm with a weight 1.002 and 4.145 grams respectively. We found that the spawning season of Palaemon adspersus begins in April and ends in September with a peak in June. Mean fecundity of the species was 1994.5±506.6. The size at which 50% of females are mature was estimated to be 51.27mm total length.

Bazangan, the Khorasan largest natural lake, is located in Northeast, 120km from Mashhad with the area of 690000 m2. The purpose of this study was to characterize ecological aspects and to compare seasonal variations in species diversity of phytoplanktons in the surface water of littoral zone in the Bazangan lake. Samples were collected from eleven stations in each season during the year 2002. Some ecological factors such as pH, EC, salinity, hardness of water, nutrients and water temperature were measured. Four macroalgae and 33 phytoplankton species belonging to 5 algae groups viz. Chrysophyta (21 species), Chlorophyta (7 species), Cyanophyta (4 species) and Pyrrophyta (4 species) were identified. Diatoma tenuis, Fragillaria crotonensis, Ulothrix subtilissima and Merismopodia punctata had the most species abundance. Comparing to other groups, Chrysophyta was abundant in all seasons mostly in the spring and summer. Different numerical indices of diversity such as species richness, evenness and diversity as well as parametric families of diversity were obtained in different seasons based on the abundance data of phytoplanktons. The results showed that the highest species diversity of the phytoplanktons could be seen in the summer and autumn. The Bazangan is classified as an oligothroph and a subsaline lake.

We studied genetic difference and resemblance between Acipenser persicus and Acipenser guldenstaedtii using Random Amplified Polymorphic DNA (RAPD) technique. The DNA of tail fin tissue of three A. persicus and A. gueldenstaedtii were extracted using phenol-chloroform method. After electrophoresis of the samples by agarose gel, their concentrations were regulated and Polymerase Chain Reaction (PCR) was conducted by 53 primers. PCR products were electrophoresed on polyacrylamide gel and silver staining was done to reveal the DNA bands of the samples.Among 53 primers, 17 had no site on genomic DNA of A. persicus and A. gueldenstaedtii and did not produce any bands while the remaining 36 primers showed band pattern. Analyzing the PCR products data using RAPD PLOT program showed that the maximum and minimum genetic distance between species were 73% and 65% respettively. Also, the mean-difference between the species was 70% and the maximum and minimum genetic resemblance between the two species were 35% and 27% respectively. Based on the results, we conclude that A. persicus is an independent species from A. gueldenstaedtii.

Presently the crayfish fishermen in Arass water reservoir use only Funnel traps. This study was conducted in 2002, to aimed for evaluating the ability of catch, sex ratio and the size frequency of crayfish with the Opera House traps and Funnel traps. Forty Funnel traps including and forty Opera House traps have been set in 7.5 and 10m depth from May to July (in each depth combination of 20 number of the two type traps). The linking rope also the stone being used to stream line traps in the bottom of lake. The results revealed no significant differences (P≥0.01) between the average length and weight of the crayfish caught with the two types of trap in different months of the year. The CPUE with Opera House traps was greater than with Funnel traps and the number caught in 24 h in one trap of the former type was 2.26 number higher, which was significantly higher than Funnel traps. A greater quantity of male crayfish was caught with Opera House traps, but compared with Funnel traps in respect of male crayfish catch, the difference was not significant (P≥0.05). Crayfish more than 120mm length (minimum standard size for commercial Arass crayfish) in Opera House traps comprised 87.56% of the catch, while by Funnel traps, the figure was 69.90%.Considering these finding, it is proposed that the crayfish fisherman in Arass be allowed to use Opera House traps, because they are more likely to improve crayfish population sustainability.

Cytochrome P4501A1 is a major isoenzyme in fish monooxygenase system which is induced by polycyclic aromatic hydrocarbons (PAHs) compounds. In this research, the inducing effect of p-naphtoflavone and its catalytic properties was studied in Huso huso liver. Fish were given ip injection of p-naphthoflavone at three different doses. The enzyme activity was measured with de-ethylation of ethoxyresorufin reaction (ERGO) by flourometery method and relative amount of induced proteins were determined using polyacrylamid gel electrophoresis (SDS-PAGE).The results showed that EROD activity in the microsomal fraction of the treated fish was 15-26 folds that of the control group. Optimum activity of this enzyme was observed at 20-25 degrees centigrade. The maximum enzyme activity was seen in the precence of 180 micrograms of microsomal protein and 1.53µM of 7-ethoxyresorufin. SDS-PAGE of microsomal protein pattern in the treated fish revealed a protein with molecular mass 58±1 KDa translating to cytochrome P4501A. We conclude that the p-naphtoflovone in fish liver can induce cytochrome P450lA gene and increase its biosemhysis leading to raised enzyme activity in EROD reaction.

We devised a device for precise fish egg counting that incorporated three units electronic, mechanical and water network. In the device, a selector disc (mechanical unit) separates each egg from the batch and injects it into a fluid stream (water network) which is then detected by an inferared interrogator. The electronic detector generates a pulse to counter circuit and then activate the numerical, display showing the number of the past eggs. There is also the option of a present system that allows programming number of the eggs that should be counted. The machine will stop when this preset number is reached. The efficiency of all parts were examind with trout eggs with an average diameter of 4 to 5.7mm. In the fish trial, we obtained an undercounting of 16 eggs. After adjustments, the undercounting reached unity.The selector disc was designed in the sizes of 4.5, 5.5 and 6.5mm to allow counting of most egg sizes. The first disc size allowed counting of 9000 eggs per hour. The counting capability increasd to 30,000 eggs per hour when more holes were punched in the disc. It is possible to increase the counting rate using higher velocity of disc rotation, mounting double discs or two dtectors with one disc.

Knowledge of nutritional requirements and especially protein levels is needed to produce strong and larger freshwater crayfish in controlled conditions. This has not been available for the miniature size crayfish culture. Hence, an eight-week experiment was conducted on miniature size crayfish in three treatment groups each with three replicates receiving a diet that contained 25%, 30 % and 35% protein levels with isocaloric digestible energy (DE) 3500 kcal/kg. A number of 540 miniature crayfish with a mean weight 100±12mg were randomly selected and partitioned into nine tanks containing 200 liters of freshwater70% of which exchanged daily. The fish were fed at 25% of body weight five times daily at 6, 10, 14, 18 and 22 hours using pellets 0.1, 0.2 and 0.4 mm. Nutritional responses in term of weigh gain, PGR, FCR, FCE and PER were compared among the groups using one-way ANOVA. The test showed a significant increase in the indices such as WG and PER in response to increased protein level (P<0.05).FCR, FCE and PGR show a significant increase using 20% protein level while using 30 and 35% protein levels did not produce significant results (P<0.05). The test revealed a significant difference between treatments 1 and 3 (P<0.05) but not between 1 and 2. I conclude that the treatment 3 produces more reliable results.

We used PCR-RFLP method to identify cuttlefish (Sepia pharaonis) populations in the Persian Gulf and the Sea of Oman. Bottom trawling method was used to collect a range of 20 to 40 specimens from each 15 stations in the study area. Genomic DNA was extracted by phenol-chloroform method and one pair primer was designed for the analysis based on 18s rRNA gene nucleotide sequences. A PCR product with 502 pair bases in length was obtained for all specimens and subjected to digestion by eight restriction enzymes AluI,TaqI, MnlI, RsaI, HindIII, DraI, PvuII and HaeIII. DNA banding patterns in all specimens were similar and no polymorphism was detected among them. We conclude that cuttlefish populations cannot be isolated using 18s rRNA gene extracts in the area of study.