Iranian Scientific Fisheries Journal
Year:2009 | Volume:17 | Issue:4|Papers Count:25

The marine rotifer Brachionus plicatilis is extensively used as a major live food in fish larvae culture all over the world. In the present study an attempt was made to find out the optimum salinity and feeding conditions for growth of the rotifer B. plicatilis. The rotifer was cultured using Batch culture method at four salinities ranges (20, 25, 30 and 35ppt) and was fed with 3 species of microalgae including, Nannochloropsis oculata, Isochrysis galbana and Chlorella sp. The difference between salinity was not significant (P>0.05) but there was a significant difference between the food types (P<0.05). In all of the experiments, the combined effect of salinity and algal type on rotifer growth were significant (P<0.05). The best result was observed in the experiment conducted at 35ppt salinity using N. oculata as the main food (378 ind/ml).

Samples were collected from 24 farmed Acipenser stellatus (7 years old) including 14 females and 10 males during summer 2005 to spring 2006 in the International Sturgeon Research Institute (Rasht, Iran). Testosterone levels showed significant different in males at the stage IV (P<0.05). Minimum rate of Testosterone was 9.21±5.7ng/ml in winter and its maximum was 556.3±45 ng/mlin spring, and 17a-hydroxy progesterone levels in males showed chaotic fluctuations in different seasons. 17b-estradiollevels in males and females at the stage IV showed significance difference in various seasons (P<0.05) and in males it was at its minimum (1.36±1.3ng/ml) in spring and its maximum (4.4±1.2ng/ml) and in females it was minimum (2.65±84ng/ml) in spring and maximum (31.5±8.6ng/ml) in autumn. We found no significant differences in male and female hormones levels at the stages II, III and III-IV in different seasons. Comparison of Testosterone and 17a-hydroxy progesterone in males and females showed that Testosterone level was more than progesterone at similar conditions. Based on the results, sex steroid hormones, Testosterone, 17a-hydroxy progesterone and 17b-estradiol hormones are the three most important indices of sexual maturation that could be used for sex identification of the sturgeons at rearing conditions.

Persian sturgeon, Acipenser persicus is a valuable species in the Caspian Sea ecosystem. For gill chloride cells localization, fish specimens 2-3g were adapted to experimental conditions for 7 days. Gill histology was observed through light microscopy using Hematoxylin-Fushin staining. Immunolocalization of gill Na+, K+-ATPase was observed through fluorescent microscopy using mouse monoclonal antibody (IgGa5) rinsed against (Na+, K+-ATPase a-subunit. Chloride cells dimensions was observed using Image Tools software.Gill chloride cells that have high densityof Na+, K+-ATPase, were found on gill arch, gill septum, filament and lamellae. No chloride cells were observed on spiracular or opercular gills epithelium. Chloride cells were spherical to egg-shaped and showed immunefluorescent activity on their baso-Iateral sides. Results showed that in each square millimeter of gill epithelia, 289 chloride cells existed and the maximum number of these cells was found on filament, lamellae, base of the lamellae and on the inter-lamellar space. We also found that the number of these cells is significantly different in all branchial states. Persian sturgeon fry weighing 2-3g have gill chloride cells where Na+, K+-ATPase gene and their activity occurred. Because of their cellular transporters (like Na+, K+-ATPase), these cells were the main sites of the ionic and osmotic regulation between the fish and the environment.

Heavy metals concentration (Cd, Pb, Cu, Ni) in muscle and gill tissue of the fish Barbus grypus was assessed in winter 2007. In total, 60 fish samples were taken from Arvand River and experiments were carried out on two fish tissues (muscle and gill) separated after biometrical measurements. Extraction of the heavy metals was performed using concentrated nitric acid and then A.A.S. was used for measurement t of the heavy metals. Results showed 2.83, 16.42, 2.68, 0.77mg of heavy metals for gram dry weight of the fish for cadmium, lead, copper and nickel concentration in muscle tissue and 2.79, 9.03, 6.98, 1.39 in grill tissue. Metal levels in muscle tissue in this restack were compared with standards values such as World Health Organization (WHO), Ministry of Agriculture, Fisheries and Food (MAFF) and National Health and Medical Research Council (NHMRC), based on which only lead and cadmium showed higher than standard levels.We found positive linear relationship between metal accumulation levels of cadmium and lead in muscle and gill tissue with total length and weight. There was a significant relationship between copper accumulation level in muscle tissue with weight but not so for the length. There was no significant relationship between copper accumulations level in the gill tissue with length and weight. There was significant relationship between nickel accumulation levels in the gill tissue and the total length and weight but not so for the muscle tissue.

In a 30 day feeding trial, daphnia and Artemia extracts were added to diets of juvenile Beluga (Huso huso) at different levels to evaluate its effects on growth and survival rate of the fish. The trial was carried out in aquaculture research center of the Gorgan University, during which three different dietary levels of extracts (1:25, 1:50 and 1:100) were used in 250 liter PVC tanks filled with about 125 liters of water. A total of 20 juvenile Beluga with an average weight of 5±0.2 geach was stocked in tanks and were fed 4 meals a day. Growth and survival factors were analyzed at the end of the trial period. The results showed that the addition of extracts in diets led to improvement of body weight increase, weight increase percentage, specific growth rate (SGR), daily growth rate (DGR), daily growth index (DGI), condition factor (CF), price index (PI) and decrease of food conversion ratio (FCR) compared to the control treatment. The best improvement of growth index was achieved at the dietary level 1:50 Artemia extracts. There was no significant difference (P>0.05) in survival among treatments.

A total of 162 specimens of Silver Pomfret (Pampus argenteus) including 38 samples from Kuwait and 124 samples from Iran (24 from Khouzestan, 24 from Chabahar and 38 from Bushehr) were examined for their DNA structure. DNA from all specimens was extracted using the Phenol-chloroform and amplified using PCR method with a pair of primers with ND2 gene sequence. The PCR products were abowt 1300 (bp) for all samples. For RFLP analysis 16 restriction enzymes Bel I, Pst I, Acc II. BseN I, Tru I, Dra I, Alw26 I, Hin6 I, Tas I, Alu I, EeoR I ,Hae III, Hine II. Hind III. Hinf I and Hpa II were used. DNA bands were visualized by Gel electrophoresis (polyacrylamid) and staining with silver nitrate. Out of 16 enzymes, four showed polymorphism that includedg Hinf I, Alu I, Ace II, and Hpa II. Of the total 162 samples, 13 showed polymorphic patterns. Six haplotypes were rare occurring only once, but others which were only four different kinds occurred more than once. The REAP test gave no significant result for the examined regions (P>0.05). Therefore, our results revealed that the Pampus argenteus stocks in the Persian Gulf and Oman Sea of Iranian and Kuwaiti waters constitute a unique population.

The aims of the present study were to examine bioaccumulation of heavy metals copper, zinc, iron and manganese in rainbow trout eggs at different stages of incubation period and to compare the results with those of the EPA standards. The research was carried out at t Firoozkooh Namroud Rainbow Trout Hatchery Center. For this purpose, two incubators with the same condition as experimental units were selected, one of them was the experimental incubator with approximately 60000 eggs and the other one had no eggs as the control. Sampling of eggs and water during incubation period was conducted weekly. The results showed significant differences (P<0.05) and decrease in the concentration of the studied elements in the discharge water of the experimental incubator compared to the input water but this comparison did not show any significant differences (P>0.05) in the control incubator. This indicates that eggs have absorbed these elements from incubation water and then showed increasing trend for Zn and Fe elements concentration in dry weight egg extract during incubation stages but increasing trend in Mn and Cu elements went on until the third stage. The results indicate that threshold concentrations for Mn and Cu in egg cause egg resistance against more absorption of these elements. Also, the results showed that at all sampling stages, concentration of the studied elements was lower than EPA standards for animal textures.

The main fishing ground for shrimps in Hormozgan province along the Persian Gulf are located in the north of Qeshm Island to Sirik area with a yearly catch of 1500-2000 tons from east coast of Hormozgan province located in Iranian waters of Oman Sea.Collection of breeder shrimps in important fishing grounds of Sirik to Jask area was started in 1995 for shrimp culture objectives and the present research was carried out in 2001 to 2002 and 2007, aiming at identifying shrimp species, determining frequency distribution of the species in the catch and evaluating shrimp maturity stages in the catch. Samples were collected using swept area methgd on a biweekly or monthly basis. Result showed that Fenneropenaeus indicus was dominant in the shrimp catch comprising 44.8-59.5% while this rate was 13.5-34% for Fenneropenaeus merguiensis, 15.7-20.5% for Penaeus semisulcatus, 5.5-16% for Metapenaeus affinis, 0-14.5% for M.stebbingi 0-4.5% for Parapenaeopsis stylifera in the Jask and Sirik areas in 2001-2002 and 2007. CLM50%was 34.7mm for F. indicus females, 31mm for F. merguiensis, 34.3mm for P. misulcatus and 27.16mm for M affinnis in Jask and Sirik areas. Tukey test showed that the average carapace length in F. indicus, F. merguiensis and P. semisulcatus caught in Jask were significantly larger than those from Sirik area (P<0.05). Sex ratio was not 1:1 in these shrimp species and there is significant differences between them (P<0.05). Maximum abundance of F. indicus, F. semisulcatus, M.affninis and F. merguiensis spawners, were found during March to June in Jask and June to July in Sirik areas.

Experimental pathology of Streptococcus sp. was studied in Rainbow Trout weighing 18- 20 grams each using bath (1.5x103, 1.5x104, 1.5x105, 1.5x106, 1.5x107, 1.5x108 cell/ml for one hour) and intraperitoneal (1.5x103, 1.5x104 1.5x105, 1.5x106, 1.5x107, 1.5x108 cell/fish) challenges provided at 18°C. Control groups were included by intraperitoneal injection of fish with sterile phosphate buffered saline (0.5 ml/fish) after anesthetizing fish with clove oil (100 mg/l). Six groups consisting of 12 fish each were used. No morbidity or mortality occurred in bath-immersion groups, while mortality occurred in intraperitoneally injected fish 24 hours post-challenge and reached LDsoat 1.5x108 cell/fish 72 hours post-challenge. The affected fish showed anorexia, darkening of body, exophthalmia, and prolapsed anal abdominal distension. In his to-pathological sections, there were hyperemia and sinusoidal congestion plus necrosis and degeneration of liver hepatocytes. Also, hyperemia in heart tissue, an increase in interstitial tissue plus necrosis of kidney tubular, edema of Bowman capsules together with an increase in melanomacrophage centers of kidney tissues were seen. In addition, congestion of spleen ellipsoids and necrosis of spleen cells were observable. Detachment of basal membrane of secondary lamella with infiltration of inflammatory cells, congestion and edema of menangial layers, hemorrhage in orbital adipose tissue and destruction of eye cornea were also observable.

Extraction of omega-3 fatty acids from Kilka fish oil was conducted at the laboratory scale. Extraction and purification of raw and refined Kilka oil were done in three temperatures (1,-5 and -10°C) using urea complex method.The results indicated that maximum extraction of fatty acids were achieved at 1°C and during the experiment, omega-3 ratio was increased while the saturated fatty acid and long chain menstruated fatty acids were decreased. The mean value of omega-3 acids for the refined and raw fish oil was 29.28% and 26.05% respectively. The extraction and purification t increased omega-3 fatty acids in the refined and raw fish oil to 79.8% and 68.9% respectively. Moreover, the maximum rate of pure fatty acids was also 80.51% and 69.29%. The statistical analysis showed that omega-3 ratio before and after extraction as well as purification, were significantly different (P<0.04 for raw and P<0.03 for refined fish oil). In conclusion, we can say that the fatty acids purification by urea complex was fully successful and it has the potential to be used in fish oil extraction pilot plants.

Sampling and determination of seaweed biomass was carried out in the Oman Sea coasts along the intertidal waters of Sistan & Baluchistan province stretching 300Km from Guater area to Jood from October 2001 to September 2002. The regions covered included Guater, Passabandar, Beris, Kachoo, Ramin, Chabahar, Pozm, Gurdim, Tang, and Jood as sampling stations from east to west. The intertidal zone was determined by measuring and recording of geographical positions by GPS. Fifteen transects were aligned randomly each month with equal distance to the coast. All sampling attempts were mad, eby applying quadrats 50x50cm in dimension. The samples were transferred to the lab and the weight of each species was measured after being cleaned, and identified. The biomass of each species per unit area and in the total area was obtained after determining the average weight of species. During the research, 69 species were collected, of which, 16 species were green algae, 18 species were brown algae and 35 species were red algae. There were some important families including green algae (Ulvaceae & Caulerpaceae), brown algae (Sargassaceae & Dictyotaceae) and red algae (Gracilariaceae, Gelidiaceae and Hypneaceae). Wet biomass of seaweeds in the total area of Sistan & Baluchestan coasts was 10286340.3 kg of which 2645192.1kg (25.7%) were green algae, 2955963.9kg (28.7%) were brown algae and 4685184.2 kg (45.5%) were red algae. The estimated monthly average was 264522.3, 295327.9 and 467089.7Kg for green, brown and red algae respectively. The maximum biomass was 15.4kg/m2 seen in Chabahar and the minimum biomass was 4.9kg/m2 obtained in Pozm.

The Persian Gulf fisheries are currently managed through regulations that restrict access to the fishery. These controls do not overcome the incentive for over fishing that follows from lack of ownership in open access fisheries. In such situations, more effort is required to maintain fishery resources.ITQ system of fisheries management is increasingly recognized as a practical alternative to traditional regulation methods. Traditional administration of fisheries as a common property has failed to ensure the fishery resource management is a sustainable way. Worldwide, fishery management systems are now turning to sustainable utilization of the fishery resources. ITQ's are part of this transition.Shrimp fishermen's opinion on the current shrimp management system and the possible change to a new ITQ system is examined in this study. We used a questionnaire and a stratified random sampling method, through which a total of 144 fishermen were interviewed in Hormozgan province. Descriptive statistics and contingency tables were used to estimate the agreement of fishermen with ITQ system in the study area.The results indicated that most of the fishermen do not agree with the change in the shrimp management system. Despite this result, the interviews showed that the younger, more experienced, highly educated and lower income fishermen mostly agree with the change in the current management system compared to other groups. Although the overall result does not endorse the move towards using ITQ system, but we believe that the ITQ system provides a new management system that efficiently reduces current problems.

Caspian salmon (Salmo trutta caspius) juveniles were fed with dietary nucleotide levels of 0, 0.15, 0.25, 0.35 and 0.5% to investigate their effects on growth performance, survival rate and liver enzymes. Juveniles with an initial average weight of 12.26±0.001g were fed with the experimental diets for 60 days. The trial was carried out in 300 liter tanks each containing 35 fish which were fed with five meals a day at the rate of 3-5% of body weight. Statistical analysis was performed using One-way ANOYA.Results of the study showed that the addition of dietary nucleotide led to significant increase of body weight gain (BW), weight increase percentage (BWI), specific growth rate (SGR), protein efficiency ratio (PER), protein productive value (PPY) and feed intake but significant decrease of food conversion ratio (FCR) as compared to the control treatment (P<0.05). No significant difference was found in condition factor (CF) and survival rate among the treatments (P>0.05). The best value of growth improvement indices was observed at the dietary level of 0.25% nucleotide. Liver enzymes including AST, ALT and LDH at the level of 0.35% and ALP at the level of 0.25% were significantly lower than control treatment (P<0.05). Our results also indicated that dietary nucleotide can have positive effects on growth performance and would decrease liver demolition.

This survey is part of the investigation on feasibility of introduction of Litopenaeus vannamei Boone, 1931 in shrimp culture industry of Iran. The objective was evaluation of the adaptation of the white leg shrimp, L. vannamei to brackish ground waters of the Bafgh area in Yazd province. Around 120000 shrimp postlarvae (PL7 & 15) were stocked in four 0.15ha earthen ponds (17 & 23 ind/m2) in July 2005 and the culture period took about four months. Physicochemical and biological factors were studied during the culture. Shrimps were fed with commercial feed of the L.vannamei. Results showed low survival (19.2%) and growth (2-2.5g mean body weight). Based on the assessments, the limnological factors were most unfavorable elements causing the low growth in the shrimp. Concentration of K, Ca, Mg and Na Fe (II & III), different heavy metals, nitrogenous compounds, water hardness and the season and thermal periods are probably the most essential factors affecting production yield of the shrimp because of underground origin of the water. Also, the structure of ponds and drainages, presence of invasive water plants and insects may have affected the survival and growth of the shrimp as well.

We studied the morphological characteristics of the Caspian Lamprey (Caspiomyzon wagneri) in two rivers of Shirud and Talar during the spring migration in 2006. A total of 91 specimens were collected using hand and cast net. Relative morphometric characters including disc length, head depth, eye length, prebranchial length, head length, distance between disc and posterior end of the first dorsal fin, distance between disc and base of second dorsal fin, distance between disc and anus, post branchial length, tail length, interocular distance, and post ocular length showed significant differences between the two populations (P£0.05), but meristic characters showed no significant differences (P³0.05). Although some of the relative morphometric characters showed differences between the two populations of the rivers, but the populations were not different based on the principal components analysis (PCA) and had a relatively high overlap.

Otoliths or ear stones are small white bodies present in the ear of bony fishes. Otoliths are important in keeping fish position and steadiness and also are useful structures in hearing. There are three pairs of otoliths which are called Sagittus, Lapillus and Astriscus. In the present study, otoliths of 15 species belonging to 14 genera and 6 families were collected from different basins including Kor Watershed, (Ghadamgah), Persian Gulf (Ghara Aghaj River), Hormuz (Khurgu Hot Spring), Tigris and Karon (Ghaghakhor wetland) and also some fish farms of Fars province were examined. Results showed that in Salmonidae, Cichlidae and Cyprinodontidae families Sagittus is larger while in the Balitoridae, Cobitidae and Cyprinidae Asteriscus is bigger than the other otoliths. Moreover, there is high variation in Asteriscus shape in different families.

In this study, spatial distribution of the invasive ctenophore Mnemiopsis leidyi in the littoral waters of the Caspian Sea was evaluated using data collected at stations during the spring 2002 cruise. The average and maximum biomass of M.leidyi were 21.38 and 108.42gwet weight per m2, respectively. The average biomass of M.leidyi was 32.6g wet weight per m2 in the Iranian coastal waters whereas it was 24.99, 9.83 and 0.9g met weight per m2 in Azerbaijan, Turkmenistan, and Russia respectively. The maximum size of the ctenophore was 16-20mm, and the bulk of individuals (97.2%) were smaller than 10mmin length.