فصلنامه شیلات
سال شصت و پنجم شماره 2 (تابستان 1391)

Artemia plays a major role in aquaculture as one of the most important live foods used in larval rearing. The aim of this study was to determine the optimum level of feeding in Artemia urmiana with Baker's yeast (Saccharomyces cerevisiae). Triplicate groups were fed with different levels of S. cerevisiae yeast 0.625 (control), 1.25 (T1), 2.50 (T2), 5.0 (T3) (mg yeast per 1000 nauplii) for 10 days. Culture conditions such as temperature (29oC), Dissolved oxygen (5 mg/l), Salinity (60 g/l) and pH (8) were set according to Standard Method. At the end of the trial, total length, dry weight, survival rate and biomass production were measured. Moreover, average daily growth (ADG), body weight increase (BWI), specific growth rate (SGR) and condition factor (CF) were determined. The results showed that total length (2.10±0.14 mm), dry weight (11.75±1.91µg), biomass production (129.55±21.3 mg/l) and survival rate (62.2±12.2 %) of T2 were significantly higher than. Also ADG (1.12±0.19 mg), BWI (11.21±1.89) and SGR (30.71±1.41) were significantly higher in T2 compared to other treatments. The highest CF was observed in T4 (60.47±21.46) and the lowest was observed in T2 (22.89±3.01) (P<0.05). According to these results, the best level of Artemia feeding with S. cerevisiae was 1.25 mg of S. cerevisiae per 1000 Artemia nauplii. Also our results indicated that food efficiency depends on the amount of food available, and it was increased with food availability to a certain level.

Effects of different nutritional conditions on iono-osmoregulation in juvenile of Caspian trout (Salmo trutta caspius) parrs were studied. Following adaption to the new environment, 750 Caspian trout parrs (12.5±1 g) were kept under the treatments of six weeks of full feedings (FFF), three weeks of feeding-three weeks of starvation (FS), six weeks of starvation (SSS), two weeks of feeding-two weeks of starvation-two weeks of re-feeding (FSF) and three weeks of starvation-three weeks of re-feeding (SF). Fish were fed with rainbow trout commercial feed three times a day up to satiation. There was no significant difference in serum sodium, chloride, potassium and magnesium between treatments, but serum osmolality decreased from 299 mOsmolkg-1 in FFF to 286 and 271 mOsmolkg-1 in FS and SSS (P <0.05), and re-feeding, after starvation periods, compensated the osmolality reduction to the similar levels in FFF. Five days after transferring the parrs to Caspian Sea (salinity: 13 gL-1), serum magnesium reached to 3.55 and 3.40 mEqL-1 in FS and SSS respectively (P <0.05), in comparison to FFF group (2.36 mEqL-1). Serum potassium showed also irregular significant difference between treatments (P <0.05), while chloride and sodium presented no significant difference. Serum osmolality levels increased to a maximum of 415 mOsmolkg-1 in FS and were decreased to a minimum of 306 mOsmolkg-1 in SSS (P<0.05), compare to FFF (366 mOsmolkg-1). We concluded that starvation has negative effects on ion regulatory capacity of Caspian trout parrs and although re-feeding can increase this capacity but effects of long period starvation cannot be compensated.

Diazinon is commonly used for pest control in the agricultural farms surrounding freshwater reservoirs. Therefore, this study was conducted to determine the sub-lethal toxicity of this organophosphorous pesticide, in aquatic ecosystems as a pollutant, and its effects on histopathology of liver and some biochemical blood parameters of common carp, Cyprinus carpio. Diazinon was applied at sub-lethal concentrations of 60 and 120 µg/L during 10, 20 and 30 days. Compared to the control specimens, fish after a chronic exposure to diazinon had significantly (p<0.05) higher plasma Aspartat transaminase (AST), Alanin transaminase (ALT), alkaline phosphatase (ALP), lactate dehyrogenase (LDH), cretinin phosphokinase (CK) activities, and levels of glucose, albumin and cholesterol, but no significantly differences in total protein and globulin levels were observed between treated fish and control group. The histhopathological effects of diazinon on liver tissue of C.carpio, were examined by light microscopy. Disorientation of liver cells, cytoplasmic and nuclear material deposition, vacuoles formation in liver tissue, liver cell necrosis and destruction of the structure and rupture of the blood sinuses were observed in the liver tissue of treated fish by diazinon.

Some hematological indices and plasma biochemical parameters were determined in two Capoeta; C.trutta and C.damascina from Gheshlagh Dam Lake, Sanandaj based on seasonal changes and thier age and gender dependent.There was no gender dependent significant difference in hematological indices of both species. Comparsion of indices between the two studied species showed that neutrophil and monocyte percentages, erythrocyte count, hematocrit, hemoglobin concentration, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration were significantly higher in C.damascina however, the percentage of lymphocyte was higher in C.trutta than C.damascina. Total leukocyte count, monocyte percentage and plasma total protein of C.trutta were significantly different among 2-4 years old classes, however there was no significant difference between indices of C.damascina for the same age groups. The effect of season on blood indices of C.damascina showed that the highest total leukocyte count and plasma phosphorus concentration were attained in summer, while the highest values for monocyte percentage and hematocrit were observed during winter. Erythrocyte count and hematocrit of C. trutta were raised in winter and mean corpuscular hemoglobin was decreased in this season. The study has provided baseline haematological and some biochemical data of C.damascina and C.trutta which could be used in health monitoring and future comparative surveys of these species.

This study examined the effects of implanted cortisol (to imitate chronic stress) on the hematological responses and cortisol values of female great sturgeon, Huso huso, after an endoscopic operation. At the beginning of experiment, all the fish were examined using an endoscope to evaluate gonad development. Then, in order to mimic chronic stress following surgery, capsules of cocoa?? butter containing cortisol were intraperitoneally implanted to 3-year-old female fish in reproductive II stage (mean body weight 6759 ± 53.23 g). The implant doses were 0 (C0; as control), 5 (C5) and 50 mg cortisol /kg BW and there were five fish per treatment group. Blood samples were taken every week during the 28 days of the experiment to evaluate hematological responses and blood cortisol concentration. There were no significant changes in serum cortisol in C50 group during the experimental period, but an upward and significant trend in serum cortisol was observed in C5 group. Also, cortisol levels in C5 group were significantly higher than those of the control and C50 groups from second week after endoscopic surgery and implantation onwards. White blood cells increased after endoscopic procedure, but the response was lower in control fish than those receiving cortisol. Hemoglobin and hematocrit did not change with treatment or time. Significant differences were observed in the percentage of lymphocyte and neutrophil cells in the second and fourth weeks after implantation, so that lymphopenia and neutrophilia were observed following cortisol implantation. The present study revealed that exposing fish to chronic stressors after an endoscopic operation decreased the immune response and had an immunosuppressive effect. Also, these results suggest that great sturgeon exhibit a low response to slow release of cortisol compared to teleostean fishes.

Fish finger is a semi-prepared product of fish that many studies have been done to improve its texture, taste, flavor and color. The present study aims at investigating the quality and sensory characteristics of fish fingers produced from fillet and surimi of common carp during storage in refrigerator. Fish fingers were packed and then stored in refrigerator (4 °C). Chemical parameters (fat content, heme iron, peroxide value (PV), Thiobarbituric Acid (TBA), total volatile baseic nitrogen (TVB-N) were measured and sensory analysis (texture, smell, taste, color and total acceptance) were determined by panelists on 0, 3, 6 and 9 days. The amount of peroxide (meq o2 /kg fat fish), thiobarbituric acid (mg malondialdehyde/kg fish flesh) and total volatile bases nitrogen (mg N/100 g fish flesh) of fish fingers between treatments were significantly different (P< 0.05). While the values of fillet and surimi fish finger reached to 4.07, 0.9, 33.17 and 3.53, 0.77 and 13.73 at the end of storage, respectively. The increase of values in fillet fish fingers was more than surimi fish fingers (P< 0.05). Heme iron content in both treatments showed a significant decrease. Total fat of fillet fish finger showed a significant decrease in comparison to surimi at the end of storage. Results of sensory analysis indicated significant reduction in sensory characteristics of fish fingers. Based on sensory analysis of two different types of common carp fish fingers shelf life was determined six days in refrigerator.

Mycosporines are UV-absorbing metabolites which are produced via aromatic amino acids synthesis pathway (shikimate pathway). In the present study the effect of diet was examined on accumulation of these compounds in Artemia urmiana and parthenogenetic Artemia. The cysts of both strains were hatched under standard conditions. The larvae (instar-I nauplii) were directly transferred to the diluted Urmia Lake water (150 g l-1), the salinity was then increased gradually up to 250 g l-1. During the culture period, both Artemia strains were fed on two algal feeding regimes including green and red Dunaliella salina. Concentration of seven Mycosporines including Asterina-330, Shinorine, Mycosporine-2Glycine, Palythine, Porphyra-334, Mycosporine-Glycine:valine and Palythinol were measured in adult Artemia using HPLC at the end of experiment. Results showed significant increase in the concentration of mycosporines in both Artemia populations fed on red algae compared to those received green algae, except for Shinorine in A.urmiana. Parthenogenetic Artemia showed higher capability for accumulation of Mycosporines compared to A. urmiana in most cases.

The intensive use of antimicrobial agents worldwide for prophylactic and therapeutic purposes has been associated with increase of bacterial resistance in the exposed microbial environment. Oxytetracycline is the most frequently used antibacterial in the cold water fish industry because of its broad spectrum of activity and low cost. Aeromonas hydrophila and other motile aeromonads are among the most common bacteria in freshwater habitats throughout the world, and these bacteria frequently cause disease among cultured fishes. In this study, 50% of isolates from intestine of rainbow trout were identified as Aeromonas hydrophila by using biochemical technique. Oxytetracycline MICs were determined using agar dilution method at dosage 0,1,2,4,8,10 µl/ml. 40% of Aeromonas hydrophila was resistant to 30 µg/ml of oxytetracycline. The use of oxytetracycline in aquaculture might produce some negative impact on the treatment of human infections as a consequence of either direct transmission of resistant pathogens to humans, or indirectly through the transfer of resistance genes from environmental bacteria to human pathogens which is major risk for public health.

The present research aimed to study the growth and reproductive parameters of common Kilka Clupeonella caspia in southern Caspian Sea in 2010. After measuring the length and weight of 3774 samples, they were dissected, sex determined and female gonads were weighed. Sexual maturity classification was carried out based on six stages. Age was determined using sagitta otoliths. Length-weight relationship was (R2=0.918). Growth parameters were (L∞=128.7mm, k=0.41yr-1, t0=-0.59yr). Age composition was constituted of 6 age groups, including 1-6 years. Age average was 3.27±0.09 years. 3 years old fish were the largest age group, composing 45.24% of the catch population. Male: female ratio was 1: 0.779 and males were dominant. Study of sexual maturity stages and GSI showed that common Kilka spawning begins in February and the peak was in May and June. Survival rate was 0.239 yr-1. Natural and fishing mortality coefficients were 0.448 yr-1 and 0.983 yr-1. The exploitation rate calculated up to 0.687 indicating the species over fishing. Our results showed that the mean length and weight of common Kilka population has increased but the mean age decreased during the last years.

This study was conducted to evaluate the effect of different lecithin sources and their levels on growth performance and resistance to anoxia stress of rainbow trout (Oncorhynchus mykiss) alevin with initial weight of 120 ± 4.08 g for 40 days. Soybean and egg lecithin at 2, 4 and 6 ℅ levels were added to the diets. Seven treatments by three replications were used in this experiment. Therefore, 165 alevin were used per each 90 L tank. Alevin were fed to visual satiation at six meals per day for 40 days. At the end of experiment, alevins were fed by 2℅ egg lecithin had significantly higher (p<0.05) growth performance compared to control group. Growth parameters in soybean lecithin groups were not significantly different compared to control group. Alevins were fed by 6 ℅ egg lecithin had significantly higher survival rate than other treatments and control group. Also alevins were fed by all levels of egg lecithin had significantly higher resistance to anoxia stress compared to control group. The result of this experiment showed that egg lecithin induced to significantly affect on the growth performance and resistance to anoxia stress. The optimal dietary level of egg lecithin for this size is 2 ℅ of diet.