نشریه پژوهش های ماهی شناسی کاربردی
سال دهم شماره 4 (زمستان 1401)

Standing biomass of coral fish was estimated by the Underwater Visual Census method(UVCm) and belt transect in five stations (St.) (dead corals, continuous and developed reefs, discrete and undeveloped reefs, Acropora spp. in small amounts and rocky reefs), in Larak Island from Sep.2020 to Apr.2021seasonally.The maximum and minimum of standing biomass was estimated  908.79 (Kg/Km2) and 235.85 (Kg/Km2) in the Abbas St. and Arabha St. respectively, also the maximum of coral fish standing biomass belonged to Scarus ghobban with 703.99 (Kg/Km2). The maximum of average (standard deviation) was estimated for the Jetty St.(Kg/Km2)16.36(± 4.3) (Feb.2021), and the lowest value at Ghail St. 1.4 (± 1.96) (Kg/Km2)(Sep.2020), also confidence interval of these estimations from bootstrapping simulations (n=2000) was calculated(95%). The results of one-way analysis of variance, Tukey's test, comparing the standing biomass of coral-fish (temporal and spatial analyses), was concluded differences in the most of seasons and stations (P<0.05), and the highest of standing biomass belongs to cold seasons of the year(Oct.2020, Feb.2021) and the lowest of them in the warm seasons(Sep.2020, Apr.2021) is estimated. The study of coral fishes showed although the bleaching event in the Persian Gulf has destroyed the habitat of coral fishes, but the dead corals are covered with microalgae, rocks, developed reefs and a few colonies of living corals (Acropora spp.) at depths above 10 meters have been able to play the role of their habitat. Furthermore, the type of substrate cover, the integrity of evolution reefs, being sheltered from waves and winds, and being away from sources of stress have influenced more than the size of the habitat on the coral-fish stocks of the Hengam Island.

In this study, the catch composition and the catch per unit effort (CPUE) of sturgeon spawners caught by the gill net were investigated in the fishing grounds of Mazandaran province in two regions 3 and. Sampling and data collection of sturgeon spawning fish was done seasonally from 7 fishing grounds using gill nets with a mesh size of 150 mm. The results of the Chi-square test showed that there was a significant relationship between the time and place of Caught Persian sturgeon and Starry sturgeon (P<0.05) There was a significant relationship between the time and place of fishing with the abundance of fish spawners caught between regions 3 and 5 with spring and autumn seasons (P<0.05). There was a significant relationship between the time and place of fishing with the abundance of Starry sturgeon spawners caught between regions 3 and 5 only in the winter season (P<0.05). Also, a significant difference was observed between the amount of catch per unit effort of the spawning fishes caught in regions 3 and 5 (P<0.05) and between the averages of the catch per unit effort of the spawning fishes caught in the spring and summer seasons. Also, there was a significant difference between autumn and winter (P<0.05). Since the spawners of the caught sturgeon belonging to the Starry sturgeon and Persian sturgeon had the highest number compared to other species, so the results show the influence of the spatio-temporal factors of the habitats on their spawners.

The lakes behind the dam considered as semi-natural resources and have a special role in aquaculture. In order to achieve management goals, it is necessary to know the pattern of changes in biotic and abiotic parameters in the lake behind the dam. For this purpose, in order to determine water quality using water quality indicators (WQI) 12 physicochemical properties (water temperature, dissolved oxygen, salinity, acidity, electrical conductivity, suspended solids, total hardness, total alkalinity, nitrate, ammonia, phosphate and phosphorus Total) was evaluated in 2018 on a monthly basis for one year at 7 stations of Golestan dam in Gonbad city. Although temporal and spatial changes observed in some measured factors; According to the WQI index in Golestan Dam, it was relatively average to good in different months. Therefore, it evaluated as favorable for the breeding of tropical and subtropical fish.

Determining the optimal culture density is necessary to improve fish performance and profitability. A total of 1350 rainbow trout with an average initial weight of 30±1.5 g were obtained. Then, the fish were randomly distributed in 12 fiberglass tanks and reared at densities of 15, 30, 45 and 60 kg/m3 for 60 days. The final weight, weight gain, and protein efficiency ratio were significantly higher and the feed conversion ratio was lower in fish reared in densities of 30 and 45 kg compared to densities of 15 and 60 kg. The highest levels of serum cortisol and lactate were observed at the density of 60 kg, followed by the density of 15 kg, which indicates the presence of stress in high culture density and very low density. The activity of serum lysozyme in densities of 15 and 60 kg was significantly lower than the density of 30 kg. The lowest serum total antioxidant capacity value, osmolality, and complement activity (ACH50) and the highest serum ALT activity were observed in fish reared at the highest density. Serum globulin level was significantly higher and serum AST activity was lower at densities of 30 and 45 kg than the density of 60 kg. The lowest levels of serum cholesterol, low-density lipoproteins (LDL), high-density lipoproteins (HDL), and triglycerides were also observed at the density of 60 kg. The results showed that very low culture density, like high culture density, can have negative effects on the performance of rainbow trout. Therefore, medium densities (30 and 45 kg/m3) are recommended for rearing of this species.

The largest river in the southern basin of the Caspian Sea is Sefidroud, and the most important native fish of that river is the large head sea bass. Due to its long route and passing through different areas, this river is exposed to various contaminants including heavy metals. The aim of this research was to investigate the amount of bioaccumulation of lead and nickel heavy metals in L. capito muscle tissue in Sefidroud river. Three stations were selected along the route and in four seasons, 45 fish were caught by throwing nets. The samples were transferred to the laboratory in standard conditions and after biometrics, samples were taken from their muscles and the amount of these metals was determined by chemical digestion method and with the help of atomic absorption device. The results showed that the fishes caught in Sefidroud river in different seasons and stations were in the age range of +1, +3 and their average total weight was 221.72 ± 21.82 gr and their average total length was 25.19 ± 1.97 cm. The concentration of lead heavy metal L. capito in the muscle of Sefidroud 0.58±0.1 μg/g per gram of muscle and the mean test with one-way variance showed a significant difference between the stations in the seasons (P<0.05). The average nickel concentration in the muscles of one year was 4.1±83.4 μg/g of muscle, and the mean test with one-way variance showed a significant difference between the stations in the seasons (P<0.05). According to these results, the concentration of lead is low and according to the standards of consumption, it shows the permissible amount, but the amount of nickel in the muscles of Sefidroud big head fish sauce is high and even the safe consumption values ​​of some indicators have shown higher numbers.

The behavior of rural households in 11 non-coastal cities of Golestan province for fish consumption was evaluated. Data were collected through a designed questionnaire. In inferential analysis of the research, chi-square, Mann-Whitney and Friedman methods were used for ranking. About 73% of households in these areas source fish from fish markets and fishing grounds. 47% of households are interested in fried fish and 35.4% are stuffed fish. On average, they buy 6.88 kg of fish at a time. About 60% of them did not eat canned fish and their per capita consumption was 2 cans and their per capita consumption was 40 kg. 83% of them consumed more than the national average. The most important reasons for consuming their fish were one to four interests, cheapness, quality and freshness, and nutritional properties and value, respectively. Their favorite species are sturgeon, whitefish, Bream, mullet, respectively, but when buying, they choose farmed species and most of all, carp. Consumers over the age of 45 gave more importance to fresh fish, and people with higher education than diploma and women surveyed paid more attention to packaged fish than men. With increasing revenue, the tendency to diversify products and types of supply increased, and with increasing age, taste, cheapness, availability and non-extinction of fish became more important. They were very skilled in distinguishing fresh fish from spoiling fish for consumption. High-income and per capita households above the national average did not care about the endangered species. However, the possibility of access to marine fish and reduce fish prices in rural areas is suggested to increase consumption and study the separate consumption of marine fish and farming in rural areas.

The aim of this study was to increase the production efficiency of reared Great sturgeon (Huso huso) in the larval stage (after hatching until absorption of the yolk sac) under the corresponding influence of photoperiod and light intensity. In this study, the larvae from the after hatching to the complete absorption of the yolk sac were exposed to four light intensities (0-10; 70-100; 200-170 and 350-330lux) and five photoperiods (24L:00D; 16L:08D; 12L:12D; 08L: 16D and 00L: 24D) treatments and the control group. Each treatment and control group had three replications (70 g of larvae). At the end of the experiment, after sampling and biometry of the samples, growth factors including weight and final length, weight gain (WG), specific growth rate (SGR), condition factor (CF), body weight increase (BWI), daily growth (ADG) and survival rate (SR) were done using special mathematical formula. Also, some enzymatic, immune and biochemical factors of body plasma were measured and analyzed statistically. The results showed that although all growth indices (WG, SGR, CF, BWI and ADG) in the treatment of photoperiod of 24L:00D and light intensity of 100lux were in the maximum growth (p<0.05), but the maximum survival percentage of larvae (65.32%) compared to other treatments, especially the maximum growth treatment (7.41%), was observed in the photoperiod of 08L:16D and light intensity of 100lux treatment (p<0.05). Also, enzymatic, biochemical and immune indices were desirable conditions in the larvae of optimal growth treatment (treatment 11) compared to many other treatments (p<0.05). In total, the most suitable photoperiod and light intensity to increase the production efficiency of larvae with a yolk sac of reared great sturgeon, was the treatment of 08L:16D and 100lux.

This study aimed to evaluate the effects of different levels of dietary Quillaja saponin on the growth performence, digestive enzymes, water quality, and immune response of common carp in biofloc system. The fish (8.06 ± 0.59 g) were fed diets containing 0 (BC), 15 (BS1), 30 (BS2), and 60 (BS3) mg/kg saponin powder for 60 days. The growth performance and protease were significantly higher in the fish fed with a saponin diet in biofloc environment (P< 0.05) while no significant effects on Food conversion ratio and lipase enzyme (P> 0.05). Total ammonia nitrogen (TAN) concentration was significantly lower in the saponin-fed groups than in the control (P< 0.05). The highest serum total immunoglobulin levels, lysozyme, and complement (ACH50) activities were observed in the diet containing saponin powder in biofloc system (P< 0.05). The present results show that Quilaja saponin can be used as a potential feed additive for farmed fish in biofloc system.