فصلنامه شیلات
سال هفتاد و چهارم شماره 1 (بهار 1400)

Rainbow trout fish fed one of the diets containing fresh kilka oil with 50 mg kg-1 of vitamin E 1)without (control A, FO50) or 2)with hydrolyzed protein (4% replacement for fishmeal) (treatment B, FO50HP), 50 mg kg-1 vitamin E with oxidized oil 3)without (treatment C, OO50) or 4)with hydrolyzed protein (treatment D, OO50Hp), 250 mg kg-1 vitamin E with oxidized oil 5)without (treatment E, OO250) or 6)with hydrolyzed protein (treatment F, OO250HP) in a completely randomized design (six treatments and three replications) for eight weeks. The lowest FCR was in treatment B and the highest was in treatment E (P< 0.05). The amount of other growth indices were higher (P< 0.05) in treatments A and B than other treatments. The highest and lowest concentrations of alanin amino transferase (ALT) occurred respectively in treatment C and treatments A and B (P< 0.05), the highest and lowest concentrations of aspartate amino transferase (AST) occurred in treatments C and D and treatment B (P< 0.05), respectively. The highest neutrophil (Nut) and the lowest lymphosit (Lym) percentages were in treatment E while the vise versa were observed in treatment C (P< 0.05). The phagocytosis amount was highest in treatments C and D while it was the lowest in treatment A (P< 0.05). The fillet 14: 1n-9 concentration was the highest in treatment F while it was the lowest in treatment B (P< 0.05). The fillet 18: 0 content was the highest in treatment A and the lowest in treatment D (P< 0.05). Treatment D showed the highest fillet 20: 4n- 6 content while treatment F had the lowest content (P< 0.05). Accordingly, vitamin E (50 mg kg-1 diet) with hydrolyzed protein (as a substitute for fish meal by 4%) would be able to prohibit the damages resulting from oxidative stress in growing rainbow trout.

Understanding the demographic characteristics of non-native species is very important for species and habitat management. The population structure and dynamics structure of river oriental prawn (Macrobrachium nipponense) were studied in three wetlands (Alma Gol, Alagol and Ajigol) of Golestan province, where the species is considered exotic species. A total of 6539 samples were collected and their biometric data recorded, the maximum total length of specimens ranged 90 -100mm. In this range, 4 age groups (0+,1+,2+and 3+) were identified. The growth parameters, obtained using von Bertalanffys growth function and Somer seasonal growth equation, were as L∞= 108 and 91 mm, K = 0.96/year and 0.98/year for males and females respectively. The lowest mortality rate was observed in age 1. The mean normal mortality rate for males and females was estimated to be M = 1.17 and M = 1.24, respectively. Total mortality rate, based on the length-converted catch curves equation, was estimated to be Z = 1.17 for males and Z = 1.17 for females. The total length at the first sexual maturity was estimated to be 46.9 mm for females and 52 mm for males. The optimum length for females was 64 mm, and for males was 76.8.

Large-head hairtail, Trichiurus lepturus, is one of the commercial fish at the Persian Gulf and Oman Sea waters, which is exploited to export outside markets. To present population dynamics and characteristics of this species, the fish caught by trawling method were analyzed from Kolahi to Dargahan areas in Hormozgan province waters. The von Bertalanffy growth equation (VBGF) was fitted to length-frequency data (n =771) to obtain a VBGF with the following parameters: L∞, K, and t0 were 88.83 cm, 0.10, and -0.07, respectively. The estimated value of total mortality (Z) and natural mortality (M) were 0.44 and 0.28 (year-1), respectively. Also, fishing mortality (F) was recorded as 0.16 year-1. Exploitation rate, corresponding to the maximum relative yield per recruit (E) was 0.36, and this fish in the present study caught capacity. Recruitment pattern showing maximum added yang fishes in September. The present results have to be considered with caution for fisheries management purposes as fishing effort is still in increasing phase. Long-term monitoring is required. To better understand the T. lepturus population dynamic and its fishery framework in the study region.

Morphological variations (morphometric and meristic traits), length-weight relationship parameters and condition factor were studied in autumn and spring populations of Alburnus chalcoides, collected from Sefid River (45 autumn and 113 spring) and Siahdarvishan (22 autumn and 28 spring) in the southern Caspian Sea basin. After anesthesia and fixation into the 4% buffered formalin, the samples were transferred to the laboratory and a total of 22 morphometric and 8 meristic characters were measured and counted using caliper and stereo-microscope, respectively. The results showed that the autumn and spring migratory populations of the studied species in the Sefid and Siahdarvishan rivers have significant differences in 7 and 2 morphometric traits (P<0.05), respectively, but not different in meristic characters (P>0.05). The results of the length-weight relationship parameters revealed that the Sefid River populations has an isometric growth pattern and the autumn and spring populations of the Siahdarvishan River showed positive allometric and isometric growth patterns, respectively.

Aeromonas hydrophila is one of the most important aquatic pathogens that cause fish losses and poor product quality in fish farms. The ability of Aeromonas hydrophila to form a biofilm makes this bacterium resistant to antibiotics. Hence, finding new antimicrobials with the potential to inhibit biofilm formation would be valuable. The aim of the present study was to evaluate the antibacterial and antibiofilm activity of the extract from Pseudoalteromonas piscicida, isolated from the sea anemone (Stichodactyla haddoni) against Aeromonas hydrophila. The Microdilution broth method was used to determine the minimum bactericidal concentration (MBC), and minimum inhibitory concentration (MIC) of Pseudoalteromonas piscicida extract. The anti-biofilm ability of this extract against formation of Aeromonas hydrophila biofilm was assessed using crystal violet staining method in 96-well plates. The results showed that the extract of Pseudoalteromonas piscicida inhibited the growth and biofilm formation of Aeromonas hydrophila at MIC=MBIC= 200 mg/ml. In addition, using physical and chemical treatments, it was shown that the active compounds are mainly proteinous in nature and are proteases. The results from the experimental challenge of zebrafish (Danio rerio) with the pathogen demonstrated that oral administration of Pseudoalteromonas piscicida extract in two safe doses of 200 and 400 mg mL-1 increased survival rates of the fish and decreased colonization of Aeromonas hydrophila in their intestine within 7 days. The results of the present study showed that Pseudoaltromonas picisidia extract contains bioactive compounds with antibacterial and antibiofilm ability against Aeromonas hydrophila and due to its low toxicity in fish, if purified, it can be a good alternative to antibiotics.

The aim of this study was to evaluate the histological effects of aflatoxin B1 (AFB1) and zearalenone (ZEA) on the liver tissue of the rainbow trout. In this study, 540 rainbow trout 12.07±0.23 g (Mean±SD), as 9 experimental treatments with three replications were fed separately and simultaneously with diets containing different concentrations of AFB1 and ZEA over 60 days. In this regard, the concentrations of 50 and 100 ppb AFB1 and 300 and 600 ppb of ZEA were used. At the end of the experimental period, the liver tissue was sampled and pathological changes were qualitatively and semi-quantitatively examined. The toxin-induced histological damage included necrosis and deformation of hepatocytes. The severity of tissue lesions increased with increasing dietary levels of AFB1 and ZEA separately and simultaneously. The results showed that the severity of lesions was higher in fish receiving diets containing combinations of AFB1 and ZEA in comparison to other treatments.

The River brown trout (Salmo trutta fario) is one of the freshwater fish species that is endangered in Iran due to overfishing, habitat destruction and demolation of special substates for spawning. Three sampling sites were considered from different parts of Chalous River (upstream, middle and downstream of river) to predict the habitat suitability of the River brown trout. A set of environmental variables (physico-chemical and structural variables) was monthly sampled at each sampling site (in total 19 variables). The environmental variables were simultaneously colledted with the presence/absence of the river trout (12 samples presence and 24 samples absence) during one-year study period (2017-2018). Based on the prediction of the generalized linear model, there was a significant difference between the presence and absence of fish in the sampling sites regarding all the environmental factors (after excluding the variables with high correlation) (p< 0.01). The results of the model showed that increase of the water flow velocity, river depth and dissolved oxygen concentration (especially in the upper part of the river) may increase the probability of fish presence in the river. In contrast, increasing physical and structural variables such as water temperature, the river width and the distance from the source and also increasing the concentration of water quality variables such as salinity, nutrients (such as nitrate and phosphate), chemical oxygen demand and suspended solids gradually might decrease the presence of fish.