نشریه پژوهش های ماهی شناسی کاربردی
سال پنجم شماره 1 (بهار 1396)

The purpose of this study was to determine the diet spectrum, feeding preference and feeding rate of sand goby. The present study was carried out in the Kaboodval, Zaringol and Shirabad Streams in summer 2008. In this regard, 104, 30 and 62 fish individuals were analyzed in the mentioned streams, respectively, and their diet regime were investigated. Based on the vacuity index, the sand goby presented in the Kaboodval, Zaringol and Shirabad Streams was classified in relatively gluttonous, relatively low fed and gluttonous groups, respectively. In this study, the food spectrum of the sand goby was broad and the fish was fed with the larvae of insects, crustaceans, Oligochaeta, gastropods and goby fish. Furthermore, the determination of digestive tract contains showed that the sand goby was fed with thirteen different kinds of food preys, in that Diptera (mainly Chironomid larvae) and Ephemeroptera in the Kaboodval and Shirabad Streams, the Ephemeroptera, Trichoptera and Diptera (mainly Chironomid larvae) in the Zaringol Stream were a most common food preys. According to the values of the Ivlev's selectivity index, the Ephemeroptera showed positive values in all three Streams and Diptera had negative values. According to Fp index, Diptera was also considered as the main food prey in the Kaboodval and Shirabad Streams while it was secondary food prey in the Zaringol Stream. Based on the results of this study, it can be concluded that the sand goby displays a generalistic and highly flexible feeding strategy due to its ability to use locally available food resources.

The present study was performed to aim the comparison of the body shape of large scale tongue sole (C. arel) fish from coastal waters of north Persian Gulf. To fulfill this purpose, a total of 120 fish individuals captured by bottom trawlers from the four stations of Kangan, Bushehr, Daylam, and Abadan were used. In order to study traditional morphometrics, 13 morphometric traits (measurable) and 6 meristic traits (countable) were selected and examined. Results of morphometric and meristic comparison showed a significant overlap among studied populations. Based on these results, the total length of fish was measured from 206.51 to 265.04 mm, 110-130 soft rays from the dorsal fin, 10-16 soft rays from the caudal fin and 82-98 soft rays from anal fin were counted. The mean number of scales between two lateral lines was 7.72. Comparison of means resulted from traditional morphometric study revealed no significant differentiation between different stations. The results of geometric morphometrics revealed significant differences between the studied stations in that the highest difference was belonged to specimens from Abadan and Kangan, whereas the lowest difference was observed in the specimens from Bushehr and Daylam samples. Based on the results of the present study, it can be concluded that geometric morphometric method possesses higher potential to discriminate populations of the studied species compared to the traditional method.

In the present study, 610 C. macrostomum individuals were caught from March to July 2012 using beach seine in order to evaluate some growth parameters. Observed sex ratio of male to female was 1:1.19, statistical analysis showed that male and female ratios are the same in the population. The maximum total length and weight were recorded130 mm, 25.94 g and 115 mm 18.22 g, for females and males respectively. The weight-length relation for females was W=0.0076 TL3.15 and the weight - length relation for males was W=0.0076 TL3.15 and this value for the population was W=0.0075TL3.16. Results indicated that the growth pattern for this species in the studied region was positive allometric. The highest condition factor for males was observed in April and July and the lowest value was in March. For females the highest and lowest condition factors were in July and March respectively.

The study of the digestive enzymes activity in fishes is very necessary to determine enzyme activity and its digestive capability. This study was carried out to identify changes of digestive enzymes in fertilized eggs and larval stages before and after yolk sac absorption in Silver Carp (H. molitrix). For this purpose, sampling was performed from different larval stages of fertilized eggs after mitotic division, at the beginning of gastrulation, hatching time, two third absorption of yolk sac, in the initiation and 3 days after exogenous feeding. In this study, the rate of amylase activity was manually measured while lipase activity was evaluated by enzymatic method using spectrophotometer. Specific activities of lipase and amylase enzymes for the larva with three days after exogenous feeding were significantly higher than the other larval stages. In general, specific activities of amylase and lipase enzymes showed increasing trend during sampling stages.

The present research was conducted in order to determine age and growth of the Caspian trout (S. caspius) in Iranian coastline of the Caspian Sea (western part of Mazandaran province) from 2013 till 2015. For this purpose, biometric parameters such as length, weight and age of fifty fish individuals were recorded using back-calculation method. Based on this method, the average length of fish at ages 1, 2 and 3 years old were 18.98±3.5, 30.5±7.24 and 41.7±9.1 cm respectively. As these age groups are under the maturity age, they don’t approach to near the coast lines in spawning seasons. Therefore, these groups were not observed in the catch composition. Average length of the fish 4, 5, 6 and 7 years old were determined as 53.9, 63.7, 68.6 and 74 cm respectively. In the present study, the minimum and maximum recorded age of this species were 4 and 7 years (mean=5.6) respectively, and the most frequent age group was 5 and the frequency of 6 and 7 age groups has been remarkable. The average length and weight of the Caspian trout in the catch composition were measured 69.2±6.2 cm (minimum 57 and maximum 81 cm) and 3323±677 g (2400 to 5600 g) respectively. The growth parameters including growth coefficient (K), length-infinity (L∞) and ´ø were measured as 0.18, 104 cm and 3.289 respectively. L∞ and K for the species were in the acceptable range.

In the present study, the effects of different levels of dietary ginger powder (Zingiber officinale) on some of mucous immune parameters, hematological parameters and growth performance was investigated in Caspian Kutum (R. kutum) fingerlings. 420 individuals (mean weight: 3.69±1.60 g) were randomly distributed into12 tanks and fed with different levels of ginger [0(control), 1, 5 and 10 g/kg] for 8 weeks. Results showed that the highest mucus alkaline phosphatase activity, total protein levels and lysozyme activity were observed for the fish fed with the highest levels of ginger. The numbers of red and white blood cells (RBC and WBC), hematocrit (HCT) and hemoglobin (HB) were significantly different between treatments of ginger and the control fish. The highest number of lymphocytes was observed in fish fed with higher levels of ginger, whereas the lowest number in control group, indicating significant differences between the fish fed with ginger and control group fish in this regard. However, no significant difference was observed with regard to the number of monocytes and eosinophil between different treatments. Furthermore, the fish fed with dietary ginger showed improved growth performance compared to the control group, and the treatment fish fed with 10 g dietary ginger had the highest growth rate. Results of this study showed that the use of ginger causes increase in the activity of mucosalimmune parameters, hematological factors and growth performance compared to the control group.

The aim of this study was to evaluate the effect of edible hot water extraction seaweed, Sargassum angustifoliom, on haematological parameters and survival rate of rainbow trout (O. mykiss) against Yersinia ruckeri. For this purpose, 300 rainbow trout specimens (5.82±0.22 g mean weight) were purchased from a local fish farm and transferred to the laboratory. After 14 days acclimation to the experimental conditions, the fish were randomly divided into five groups with triplicates. Fish were fed with 0 (control), 50, 100, 200 and 400 mg/kg of S. angustifoliom extraction for 56 days. The fish blood samples were takenfor fish exposed with Y. ruckeri bacteria at the end of the experimental period (56 days).The number of red blood cells (RBC), white blood cells (WBC), the percentage of haematocrit and the concentration of haemoglobin were then measured. Results showed that the fish fed with different concentrations of seaweed extraction possessed higher survivability rate and more suitable haematological parameters compared to the control group 56 days after feeding and being exposed to Yersinia bacteria. Meanwhile, the number of RBCs, WBCs, and the percentage of haematocrit and concentration of haemoglobin for the fish fed with 400mg/kg hot extraction of seaweed significantly increased at the end of experimental period. Furthermore, resistance against to the Yersiniosis for these fish increased by using this concentration of seaweed extraction. Therefore the present study suggested that 400mg/kg of seaweed extraction could improve rainbow trout blood parameters and increase the resistance against Yersiniosis.

The present study was performed in order to evaluate the effect of complementary iron on some of the growth indices in Ship sturgeon (A. nudiventris) juveniles. One control group (iron free) and four iron (FeSo4 .7 H 2o) treatment groups with different concentrations (100, 200, 250, 300 mg/kg) were considered in this study. The diets were added to the semi-pure diet for 60 days. Hand-feeding was conducted three times per day. The biometric assessment of the fish was performed at the end of the fourth week and at the end of experimental period. Results showed that the fish fed with 100 mg/Kg iron possessed the highest weight while the weight of the fish fed with 300 mg/Kg had the was not so much increased. Furthermore, the maximum total length, SGR, PER, FE, % BWI, ADG and survivability rate were observed for the fish fed with the first treatment (100mg/Kg) at the end of the experimental period. Results also showed that the fish weight (48.85±4.64g), SGR (1.51±0.043), PER (0.214±0.008), FE (53.54±2.023), BMW% (147.25±6.39), the average daily growth (0.485±0.015), hepatic iron (18.06±0.103), available iron in muscles (10.01±0.09), HSI (4.22±0.35) and the rate of survivability (91.11±7.69) were significantly different between the juveniles fed with different concentration of iron. The minimum amount of FCR (1.87±0.071) was observed for the fish fed with the first treatment, however there was no significant difference for CF between the fish fed with different treatments).The maximum amount of protein percentage and the minimum amount of fat percentage in carcass composition were observed for the fish from the first treatment (63.44±0.62) and the fourth treatment (10±0) respectively. Results of this study determined that some of growth indices in the sturgeon juveniles are significantly affected by the dietary iron (ferrous sulfate). Therefore, it seems that the diet containing 100 mg/kg iron can be considered as optimum diet in rearing condition and for this weight range of fish.