نشریه تحقیقات منابع طبیعی تجدید شونده
سال سوم شماره 4 (پیاپی 10، زمستان 1391)

Light is an important factor in fish growth because of its effect on fish activity and metabolism. This survey was conducted to study the effects of different light colors on growth and survival of koi carp Cyprinus carpio larvae for two months. The initial weight of Koi larvae was 0.0402±0.0016g. Larvae were examined in three treatments including blue (L1), green (L2) and red (L3) light colors. Each treatment had three replicates each containing 30 koi larvae. Photoperiod was set to 14-h light and 10-h dark. Feeding was done twice a day using Biomar food. 15 fish were sampled from each tank and their body weight was measured after every other week. Survival rate was also evaluated at the end of experiment. Results showed significant differences in the growth indices between three treatments of L1, L2 and L3 (p<0.05). Blue light caused the highest growth rate followed by green and red light. No significant difference was observed in the survival rate between the treatments (p>0.05). Results showed that light color can significantly effect on koi larvae growth with the optimum growth condition by application of blue light.

This study was conducted to investigate the effects of daphnia (Daphnia magna) enriched with essential fatty acids on growth and survival larval kutum (Rutilus frisii kutum) of the Caspian Sea over two weeks. The Kutum fish fries had initial weight of 52.62 mg which were in triplicate with daphnia enriched with essential fatty acids, non-enriched daphnia and hand-fed biomar diet. The results indicated significant difference in growth performance between three treatments (p<0.05). The maximum specific growth rate (8.5±00 % d-1), weight gain (120.48±2.1 g) and final total length (31.3±0.1 cm) were observed in the daphnia treatment enriched by essential fatty acid. However, there was no significant difference in survival rate between treatments (p>0.05). This study showed that enrichment of daphnia with essential fatty acid enhances growth performance.

This study was aimed to identify the fish species and their abundances in Godarkhosh River, Ilam Province. Sampling was done using an electro shocker device equipped by 200 volts electricity generator from 5 different stations throughout the river within 100 meters of each station. Fish specimens at each station were caught, in triplicates, according to the Zypyn method specified for closed condition. Samples were immediately fixed by formalin, transferred to the laboratory and identified based on their meristic and morphometric characteristics using the identification key books of fish. Results showed the presence of eight species belongs to three different families. Cyprinidae was the most abundant family (92.4%) with six species from different genera. Nemachilidae and Mastacembelidae families each by one species had also 6.28% and 1.31% of the species abundance, respectively. Fish species captured in this study were included Garra rufa, Cyprinion macrostomum, Capoeta trutta, Alburnus mossulensis, Carasobrbus luteus, Mastacembelus mastacembelus, Tor grypus, and Oxynoemacheilus frenatus. The most abundance species was Cyprinion macrostomum (31.3%) followed by the Alburnus mossulensis (29.4%) and G. rufa (24.4%). Mastacembelus mastacembelus (1.05%) had also the lowest abundance among the fish species.

The main objective of the present study is to determine spatial and temporal distribution of common carp in depths 2-100 m in Iranian waters of the Caspian Sea, during 2007-2011. Seasonal sampling data collected by using bottom trawl in 57 stations. The results showed that the maximum catch and average of CPUE (±S.E.) were 39.0 kg and 0.98±0.35 kg/0.5 hr-1 in depths of 2-10 m in 2011 spring. The bulk stock concentrated in depths <20 m in eastern region (from Amirabad to Hasangholi), which seasonal averages of CPUE were 0.69±0.62, 1.08±0.41, 0.16±0.10 and 0.46±0.14 kg/0.5 hr-1 in spring, summer, autumn and winter in the region, respectively. High concentration of carp in the eastern region could be due to stock enhancement program of carp which conducted by Iran Fisheries Organization.

In this study, effect of feeding diets containing different amounts of pigment lutein, the amount of growth and blood factors of rainbow trout (Oncorhynchus mykiss) were investigated. This study for eight weeks, on 600 numbers of rainbow trout (average weight 93.02±0/64 g), in a control group and three treatments (each with three replicates) was performed. Fish fed three times daily with a commercial diet (GFT2) containing different amounts of lutein (0, 14, 16 and 20 mg/kg) was conducted. The results showed that the treatments studied had significant difference in weight and body length of fish (p<0.05), but no significant difference (p>0.05) in performance parameters of growth and food consumption including FCR, SGR, GR, BWI, CF followed by survival rate. Results of the blood sampling showed that WBC, RBC, lymphocytes, and IgM were significant differed between the treatments (p<0.05), but monocytes and neutrophils didn’t show significant difference between treatments (p>0.05).

Aquaculture and environment have considerable interaction impacts on each other. In this study, the effect of education on environmental attitudes and behavior of trout farmers were investigated. The experiment was applicable using a researcher-made questionnaires and environmental training package. The validity of questionnaire was confirmed by the university professors and researchers of Fisheries Organization. Reliability of the Questionnaire with 15 tests showed Cronbach's alpha coefficient of 0.84. The statistical population was included 150 farmers with monoculture farms that their farms’ effluent had been discharged to surface water. The sample consisted of 63 persons in two control and experimental groups. The results showed inappropriate attitude of respondents before offering environmental training package (About 34% correct answers), while their acquaintance was significantly changed after presentation of the training package (p<0.05). Besides, 79% of respondents are not used any wastewater refining methods. However, training package could change behaviors in the experimental group and they announced readiness to wastewater treatment with low-cost procedures. No significant correlation was observed between age, education and aquaculture acquaintance with environmental behavior and attitudes. The results of present study showed that education had an important role in the environmental behavior of coldwater fish farmers, especially to prevent the pollution caused by farms’ waste water.