نشریه علوم و فنون شیلات
سال سوم شماره 4 (پیاپی 9، زمستان 1393)

The effect of replacement of dietary soybean meal with broad bean flour on rainbow trout (Oncorhynchus mykiss) with average weight of 12.5 ± 0.09 g in 4 levels (15, 30, 45 and 60%) during 7 weeks trial was examined. The results showed that substitution of soybean meal up to 30% replacement) did not have any negative impact on fish growth performance. However, significant difference in red blood cells count and hematocrit percent were found between the experimental groups and the control (P0.05) from 15% replacement. This study showed that up to 30% fish meal replacement with broad bean flour in the diet of rainbow trout had no negative impact on the growth performance, blood factors and survival of fish.

The combined effect of different levels of dietary n-3 HUFAs [eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)] with α-Tocopherol on growth parameters (final weight, SGR, FCR, and some health indices (hematocrit, plasma lipid and lipoprotein levels) of the Caspian trout fry, Salmotruttacaspius, was investigated. Six experimental diets containing three different dietary levels of n-3 HUFAs (Low: 1 0.5, DHA EPA, Medium: 2 1, DHA EPA, High: 4 2, DHA EPA g/100g diet) with two different levels of α-Tocopherol (Low: 300 and High: 1000 mg/kg diet) were prepared and named: LL, LH, ML, MH, HL, HH (HUFA/α-Tocopherol) groups, respectively. Fries (600 ± 25 mg) were randomly distributed in tanks (50 fries per tank) and were fed with the experimental diets for 10 weeks. The work was conducted in triplicates. Results showed that the SGR and body weight were significantly higher in the MH group than other groups. Hematological parameters, especially plasma lipids and lipoproteins were more influenced by the dietary n-3 HUFA and vitamin E and interaction between vitamin E and n-3 HUFA has minimal effect on these parameters. Results of this study suggested that increasing of dietary n-3 HUFA could improved growth performance and enhance health in the Caspian trout fry when appropriate level of α- Tocopherol supplemented.

The effect of packaging type on the shelf life of gutted farmed rainbow trout (Oncorhynchus mykiss) stored in refrigerator (3°C) was investigated. The fish was gutted and washed at room temperature. They were packed individually in polyethylene-polyamide bags in three experimental packaging: the presence of air, vacuum, and modified atmosphere (60% carbon dioxide, 10% oxygen and 30% nitrogen). The samples were stored in refrigerator up to 15 days and evaluated for the microbiological enumerations, chemical and physical analysis at days 0, 3, 6, 9, 12 and 15. The numbers of mesophilic, enterobacteria and lactic acid bacteria in the various treatments were not significantly different, during the storage. The number of psychrotrophic bacterium was not significantly different up to the 12th days of storage in all the experimental groups, whereas the bacterial count was significantly lower in the modified atmosphere packaging. Changes in the acid values and TBARS were not also significant in all the experimental groups during the storage. The amount of drip loss in all treatments increased with time. In the 12th and 15th days of storage, the loss was significantly higher in the vacuumed samples. In all treatments, the hardness value of meat was considerably decreased in the third day compared to the first day of storage. The present study revealed that if the rainbow trout properly washed and gutted in the hygienic conditions and stored at a suitable temperature, the shelf life was extended up to nine days without using any specific packaging. Furthermore, the packaging conditions used in this study did not improve the shelf life of the gutted farmed rainbow trout stored at 3ºC.

Based on the macro-invertebrate community and physico-chemical indices, water quality of the Tajan River in 6 stations along 80 km of the river length was assessed. Monthly sampling was conducted for one year (September 2011 to August 2012), using a surber with 30.5 × 30.5 cm dimensions and a 60μ mesh net for the benthic invertebrates sampling. The identified macro-invertebrates belonged to 31 families, 12 orders and 5 classes, the highest and the lowest abundance of which belonged to Psychodidae and Chironomidae, respectively. Based on Hilsenhoff Family Biotic Index, the research stations were classified into 4 qualitative categories, viz. excellent, good, fair, and fairly poor. Stations 1 and 5, respectively, showed the highest and lowest HFBI index. The highest and the lowest values for the Shannon–Weiner index were recorded in station 1 and station 2, respectively. The results of physicochemical parameters indicated reduced dissolved oxygen in the stations 2 and 5, and increased TDS in station 2 and 1 and increased nitrite and ammonium in station 3. Results of Spearman correlation coefficients between biotic indices and physicochemical variables revealed significant relationship between DO, TDS, EC, PO4 and water flow with HFBI and Shannon-Weiner indices. This study showed, generally pollution in stations 2 and 5 has reduced water quality in these stations.

The effects of stress on body cortisol and reproductive performance of guppy, Poeciliar eticulata, was evaluated on 90 immature female fish (0.29 ± 0.03g body weight). The experiment, carried for 30 days in three replications, included: the control (without any manipulation), handling stress (daily holding in a net for 2 minutes) and feeding with the cortisol-treated diet (500 mg per kg food). After this period, reproduction was induced by adding male fish to the remaining females in each tank. No significant difference was observed in growth rate among the treatments (p=0.001). The mortality rate and body cortisol content in both handling and cortisol-fed treatments were significantly higher than that in the control group (p=0.000). The minimum and maximum number of embryos was observed in the control and cortisol-fed groups, respectively. Our results indicated that such manipulations have negative effects on survival and reproductive efficiency and change whole-body cortisol content. Therefore, the measurement of whole-body cortisol content could be a suitable criterion for determining physiological condition in small laboratory fishes.

The effect of two salinity concentrations (35 and 40 ‰) on the daily feeding and burrowing activities of the sea cucumber, Holothuria parva was investigated, using the nutritional parameters (intestinal indices, organic materials, and the absorption efficiency). Although no significant difference between the initial and final sections of the intestinal gut of sea cucumbers in two saline conditions was found, the maximum level of intestinal indices, organic material and absorption efficiency was associated with the 40‰ salinity. The survey results displayed that sea cucumber had better feeding activity in 40‰ than 35‰ salinity.

The effect of Pediococcus pentosaceus as a probiotic on the growth and immunological factors of the Siberian sturgeon, Acipencer baerii, was assessed. For this purpose, 180 fish specimens of 143.3±0.01 g body weight were randomly distributed in 12 fiberglass tanks (15 fish per tank) and fed with four diets containing 107, 108 and 109 bacterial cells per gram, respectively. The forth diet (control) contained no probiotics. Results showed significant improvement in FCR, PER, SGR and BWI in groups fed on diets containing probiotics compared to the control group. However, CF decreased in the probiotic- treated groups, though not significant. The result of immunological factors indicated increased lyzozyme activity, ACH50 and total igM. The best result from the assessment of immune factors was observed in the fish fed with 109 bacteial cell per gram of diet.

In recent years the use of rotifers as live food for rearing fish larvae and crustacean is very important. Growth and density is considered as an important factor in the production of rotifers. In this study, the effect of three different concentrations (1.5×106, 3×106, 4.5×106 cell/ml-1) of green algae, Tetraselmis Suecica, on growth, reproduction, body and egg size of marine rotifer, Brachionus plicatilis were investigated. Rotifers were cultured in standard conditions in 500 ml plastic containers. The initial density of rotifers in different treatments was 30 ind/ml. Based on the results, the highest density (331/67 ± 13/32) were showed in high concentration, which were significantly (P 0.05). The present study showed that the concentration of algae Tetraselmis suecica might be used in marine rotifer breeding and changing various concentrations, can produce various sizes of rotifers.