Journal of Fisheries
Year:2011 | Volume:64 | Issue:2|Papers Count:8

Variation in growth, feed utilization and survival was assessed in sturgeon fingerlings of Beluga fed different dietary lipid levels. All diets were iso-nitrogenous (protein=45%) comprising 3.4-3.7 kcal digestible energy g-1. Triplicate groups of 35 fingerling Beluga with a mean initial wet weight of 2.14 ± 0.07 g (± SD) were fed with four experimental diets containing 6.7, 10.5, 14 and 17% crude fat for 48 days (water volume: 100 L.; water change rate: 1.4 L min-1). There were significant differences in final weight, body weight increase, specific growth rate, production index, hepatosomatic index, protein efficiency ratio, productive protein value and feed utilization ratio of fingerling Beluga (P<0.05). Increasing lipid levels to 14% level improved the above indices. However, condition factor and survival were not affected by different dietary lipid levels (P>0.05). The best growth rate, survival, feed utilization were obtained at 14% lipid level with DE: CP ratio of 79.9 kcal g-1. These results indicate that optimal dietary lipid level for fingerling Beluga is about 14% for these diets.

Nowadays, importance of keeping and presentation of fresh fish, with regard to consumer preference for fresh fish rather than frozen fish, is increasing. So, determination of fish shelf-life, to find its consumption time, due to high perishability of fish, is important. This study was aimed to investigate the process of spoil changes and determining the shelf-life of rainbow trout (Oncorhynchus mykiss) fillet during storage period in refrigerator (4oC). For this purpose, rainbow trout fillets were kept in refrigerator for 18 days and the changes of free fatty acids (FFA), tiobarbitoric acid (TBA), total volatile bases nitrogen (TVB-N), total viable count (TVC) and sensory evaluations were assessed. The results showed that the quantity of chemical indices increased during storage period. With regard to the standard quantity of TBA, TVB-N and TVC and also sensory evaluation of panel group, the samples were out of the specified standard on 5 day. Considering of correlation between chemical and microbial indices with total acceptability showed that the most precise indices for shelf-life determination of rainbow trout fillet is TVC (6 log cfu/g) indicator and TVB-N (about 25 mg in 100 g fillet). Accordingly, rainbow trout fillet can be kept in refrigerator for 5 days.

Caspian kutum is one of the most commercial fishes that migrates for spawning from the Caspian Sea to the rivers each year. Consequently, it can be exposed to several agricultural and industrial pollutants. In this study, to estimate the fish spermatogenesis in polluted waters, the direct effect of diazinon were investigated using in vitro testis culture of the Caspian kutum with 10, 100 and 200 μg/ ml concentrations for 3 and 6 days. With increase of diazinon concentrations and exposed time, harmful effects of diazinon on spermatogenesis and testis structure increased. The inhibition of spermatogenesis and necrotic germ cells were more visible in 200 mg/ml in 6th day. Since, appropriate quality and quantity of gametes can verify the successful reproduction in fish, water pollution over consecutive years can be a serious threat on kutum populations.

This study investigated ontogeny of fatty acid profile in common carp larvae to determine nutritional requirements with a view to improving product quality from hatching to 33 days post hatching at the governmental warm water fish aquaculture center of Shahid Rajaee in Sari, Mazandaran, Iran. Larvae were collected randomly at 1, 3, 7, 11, 15, 19, 26 and 33 days post hatch. Larvae were fed with rotifer (Brachionus calyciflorus) from day 3 to day 7, and then with dry diet from day 8 onwards. Profiles of saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids showed significant changes. From the beginning to the end of experiment, total saturated fatty acid decreased at the level of 2 % and monounsaturated and polyunsaturated increased by 7.46 % and 1.26 %, respectively. Fluctuations in the composition of fatty acids in various periods reflect preferential utilization of fatty acids for energy production. Marine carp larvae metabolized apparently dietary linolenic acid to eicosapentaenoic acid and docosahexaenoic acid, and dietary linoleic acid to arachidonic acid.

Population of Vimba vimba persa was investigated using microsatellite markers originated from two regions along the Iranian coastline of Southern Caspian Sea (Anzali Lagoon and Havigh River in Gilan province). Totally 153 alleles were identified. The highest number of alleles per CA3 loci was 17 and the lowest 3 in Z8145 loci with means of 7.6. Observed and expected heterozygosity averages were 0.79 and 0.76, respectively. Most cases deviated significantly from Hardy-Weinberg equilibrium (p£0.01). The estimation of Fst (p£0.01) identified significantly two populations of Vimba vimba persa in the Caspian Sea. Studies of this kind assist conservation of this species, sustainable harvest and restocking of the populations.

In this investigation effects of two stunning methods 1) ice asphyxia, 2) direct immersion of fish into bath containing previous water dilution of clove oil that were killed by blow on the head were compared with common fish slaughtering method: removing fish from water and exposed to the air (asphyxia). Effects of these two methods on meat quality and stress responses in common carp were evaluated. Results revealed that anaesthetizing and killing procedures significantly affected the meat quality in common carp. Both rigor index and pH varied significantly during the trail postmortem between the experimental groups. Maximal rigor index (77.6%) was observed after 3 hours post mortem in the asphyxia group. Rigor index reached maximum at 24 (44.2%) and 60 h (55.1%) post mortem for the ice and clove oil group. Fish subjected to clove oil showed a less intense than those in the other group although they had a longer lasting rigor state. Mean muscle pH of fish was 6.34 for asphyxia, 6.53 for ice group and 6.99 for clove oil immediately after death. Fish of the group clove oil had the lowest driploss at 96h postmortem. Stress blood indicators in asphyxia group were significantly higher than other two groups and the control group (unstressed fish). The data presented in the experiment expressed that fish of the group received clove oil had significantly higher quality and less stress response than other groups.

The effect of rainbow trout farms outflow in the Haraz river on benthic macroinvertebrates and the self-purification potential of river was investigated from each of ten selected stations along four farms. Benthic macroinvertebrates was investigated for different seasons a year by taking five samples. About 170000 macroinvertebrate specimens at 34 genera, 32 families and 12 orders were isolated and distinguished in this study. Maximum abundance at most stations was possessed by order Ephemeroptera, of which Baetis sp. followed by Acentrella sp. constituted 97.9% of the Ephemeroptera at all stations. Indices of EPT richness, EPT percentage and EPT/CHIR (Ephemeroptera+Plecoptera+Trichoptera/Chironomidae) decreased at the immediate vicinity of the fish farms outflows, and increased upon distancing from the farms. On the basis of HFBI (Hilsenhoff Family Biotic Index) index, four grades of good, suitable, relatively poor and poor water qualities were distinguished at all the sampling stations. The combined results of biotic indices indicated that pollution was higher at the stations at the immediate vicinity of the fish farms outflows than the preceding ones, and the self-purification potential of water increased upon distancing from the farms, peaking to a significant level at a distance of 3.5 km.

This study investigated the inhibitory effects of Bacillus licheniformis on G1 and G2 aflatoxins in culture media and Kilka fish meal. Two concentrations of aflatoxins (8 and 12 ppb for G1 and G2) and (2 and 4 ml from aflatoxins standard per 50g of fish meal) were used in culture media and Kilka fish meal respectively. The doses of bacillus were 3 and 4% for this experiment. Changes of aflatoxins and the bacterium growth were evaluated using HPLC and spectrophotometer (OD: 600 l) respectively. Culture media results show that G1 and G2 concentrations decreased significantly (P<0.05) by 99.9 and 99.4%, 99.2 and 98.2% respectively (for 3% Bacillus), and 100 and 100%, 100 and 99.6%, respectively (for 4% Bacillus). In fish meal, concentrations of G1 and G2 decreased significantly (P<0.05) by 75.8 and 66.1%, 77.7 and 80.1% (for 3% Bacillus with 2 and 4 ml aflatoxins standard) and 95.4 and 81.7%, 98.9 and 89.3 % (for 4% Bacillus with 2 and 4 ml aflatoxins standard), respectively. The results show that Bacillus licheniformis is able to decrease significantly (P<0.05) G1 and G2 aflatoxins in culture media and fish meal and is recommended to be used as a biological tool in fish meal industry.