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[en] Between 2002 and 2003, an outbreak of a trout's mass death occurred at the intensive fish culture a Peruvian rural town (Marcara, Huaraz, Peru) where 15,000 from 20,000 fish died. Our objective in the present study was to investigate the high mortality of the trout biomass occurred in period of two months. This study was conducted after the peak of the outbreak has occurred. We collected samples of fishes, water and fish foodstuff which were examined for aflatoxin, metals, toxics and bacteria. We interviewed people who administered the feed pellet. Feed sample preparation, transport and storage. The processing of fish feed was at room temperature which was below 16 deg C. Once prepared the diet it was keep under an appropriate room for a few days before sending to Marcara town. Fishes. 20,000 immature trout larval of rainbow trout (Oncorhynchus mykiss) was acquired from an official Peruvian fish culture. The fishes were fed twice a day. Adjusted of feed ration was based from the monthly sample weight. Pellet sample analysis. The samples were analyzed for aflatoxin Bl (AFB1) according to the method previously published. The sensitivity is 0.1 μg per 1 kg of sample. During the fish development until the peak of the outbreak, the foodstuff to fishes was maintained in plastic bags. At this time the storage room temperature was 18-20 deg. C between 1.00-2.00 P.M. and the humidity rose close to 90 % at the Marcara facilities. Mortality development and Effect on survival. The fishes maintained in 4 pods had a normal surviving until end of November, less than 10 specimen dead by month. The fish outbreaks started the first week of December and continuing until the fourth week of January totalizing 15,000 dead fish from 20,000. The survival of the fish at the first month was less than 50 %. The mortality continues throughout January totalizing 15,000 dead fish and leaving only 25% survival. Laboratory data. The collected samples for analysis were frozen and transported in dry ice to the analysis laboratory. We took the samples on January 23 and it was analyzed on January 25. Aflatoxin Bl was detected in three samples of fish muscle and in the 3 samples of fish feed but it was negative in the 3 water samples. The AFB1 concentration was 10 times in the fish feed than in the fish muscle. In spite of heavy metal residues (lead, mercury and arsenic) were found in the fish samples, those concentrations were below the permissible levels. Volatile toxic residues were negative in water, fish and feed. Only the fish feed samples were contaminated by bacteria (Staphylococcus aureaus). Under favourable conditions of temperature and humidity, the Aspergillus flavus grows on certain foods and feeds, resulting in the production of aflatoxin Bl. For the trout, the highest admissible amount of AFBI in feed is 0.1 μg per kg. The data showed suggest that an improper handling of fish foodstuff (18-20 deg. C and 90 % humidity) was the cause growing of mould and/or spores and consequently it produced an increased concentration of AFBI in fish feed. Liver is strategically located between intestinal tract and general circulation. As AFBI concentration ranged in liver between 10 and 100 ppb, this level is capable to produce an acute hepatotoxicity in the fish stocks. (author)
[en] A river channel survey was completed along three reaches (totalling 14.3km), i.e. an unregulated stretch and two regulated reaches (with reduced flows) of the Soca River to assess the spatial pattern of CGU type, size, hydraulics and distribution. In addition, one regulated reach was re-surveyed at different discharges to investigate the dynamics of CGUs and their relationship with flow. CGUs were classified and mapped using visual assessment and physical measurements of the hydraulic characteristics (velocity and depth) in each CGU. The effect of flow regulation on the hydraulic character of the river becomes apparent by highlighting differences in the types of CGUs present between the regulated and unregulated reaches. Reduced flows from river regulation also significantly reduces the size of CGUs, alters their hydraulic character, and affects the longitudinal distribution of types by creating greater habitat fragmentation. Hydraulic preferences for spawning habitat of marble trout (Salmo marmoratus) were obtained from previous research. The hydraulic character of CGUs were analysed at different discharges and combined with the hydraulic preferences of the species to evaluate the impact of flow regulation on habitat availability. Analysis shows that intermediate measured flow provides increased spawning habitat availability in the chosen reach for this target species.
[en] A solid-phase radioimmunoassay (RIA) employing miniature G-25 Sephadex columns and a single isotope was evaluated for simultaneous measurement of T3(3,5,3'-triiodo-L-thyronine) and T4(L-thyroxine) in trout plasma. The method was judged reliable based on the characteristics of the standard curves, the high and consistent recoveries of T3(87.0 or 86.7 percent) and T4 (103 or 98 percent) added either singly or in combination, low inter-(<8 percent) and intra-assay (<7 percent) coefficients of variation, predictable values of T3 and T4 after plasma dilution, and acceptable correlations between hormone values obtained using either the simultaneous or single RIA methods (rsub(T3) = 0.89; rsub(T4) = 0.91). It is concluded that the simultaneous RIA with its savings in time, plasma volume, and reagents can be used to advantage to measure T3 and T4 in plasma of trout and presumably other vertebrates
[en] Chromogranin A (CgA) is a protein that is present in many mammalian endocrine cells and co-secreted with their resident hormones. The authors have demonstrated the presence of CgA by immunohistology in the ultimobranchial glands and corpuscles of Stannius of rainbow trout. CgA was also detected by radioimmunoassay in the medium of incubated coho salmon ultimobranchial glands. Their observations demonstrate the presence of CgA in endocrine glands of evolutionarily divergent species. These observations are consistent with the hypothesis that CgA participates in the secretory process of a wide variety of hormones. 18 references, 1 figure, 1 table
[en] Industrially, common problems arise with the deboning pin bone process, where Atlantic Salmon (Salmo salar) and Rainbow Trout (Oncorhynchus mykiss) fillets, post rigor, are subjected to a pulling process to remove the pin bones from the fillet. This study measured the length of pin bones from two species of fish and two different industrial graded weights, and then used a texture analyser and µCT X-ray to measure the pulling force, break point and volume of the pin bones of both species of fish. Results showed that salmon pin bones required significantly higher pulling force to remove pin bones from the fish fillet when compared with Trout pin bones. Interestingly Trout pin bones were significantly longer and stronger than Salmon pin bones, but had significantly lower volume. This research has progressed the issues surrounding pin boning industrially, however, more studies are required in order to understand if these differences affect the overall deboning pin bone process.
[en] Techniques for reducing adverse effects of river and lake regulation are being developed and tested within the framework of the Norwegian Biotope Adjustment Programme. The programme is illustrated by studies of a river flowing through the wetland area, Lesjaleirene, which has been drained and channelized to provide additional agricultural land. The channelized river has a homogeneous sand substrate. Experimental placement of rocks and stones increased brown trout densities, especially in areas in contact with the river banks. The new areas of rocks and stones provide cover for fish as well as a greater variation in depth and flow conditions. (Author)
[en] The immunostimulating and therapeutic properties of Ginkgo biloba (GB) have always been the focus of traditional medicine over thousands of years. During last decade, special attentions were paid to use of GB in aquaculture to enhance fish health and survival. In the present study, we investigated for the first time the immunogenic effects of dietary GB against oxidative and toxicity induced by organophosphate pesticide, diazinon. In non-diazinon-exposed fish, the plasma total immunoglobulin, lysozyme activity, and peroxidase activity significantly elevated after 60-day experiment in fish supplemented with 1 and 2 g GB/kg diet (p < 0.05). The respiratory burst activity and complement activity significantly increased only in groups supplemented with 0.5 g GB/kg diet (p < 0.05). Furthermore, the peroxidase activity, total immunoglobulin, and lysozyme activity significantly declined in groups supplemented with 4 g GB/kg diet during feeding trial (p < 0.05). There were no significant differences in expression of interleukin 1 beta (IL-1β) and transforming growth factor beta 1 (TGF-β1) genes in kidney between control group (non-GB-supplemented fish) and GB-supplemented fish (p > 0.05). In diazinon-exposed fish, all immunity components significantly decreased during exposure in control and those fed 0.5 and 4 g GB/kg diet (p < 0.05). In fish fed 1 and 2 g GB/kg diet, no alternations were found in immunity components during exposure period (p > 0.05). In addition, diazinon induced the expression of IL-1β and TGF-β1 genes in control and fish fed 0.5 and 4 g GB/kg diet (p < 0.05). No significant changes were observed in expression of IL-1β and TGF-β1 genes in fish supplemented with 1 and 2 g GB/kg (p > 0.05). In conclusion, the results of the present study suggest an immunogenic role for dietary GB at optimum dietary levels (1–2 g GB/kg diet) against toxicity induced by diazinon. Nevertheless, GB at high dietary levels (4 g GB/kg diet) showed immunosuppressive effects, which makes it necessary to optimize its levels in diet.