Rainbow Trout Oncorhynchus Mykiss Juveniles Research Articles

Laboratory studies of fish entrainment sampling using a screw centrifugal impeller pump

AbstractObjectiveRegulatory legislation in both the United States and Canada requires water users with medium to high intake volumes to monitor entrainment losses to determine effects and to assess potential mitigation strategies to reduce harm to fish. Recent studies have recommended the use of both increased sampling frequency and sampling volume to characterize fish entrainment for large power plants on the Great Lakes. There is little doubt that increasing the flow rate and volume of water collected for sampling reduces the uncertainty in estimates of annual entrainment. Depending on the type of pump and the pumping flow rate used for entrainment sampling, considerable damage to fish larvae can occur. A screw‐type centrifugal pump has many qualities that make it ideal for entrainment sampling, but it has not yet been used as a sampling device for fish entrainment applications at power plants or other large industrial water users. The objective of this study was to determine mortality of entrainable fish eggs and larvae due to passage through a screw‐type centrifugal pump.MethodsIn a laboratory setting, Lake Trout Salvelinus namaycush eggs and larvae, Lake Whitefish Coregonus clupeaformis eggs, and Rainbow Trout Oncorhynchus mykiss juveniles were passed through a screw‐type centrifugal pump at three treatment flow rates: 39.5, 47.3, and 59.1 m3/h. Fish and eggs were monitored for mortality posttreatment and again at 24 and 48 h.ResultAcross treatments, very few mortalities were observed. Species specific moralities were four larval Lake Trout, one Lake Whitefish egg, and one juvenile Rainbow Trout. No mortality was observed for Lake Trout eggs.ConclusionThe present study identified high egg and larval survival (≥99%) after passage through a screw‐type centrifugal pump. High survival reduces error associated with identification and counting of entrained organisms, which provides more accurate estimates of annual entrainment losses.

Effects of an Enzyme Complex-Treated Rice Protein Concentrate on Growth Performance and Feed Utilization of Rainbow Trout Oncorhynchus mykiss Juveniles

This study investigated the effect of the inclusion of an enzyme complex-treated rice protein concentrate (RPC) in an extruded diet of juvenile rainbow trout (Oncorhynchus mykiss). A mixture of RPC, corn gluten and soybean meal was pretreated with an enzyme complex before extrusion processing of the diets. An enzyme complex-pretreated RPC (5, 10 and 15%) was formulated with 20% fish meal. A diet without RPC was used as a control. A total of 240 rainbow trouts with an average body weight of 6.04 g were placed in 12 rectangular glass aquaria and fed one of the experimental diets at apparent satiation for 12 weeks. There were no significant differences in growth, feed intake and survival among the groups. Slightly inferior weight gain and specific growth rate were observed in the RPC15E group compared to those in the other groups. The protein and ash contents of the whole body of the final fish were not significantly different among all groups, but the lipid content was significantly lower than that of the control when the dietary RPC level was >10%. Protein digestibility was negatively affected by increased RPC levels in diet. Significantly lower phosphorus digestibility was observed in fish fed the diet containing 5% enzyme-treated RPC than the control. Although there was no significant difference in lipid digestibility in all groups, significantly lower lipid retention was observed in fish fed a diet formulated with more than 10% RPC. These results suggest that the inclusion of RPC in the diet affects lipid retention and the content of rainbow trout. It also decreased protein digestibility. In conclusion, rainbow trout can be fed an extruded diet formulated with 20% fishmeal and 10% enzyme-treated RPC without negative effects on fish growth.

Effects of grapeVitis viniferaseed oil supplementation on growth, survival, fatty acid profiles, antioxidant contents and blood parameters in rainbow troutOncorhynchus mykiss

In this study, effects of grape Vitis vinifera seed oil supplementation (0, 250 mg, 500 mg, 1,000 mg/kg feed) for 60 days on rainbow trout Oncorhynchus mykiss juveniles were investigated. The average final fish weights were not different between the control group and 500 mg/kg feed group (p > .05), but 250 mg/kg feed group were lower than those of the control group, and 1,000 mg/kg feed group were higher than those of the control group. Although the SFA, MUFA and n3 ratios of the control group were higher than that of the other groups, no statistical difference was found. The highest fatty acids in the fish were palmitic acid C 16: 0 in the SFA group and C 18: 1n-9 and docosahexaenoic acid C 22: 6n-3 in the PUFA group. The EPA ratio was significantly increased in all groups compared with the control group. The DHA ratio was significantly higher in the control group than in the experimental groups, and there was no difference between the experimental groups. Urea were significantly lower in the 250 mg/kg feed group. Total protein and aspartate aminotransferase were significantly increased in the 1,000 mg/kg feed group. Only the 1,000 mg/kg feed group showed an increase in antioxidant activities, and this concentration also yielded positive results in terms of growth performance, survival rates, fatty acid composition and antioxidant enzyme activities in rainbow trout juvenile and can be used as a natural feed additive.