Comparative study on the major elements, total bacteria, and rainbow trout egg quality parameters in recirculating and flow-through systems

A recirculating hatchery system (RHS) and a flow-through system (FTS) in terms of major macro elements (Ca, Mg, Na and k), some microelements (Fe and Cu), total bacteria and quality characteristics of Rainbow trout eggs and larvae were comparatively studied. A recirculating system (RHS) and a flow-through system (FTS) were designed for incubating the eggs and rearing the yolk-sac larvae. Fertilized eggs were distributed (5000 eggs in each tray) in four replicates and incubated under the standard conditions until yolk sac absorption. Total bacteria and macro/micro elements were measured at one-week interval. Eyed egg percentage, hatching rate, growth, and survival rate of larvae were measured. In the FTS and RHS, percentages of the eyed eggs were 79.75% and 79.01% respectively, and hatching rates were 70.31% and 63.65%, respectively. There were no significant differences amongst the values of Ca, Mg, and Na during the experimental period and between two systems. K Values in the RHS were significantly higher than in the FTS during the egg incubation period. Fe Values in the RHS were more than in the FTS, and increased during the study period in both systems. The values of total bacteria in the RHS were significantly higher than in the FTS.  Despite the differences observed between the experimental systems, the designed RHS can be used for incubating the eggs and rearing the yolk-sac larvae in rainbow trout hatcheries, because of its simplicity, low water consumption, and acceptable efficiency.