Air stripping of fish eggs, the effectiveness of the procedure, and the impact on brood stock management in two salmonid fish, rainbow trout and brown trout. Hi, my name is Radoslaw Kowalski. We are from the Institute of Animal Reproduction and Food Research, Polish Academy of Science in Olsztyn.
We would like to present the air spawning method of salmonid fish. Hand stripping is a traditional spawning procedure in fish. This procedure may cause damage to the eggs by hand resulting in lower fertilization potential of the eggs.
An alternative method utilizes gas pressure to deplete eggs from the fish body. This method is called air spawning. Air spawning is a method in which fish eggs are collected without massaging the abdomen of the fish.
A syringe and needle are used for injection of the gas into the fish body cavity. Air stripping of fish eggs. In this procedure gas pressure should be controlled and the best condition is maintained when its value is below one bar.
Air flow should also be controlled. For salmonid fish, one and a half liters per minute is the efficient speed of gas exhaustion. And optimum speed should be maintained because higher speed may not obtain all the eggs while a slower speed may unnecessarily prolong the procedure.
The syringe should be connected with a screwed needle to avoid needle detachment caused by the gas pressure. The fish should be anesthetized and carefully dried out before spawning. The fish is placed on a slant bed about 35 to 40 degrees.
The needle should be quickly inserted below the abdominal fins. The eggs are freely removed by the gas until only singular eggs are being removed from the fish body. Gentle massage of the abdomen can help to remove the excess gas from the fish body.
After spawning, the fish is gently transferred to the tank with a water flow. Fish release to the tank after air spawning may initially swim on the surface of the water. After several minutes the fish releases the remaining gas while swimming and starts swimming normally.
The obtained eggs are very clean and free from blood or fecal contamination.Results. The duration of egg collection by the hand stripping method was shorter than air stripping in both species. The method of stripping did not influence the total volume of eggs obtained by either hand or air stripping methods.
The ovarian fluid in rainbow trout after hand stripping was lower than after air stripping. The hatching rate in rainbow trout was also significantly higher after air stripping. Conclusions, air stripping was not faster than the hand stripping method.
Air stripping was beneficial to rainbow trout egg quality but not to brown trout eggs. Since no special skills are required to carry out the air stripping procedure a similar quantity and quality of eggs can be obtained by both skilled and non-skilled hatchery workers. Air stripping procedure is a promising option for new hatcheries seeking an egg collection procedure characterized by a high level of reproducibility and efficiency as well as little or no experience by the operators.
