A comparative analysis of air and manual stripping techniques in female rainbow trout (Oncorhynchus mykiss) broodstocks

Numerous techniques are used in aquaculture to stripped eggs from fish broodstocks. The most common is the manual method, where the abdomen of the fish is gently massaged to extract the eggs. Alternatively, injecting gas pressure into the abdominal cavity can facilitate the release of eggs with potentially fewer negative impacts on the welfare and egg quality. This study compared the pneumatic stripping methods and the manual spawning method in rainbow trout (Oncorhynchus mykiss) spawners. The study focused on the effects of these techniques on the quality of the harvested eggs, relative fertility, stripping duration, and pH of the ovarian fluids. The findings revealed that maintaining a gas flow rate at 1.5 L min(-1) during stripping is crucial to prevent post-stripping mortality of the broodstocks. The pneumatic method demonstrated a shorter duration of egg retrieval (39.5 s) compared to the manual method (42 s). Notably, there were no significant differences observed in ovarian fluid pH across the various methods (p<0.05). Overall, pneumatic egg extraction leads to higher-quality eggs with a greater hatching rate compared to the manual method. Considering the positive results of the pneumatic stripping and its high level of repeatability and efficiency, it can be used instead of the traditional method in rainbow trout hatcheries.