Comparison of three in situ egg incubators for salmonid research applications

In situ egg incubators that retain fish embryos within gravel substrates are a valuable tool in salmonid research. Despite numerous designs, there have been few direct comparisons of the effectiveness of different incubator types. In this study, we compared the recovery, hatch, and survival rates of Chinook salmon ( Oncorhynchus tshawytscha) embryos among three types of incubators: A, a modified Whitlock-Vibert box; B, a cylindrical “egg tube”; and C, an inverted dome-shaped kitchen strainer that mimicked natural egg pockets with embryos developing between gravels. To assess their performance, we stocked chinook embryos in these three different types of incubators and buried them in gravels of artificial redds in three outdoor experimental river mesocosms. All incubator types supported salmon development (>30% hatch and >20% survival), with incubator type C exhibiting the lowest recovery but highest mean hatch and survival rates, though differences among types showed only weak to moderate statistical evidence. Hatch and survival rates were lower in the most downstream redds. This comparison provides a better understanding of how incubator designs affect the success of in situ fish incubation in salmonid research.