1Hokkaido Central Fisheries Experimental Station, Yoichi, Hokkaido 046-8555, 2Ocean Research Institute of the University of Tokyo, Nakano, Tokyo 164-8639, 3Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 981-8555, Japan
Video recordings of the behavior of 50 adult shira-uo Salangichthys microdon in an aquarium were analyzed to reveal their spawning behavior. Shira-uo showed unique spawning behavior that a pair shake their bodies, with the male sticking his gonopore into the female's one using the anal fin scales as a sucker. The mating behavior was that a female descended from the usual circular swimming in the upper layer to the bottom layer, males checking each other there crowded around the female and exchanged body charges to compete for the female, and a pair formed as a result of the male-male competition. The paired female led the male upward, and they spawned and ejaculated. However the pair did not always succeed in spawning and ejaculation and the low success rate may be due to the female's choice of mate. Furthermore, it was suggested that the female repeatedly spawned a small number of eggs with every spawning success by reiterating the process of mating.