Effects of body size on mating behavior and spawning success of the Japanese spiny lobster Panulirus japonicus (von Siebold, 1824) (Decapoda: Palinuridae): implications for broodstock management techniques

Abstract

We investigated the effects of male and female body size on the mating behavior and spawning success of the Japanese spiny lobster Panulirus japonicus (von Siebold, 1824) under laboratory conditions in order to develop broodstock management techniques. The lobsters were divided into three body-size groups of each sex based on the maximum sizes observed in landings and the minimum sizes at sexual maturity. Mating behavior was observed by video recording 39 pairs in nine combinations among the large-, medium-, and small-size groups of each sex. Mating behavior was observed in 21 pairs, 20 females laid eggs, and clutch size and egg fertilization rates were determined. The effects of male and female body size (continuous variable) on mating behavior were also analyzed. Mating behavior was categorized into four phases: approach, upright posture, copulation, and separation. Smaller males tended to have difficulty manipulating and holding larger females. The total number of copulations per couple and duration of a single copulation were higher in smaller males, suggesting that females require multiple matings to increase the probability of fertilization. The rate of spawning success tended to increase when females mated with larger males. Fertilization rates were unaffected by male or female body size and were 90.0-100%, except in one pair of a small-size male and a medium-size female (3.5%). Clutch size was significantly affected by female but not male body size. Our mating experiments suggest that small-size males are not recommended for use as broodstock for larviculture.