Effects of maternal influences and timing of spawning on intraspecific variations in larval qualities of the Kuruma prawn Marsupenaeus japonicus

Decreases in intraspecific variations in offspring qualities resulting from reductions in female body size in harvested populations can reduce the ability of these species to adapt to variations in environmental conditions. This, in turn, may result in greater fluctuations in recruitment of resources. In species in which offspring quality differs by female parent size, preserving differences and preventing limitations in female size among populations would be important. The effects of maternal factors on intraspecific variations in larval quality of the Kuruma prawn (Marsupenaeus japonicus) were analyzed by determining the relationships between larval variability (body size and resistance to starvation) and maternal variability (maternal body size, spawning timing, and maternal body condition) in the laboratory from June to October 2015. In addition, temporal variations in parental body size of fished M. japonicus stock were examined by field investigation for ten years between 1996 and 2010 in Bungo-suido Channel, Japan. Body size and starvation resistance of hatched larvae varied by spawning timing (spawning date) and corresponded with seasonal availability of food for larvae in the field. Larger females produced larger larvae with stronger starvation resistance. The mean size of harvested female prawns has decreased significantly over time. Stocks of M. japonicus with reduced mean female size would show reductions in intraspecific variations in quality and quantity of larvae at the population level, resulting from observed maternal influences and size-dependent female reproductive potential. If fishing activity reduces body size, marine reserves can be used as a possible management option.