Bull. Jpn. Soc. Fish. Oceanogr. 74(sp), Page 19-26, 2010   Influence of variability in reproductive traits on recruitment: the case of Atlantic cod Gadus morhua Michio Yoneda National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan e-mail: myoneda@fra.affrc.go.jp This review indicates the causes of variability in reproductive traits and the maternal effects on egg and larval growth and survival based on Atlantic cod Gadus morhua. Reproductive traits of fish are directly and indirectly influenced by environmental factors through the individual and population characteristics. Variations in the timing of onset of spawning, duration of spawning and the number of egg spawned at a season are due to not only the changes in water temperature and food availability, but also the influence of age and spawning experience. Spawning experience of a female affects egg diameter and egg buoyancy, which significantly affect growth and survival of eggs and larvae. However, male’s traits such as sperm density in milt have little effects on fertilization rate and larval growth. Simulation models based on reproductive traits at different age composition of spawning stock show a significant consequence of egg and larval production and viability. These observations show the importance of understanding the relationship between adult (reproductive) and offspring traits in fish species examined based on both field survey and laboratory experiments. Key words: Atlantic cod, reproductive traits, environmental factors, maternal effect, recruitment