Estimating the importance of maternal age, size, and spawning experience to recruitment of Atlantic cod (Gadus morhua)

Empirical studies have demonstrated the importance of maternal characteristics to egg and larval viability in Atlantic cod (Gadus morhua) and other marine teleosts. The effects of these advantages on total reproductive output of individual fish have not yet been studied. A model of an Atlantic cod population was constructed to determine the contribution of offspring by spawners of different spawning experience. First-, second-, and third-time spawners consisted of cod ages 1–9 years old and experienced spawners consisted of ages 10 and 11. Experienced spawners contributed 10.1–12.4 times more offspring surviving to age 1 than did less experienced spawners. Reproductive efforts by first- and second-time spawners were relatively unimportant. These insights are at odds with traditional maximum sustainable yield based management and lax management, both of which favor a population dominated by young breeders and ignore the large per capita production of recruits by experienced spawners. To be managed for biological survival and commercial viability, northwest Atlantic cod will require legal protection to prevent the harvest of these oldest ages of cod.