Age cannot be determined at the time of tagging and it is usually not possible to determine the age at capture because fishermen only report the capture and they usually do not return the fish for age determination. [...] We estimate this model from survey growth data and use the model to estimate length at age (L@A) and to estimate the age of a tagged fish given the year and season (i.e. [...] In addition, the size of a cod in the spring may be considerably less than in the fall, especially for younger cod. [...] In this paper we develop a time-series VonB growth model to estimate the L@A of Northern cod from the various sizes that have been tagged and at the various times of the year and locations that tagging has occurred. [...] The model is designed to account for the features we identified in the exploratory data analyses above.