The Fishery Biology Program of the Northeast Fisheries Science Center provides this resource to assist with age determination of fish and shellfish species from the Northwest Atlantic. Released in its current form in 1997, this resource represents the fruit of many years of accumulated expertise. Techniques for aging sixteen species of fish or shellfish are given here, based on growth marks in scales, otoliths, and shells. From Atlantic Butterfish through Yellowtail Flounder, these detailed descriptions and black-and-white images should be of valuable assistance to researchers.