The Lifelong Consequences of Life History Variation in Gulf of Maine Cod

Trait variability of conspecifics often correlates with differences in life history that can influence population dynamics and consequently fisheries productivity. Distinct forms of Atlantic cod Gadus morhua occupying different types of habitat in New England waters have been reported by fishermen for at least 130 years. For instance, “rock” (i.e., red) cod have regionally consistent body shapes (box-truss analysis), habitat preferences (acoustic telemetry-derived depth), and movement behaviors correlating with body color (red-to-green-ratio) that all suggest a more resident life-history strategy. In addition, earlier sampling at a shallow offshore ledge revealed differences in size, growth, and diet preferences of red cod and co-occurring olive (i.e., holotype) cod. Here we explored the age-structure, growth, and trophic ecology of cod in the context of morphometry and region. We predicted that inshore and offshore red cod would grow at similarly low rates, reaching smaller maximum sizes than olive cod, and that invertebrates would persist in their diets across age-classes, contributing to lower trophic position relative to olive cod. These slower growing, smaller residents occupying highly structured coastal waters and offshore ledges may comprise an increasing proportion of the Gulf of Maine stock, with large implications for future productivity.