Does the Primary Production from Macroalgae and Seagrass Contribute to the Production of Inshore Juvenile Cod in Coastal Newfoundland?

Macroalgae beds and seagrass meadows have been shown to represent significant habitat for juvenile Atlantic cod and other important fish species in coastal Newfoundland and across the North Atlantic. Most studies relate the higher densities, survival and growth of larval fish in vegetated habitats to increases in habitat complexity that provide shelter from predation, access to prey and refuge from strong water currents. Vegetated habitats also have significantly higher primary productivity than nearby barren substrates with contributions from macroalgae, seagrass and phytoplankton however, the relative contribution of these primary producers to larval cod production is not well known. In this study stable isotopes of nitrogen and carbon are used to examine the role of seagrass and macroalgae as contributors to the planktonic prey of inshore larval cod and their competitors in contrast to those caught offshore. While stable isotopes cannot distinguish between habitats in the nearshore (vegetated vs barren) given the potential for sloughing and movement of macrophyte material between habitats, they are suitable to distinguish the carbon sources of inshore and offshore fish.