Habitat Associations of Juvenile Cod in Nearshore Waters

ABSTRACT

Abiotic conditions greatly influence the distribution and abundance of marine organisms during early life-history phases. For instance, factors such as habitat heterogeneity often affect the dispersive phase of marine fishes, and then diminish in importance as species approach maturity and are influenced more so by biological processes. While recently settled fish are typically found in shallow, complex habitats such as seagrass beds, the degree to which juveniles associate with specific habitats as they grow and migrate into deeper water remains less clear. To better understand fish habitat preferences during early life-history phases, a literature review was conducted on habitat use by juvenile Atlantic cod (Gadus morhua), followed by an evaluation of the relationships between habitat characteristics and bottom trawl, video and hook-and-line data in the western Gulf of Maine. The review revealed that juvenile densities, survival, and growth rates were higher in structured than in less complex habitats. Meanwhile, older juvenile cod that were sampled in the western Gulf of Maine were far more abundant on cobble and granule/pebble habitat than on mud or sand bottom. These results suggest habitat heterogeneity is tightly coupled with biological processes (e.g., predation), and its functional role extends well beyond settlement even for highly mobile species.

KEYWORDS:

• Gadus morhua
• essential fish habitat
• population dynamics
• cobble-ledge
• groundfish

Acknowledgments

The Maine-Department of Marine Resources provided trawl data for this study. A. Lyons, C. Ritz, A. Swafford, J. Gaudette, and C. Brown provided assistance in the field with video assays/hook-and-line sampling and/or in the laboratory scoring video surveys. P. Wells (F/V Tenacious) and V. Balzano (F/V North Star) provided vessel services.

Funding

This project was supported by the National Marine Fisheries Service (NMFS), Northeast Region Office (NERO), Cooperative Research Partners Initiative (CRPI).