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The trade-offs between habitat use and frequency of feeding in the face of predation risk are processes consistent with density-dependent habitat use and mortality. Although empirical evidence of density-dependent usage off Newfoundland is contradictory, stock size/recruitment may not yet be large enough following the northern cod stock collapse to induce significant density-dependent effects on a large spatial scale. Nevertheless, behavioral research details ways age-0 juveniles respond to spatial heterogeneity, the consequences for fitness through utilization of resources, and the intraspecific competitive effects which emphasizes the importance of habitat availability and quality in determining recruitment success.

Gulf of Maine Coastal Marine Environment and Juvenile Cod Distribution

Coastal Environment
The margin of the Gulf of Maine is similar to the Canadian coastal zone of higher latitudes with the exception that the latter generally has more imposing headlands and bathymetric relief, narrower beaches, and a more steeply sloping shore zone. The coastline of the northern Gulf between Passamaquoddy Bay and Cape Elizabeth, Maine, is also rugged, wave-exposed, and rock-framed. Within hundreds of indented bays and coves are thousands of islands and ledges.

The subtidal seafloor is largely hard-bottom (ledge and boulder), often giving way to cobble/gravel, and sediment within < 9 m depth. Submerged bedrock outcroppings and rocks provide bathymetric relief and substantial vegetative algal habitats.

From Cape Elizabeth to Cape Cod, the coast is characterized by long sandy beaches, unconsolidated cliffs and bluffs, and occasional rocky headlands, most prominently Cape Ann and Marblehead. With the exception of the headland littoral zone, the nearshore seafloor is generally wave-rippled coarse sand broken occasionally by restricted patches of cobble. Numerous barrier beaches protect estuaries and occasionally extensive salt marshes lying behind them.

Along the southern part of the coast, in particular, but near entrances of protected inlets or river deltas, sand may be vegetated with eelgrass meadows. Sublittoral hard bottom relief including sand ripples, troughs, empty shells, worm tubes, motile or sessile invertebrate taxa (e.g., mussels, starfish, urchins, anemones, hydrozoans, bryozoans, ascidians, and sponges) and marine vegetation provides valuable interspersion of cover types for age-0 juvenile nurser, habitat similar to the nearshore regions of the Canadian maritime provinces. However, unlike some areas north of the international border, the coastal zone is the only known source of recruits to the Gulf of Maine cod stock.

Juvenile Cod Distribution
For the Gulf of Maine cod stock, the distribution pattern of eggs, larvae, and juveniles has been demarcated along the coast from eastern Maine to Cape Cod; hence, the western perimeter of the Gulf has been designated EFH for these life stages (NEFMC 1998). The EFH designation for juveniles (<35 cm) was based on presence/absence as identified by several sources: NMFS and MDMF inshore bottom trawl surveys (1963-97 and 1978-97, respectively), NMFS MARMAP ichthyoplankton survey (1977-87), and NOAA's Estuarine Living Marine Resources (ELMR) program encompassing abundance records for 13 major bays and harbors and four river systems.

Results from additional, less systematic or more spatially restricted coastal sampling efforts (the basis for ELMR classifications with some exceptions) are now being compiled and should reveal more complete information on cod distribution. A pertinent example is the notation that juvenile Atlantic cod were seined only at night from eelgrass meadows of Nauset Harbor, Cape Cod

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