Penobscot Bay Watch

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(Heck et al. 1989).

The mapped EFH designations mirror the long held knowledge that inshore waters are principal habitat for juvenile cod. The distribution of juvenile cod observed in the latter half of 19th century and early part of this century was summarized by Bigelow and Schroeder (1953). They described young-of-the-year cod living in very shoal water to the littoral zone, and small, presumably one-year-olds, along the coast within two fathoms (@ 4 m m) in summer.

From the contemporary NMFS trawl survey catch in the Southern New England-Georges Bank region, water temperature was determined to be a factor in explaining interseasonal spatial and depth distribution of age-1-4 cod. However, water temperatures were insufficient to explain distributional differences among age classes (Wigley and Serchuk 1992). From a slightly earlier time series of research vessel catches in the Gulf of Maine, as well as collections on Georges Bank and Southern New England, Wigley and Gabriel (1991) noted juvenile (<37 cm) cod inhabiting a mean depth of 62 m in the spring and 75 m in the autumn with seasonal occurrence at minimum depths of about 9 m in both seasons.

Within the Gulf of Maine, juvenile concentrations occurred between Jeffrey's Ledge and Cape Cod in spring and were more restricted to Massachusetts Bay in fall. Lower densities of juveniles also occurred all along the 100 m isobath off New Hampshire/ Maine coast during both seasons. However, the NMFS survey completes relatively few stations nearshore in the northern part of the Gulf due to the rough bottom habitats that are untrawlable with traditional survey gear.

The most southern inshore portion of the Gulf of Maine is more accessible to research vessels and has been covered by the MDMF survey. The occurrence of juvenile cod (<35 cm) matched all temperatures (<13°C) and depths sampled in spring (5-80 m), but during fall surveys, young cod tended to occur at deeper (15-50 m) and cooler (<17°C) sampling stations. The juvenile cod catch per tow was highest along the north shore of Massachusetts Bay and Cape Ann/ Ipswich Bay in spring (500-1,765 fish/tow) and fall (500-2,925 fish/tow), as well as the tip of Cape Cod in spring (200-500 fish/tow), and throughout Cape Cod Bay in fall (500-2,925 fish/tow) (NEFMC 1998). Age-groups 0 and 1 cod predominate in the fall survey with the highest densities of 0-group cod usually occurring at alongshore stations, catches invariably associated with bycatch of live bottom material [e.g., sulphur sponge (Cliona), kelp, spaghetti grass " (Codium), and eelgrass (A. Howe, pers. comm.)].

Status of Eelgrass
The presence of eelgrass beds may be an equally important factor influencing distribution and abundance of post-settled cod juveniles in the Gulf of Maine as documented in the Canadian maritime provinces and certain countries bordering the Northeast Atlantic. However, eelgrass has been in general decline in U.S. coastal regions for over half a century. There are multiple stressors and disturbances contributing to loss of eelgrass acreage (Short et al. 1987, Muehlstein and Porter 1991; Nixon 1995). Wasting disease caused by the pathogenic marine slime mold, Labyrinthua sp. Nov, is responsible for epidemic losses a half century ago and has re-occurred in some areas. In many estuaries and coastal areas, sediment loading (turbidity) from the watershed and increased anthropogenic nitrogen loading (eutrophication) via groundwater has stimulated algal competitors that shade and stress plants and significantly reduce stem density and depth of the plants. Fishing gear that cuts shoots has also been implicated.

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