Stellwagen Bank Final EIS and Management Plan 



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increases along coastal waters of Massachusetts Bay 

 in waters north of Cape Ann sometime during 

 March, evidenced by copepod larvae. Copepod 

 (primarily Calanus fmmarchicus ) production 

 expands seaward toward the mouth of the Bay 

 during late April, and continues over the 

 southwestern Gulf of Maine as spring season 

 progresses. Peak zooplankton production occurs by 

 the end of May. Rapid decrease in zooplankton 

 abundance is evidenced in June. In the Gulf of 

 Maine there is a gradual decline in zooplankton 

 biomass from spring (i.e., June) to fall. 



Hydrographic factors in the Gulf of Maine control 

 the production, dispersal and survival of 

 zooplankton (Fish and Johnson, 1937). For 

 instance, water temperature dictates community 

 type; £md the horizontal distribution of zooplcuikton 

 is controlled by water circulation, stability, and 

 occasionally salinity. The dominant counter- 

 clockwise circulation pattern in the Gulf of Maine 

 moves all plankton, copepod eggs, and larvae in a 

 southwestward direction (unless they are situated in 

 areas protected from these circulation patterns). 



Due to the relatively "closed" nature of the Gulf 

 of Maine, temporal and spatial changes in 

 zooplankton quantities are primarily the result of 

 reproduction, growth, and mortality of endemic 

 species, such as Calanus . Pseudocalanus . Oithona . 

 and Microstella . 



c. Benthic Organisms 



Benthic invertebrates provide food for the vast 

 array of fish species found in the Stellwagen Bank, 

 and larger Gulf of Maine area. Invertebrate species 

 such as shrimps, crabs, worms, moUusks and 

 echinoderms sustain many groundfish species. The 

 health and availability of these food supplies are 

 integrally important in assisting the assessment of 

 variations in fish growth rates; changes in fish egg 

 production and survival rates of newly-hatched 

 young; deviations in normal fish migration routes 

 and times of migrations; and survival of juvenile and 

 adult fish stocks. 



To date, few studies have been conducted to 

 determine the particular composition of benthic 

 communities on offshore banks and ridges similar in 



makeup to Stellwagen Bank within the greater Gulf 

 of Maine/Massachusetts Bay region. Baseline 

 surveys of macrobenthic communities conducted at 

 Jeffreys Ledge, north of Stellwagen Bank, identified 

 149 faunal and floral species within horizontal and 

 vertical communities, and at various depths. At a 

 monitoring station near Jeffreys Ledge, two major, 

 ecologically distinct benthic communities have been 

 identified: an algal-polychaete community, and a 

 sponge-tunicate community (NOAA/NEFC, 1982). 

 However, these communities exist on rock or other 

 hard surfaces such as those comprising Jeffreys 

 Ledge; bottom sediments at Stellwagen Bank are 

 quite different. 



Investigations conducted by NOAA's Northeast 

 Fisheries Center into the macrobenthic communities 

 of the Georges Bank system included sampling 

 stations within the Stellwagen Bank vicinity; and 

 findings are appUcable to the overall New England 

 region, as well as to the Middle Atlantic Bight 

 (Theroux and Grosslein, 1987). There are four 

 dominant taxonomic groups of macrobenthic 

 invertebrates found in the Georges Bank/Gulf of 

 Maine region: annehds, crustaceans, moUusks, and 

 echinoderms. Dominance among these four groups, 

 however, differs significantly depending upon 

 whether species are ranked by biomass, or by 

 numerical abundance (density). In general, both the 

 largest biomass and the greater diversity tend to be 

 supported by gravel and sandy sediments (Campbell, 

 1987). Coarse-sand bottom sediments have been 

 shown to support the highest mean biomass of 

 macrobenthic organisms, often in the range of 371 

 g/m" (Theroux and Grosslein, 1987). Biomass and 

 diversity are also generally greatest around the rim 

 of the Gulf of Maine, in waters depths less than 100 

 meters (Campbell, 1987). 



Premised on the predominantly sand to pebbly- 

 sand composition of Stellwagen Bank's bottom 

 sediments, it is reasonable to suppose that 

 macrobenthic biomass on Stellwagen Bank is quite 

 high. Major taxonomic groups occurring on 

 Georges Bank have been ranked by both biomass, 

 and population density (Theroux and Grosslein, 

 1987: Table 1). 



