Some of the more common species collected in 

 the lower estuary have been cod, pollack, sil- 

 ver hake, mud hake, cunner, winter flounder 

 and spiny dogfish. The mummichog, or killi- 

 fish, is ubiquitous but favors tidal creeks and 

 the shallow water of the upper estuary. Winter 

 and smooth flounders, fourspined sticklebacks, 

 eels and tomcod are also common in the upper 

 estuary. 



Table 1 provides a partial list of both 

 fish and invertebrates that have been found in 

 the Sheepscot estuary. 



The bottom organisms which constitute 

 a dietary staple of many kinds of fish are abund- 

 ant everywhere. Some of the chief food organ- 

 isms of this sort - shrimps ( Crago septemspin - 

 osus particularly), cumaceans, amphipods, 

 small bivalves and polychaete worms - are ex- 

 tremely numerous and widely distributed. 

 Small forage fish are also abundant: herring 

 brit, young alewives, silversides and mummi- 

 chogs, especially during the warmer months. 



There are a few predators which are im- 

 portant because they attack species of commer- 

 cial value. The spiny dogfish and the harbor 

 seal are very common and range far into the 

 estuary. Their depredations are at least trou- 

 blesome to the fishermen if perhaps less serious 

 to the populations preyed upon. The double 

 crested cormorant is a fish eater and probably 

 like the two predators cited above, may be more 

 a pest than a menace. On the other hand, the 

 green crab (Carcinides maenas) has been demon- 

 strated to be a serious predator on the soft- shell 

 clam and one of the chief factors involved in the 

 recent decline in the populations of this shellfish 

 (Glude, 1955; Dow and Wallace, 1952). The 

 relative scarcity of this crab in the upper estu- 

 ary where the water reaches very low salinity 

 levels may partly account for the successful 

 sets of clams that frequently occur in that area. 

 These ubiquitous and hardy creatures do, how- 

 ever, manage to stray in small numbers so far 

 into the estuary as to mingle with similarly 

 vagrant fresh water species, such as dragon fly 

 larvae . It should not be assumed from this that 

 they normally penetrate fresh water . EXie to 

 the seasonal and tidal fluctuations in the loca- 

 tion of the transition zone between fresh and 

 brackish water, mixed populations of euryhaline 



marine and fresh water organisms are common 

 in the innermost part of the estuary. 



Great blue herons and kingfishers are 

 numerous among the salt marshes and along the 

 banks of the estuary and the river. Red breasted 

 mergansers, American mergansers, ospreys 

 and other fish -eating birds have been observed 

 from time to time, also. The American mer- 

 ganser appears to be a serious predator on 

 young salmon (White, 1939; Huntsman, 1941). 



Some mention should be made here of the 

 characteristic aquatic vegetation in the estuary. 

 No attempt has been made to list all of even the 

 common species, but there are a few which can- 

 not escape notice. The common rockweeds 

 Ascophyllum nodosum and Fucus vesiculosus 

 are abundant on rocks and other solid substrata 

 from the open coast to slightly above the falls at 

 Sheepscot Village, between the tide marks . 

 Below the low tide level, sometimes exposed at 

 spring low water are Irish moss ( Chondrus 

 crispus) and kelp (Laminaria spp.) but they do 

 not penetrate as far into the estuary as the other 

 species mentioned. Enter omorpha intestinalis, 

 a green alga, is common in the upper estuary, 

 extending almost to fresh water in the summer- 

 time. This plant was found, along with the 

 diatom Melosira spp., to constitute an important 

 item in the diet of the mummichog ( Fundulus ). 



Eel grass (Zostera marina) is present 

 in shallow protected places from the seaward 

 end of the estuary to somewhat above the falls 

 at Sheepscot Village, and it appears to be in- 

 creasing in abundance . Marsh grasses (Spartina 

 alterniflora and S. patens) border the upper 

 estuary and many tidal inlets elsewhere, often 

 forming broad expanses of salt marsh. S. alter- 

 niflora was found to extend up the estuary some- 

 what beyond the average penetration of saline 

 water, where it was associated with various 

 species of sedge (Scirpus). 



SUMMARY 



EXiring the years 1954 - 1956, a general 

 ecological and hydrographic survey was made of 

 the estuary of the Sheepscot River, Maine. This 

 was done to provide background information for 

 further more detailed studies of Atlantic salmon, 

 clams, alewives, smelt, oysters and other 



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