food webs in the estuary. Most of the references cited merely list 

 foods found in the stomachs of various estuarine nekton. 



Generalized food webs are basically fueled by either a phytoplankton 

 source of energy or a detrital source. Recent advances in nektonic 

 food studies have stressed detritus as a food source for tropical 

 estuarine fishes, although some estuarine nekton depends solely on 

 phytoplankton. 



Most food studies have been done as an afterthought and not as part 

 of a carefully planned experiment. Few of the studies cited permit com- 

 parison with other areas; none contain adequate environmental informa- 

 tion. Some have gone into considerable detail, but these usually raise 

 more questions than they answer. (B.W.) 



Keywords: food webs, estuaries, fishes, marine invertebrates, 

 U.S. coastal regions 



III-E-27 



Chadwick, H.K., W. Heubach, and D. Daniel. 1972. Invertebrate animals 



and their environmental requirements. Pages 26-35 iji^ J.E. Skinner 



(compiler). Ecological studies of the Sacramento-San Joaquin estuary. 



California Department of Fish and Game, Delta Fish and Wildlife 



Protection Study Report No. 8. 



Zooplankton, Neomysis , and zoobenthos are discussed in this chapter 

 in terms of distribution and abundance and factors controlling abundance. 

 Of the zooplankton, the following types probably depend on phytoplankton 

 for food: protozoans, rotifers, and crustacean plankters. The crustacean 

 plankters, however, may also use organic detritus for food. 



Food habit studies of Neomysis are incomplete, but investigations thus 

 far have disclosed that mysid stomachs contain phytoplankton, detritus, 

 entomostracan parts, and, in some cases, entire rotifers. 



Benthic animals or zoobenthos are primarily invertebrates that live 

 in or on the bottom substrate of aquatic habitats. In the Sacramento- 

 San Joaquin estuary they are an important source of food for some fish 

 and for a number of waterfowl and shorebirds. (B.W.) 



Keywords: invertebrates, zooplankton, marine organisms, food habits, 

 California 



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