shellfish in 1967. Two-thirds of this total value, or approximately 

 $300 million, can be considered derived from estuarine-dependent species. 



The future economic value of the estuarine-dependent species for the 

 U.S. comnercial fishing industry will depend upon three major forces 

 influencing trends: (1) The shifting market demand for fishery products 

 in the U.S.; (2) the state of the commercial fishing industry on a world- 

 wide basis; and (3) the compatibility between evolving conditions in the 

 U.S. estuaries arW the production of adequate fishery stocks. 



The author discusses market demand for fish products including 

 industrial and edible fish products. Trends in the world fisheries 

 in relation to production costs and world demand is also covered. 



Estuarine-dependent species are divided and discussed in four 

 groups: (1) truly estuarine species, (2) anadromous and catadromous 

 species, (3) seasonally estuarine species, and (4) marine species 

 using estuaries as a nursery. 



Estuarine dependence of shrimp, menhaden, and oysters is also 

 discussed in detail. (H.D.) 



Keywords: estuaries, commercial fishes, nursery areas, fisheries 

 resources, U.S. coastal regions 



IV-B-8 



Cronin, L.E., and A.J. Mansueti , 1971. The biology of the estuary. 

 Pages 14-39 in_ P. A. Douglas and R.H. Stroud, eds., A symposium on 

 the biological significance of estuaries. Sport Fishing Institute, 

 Washington, D.C. 



Estuaries are defined as semi -enclosed booies of water that have free 

 connections with the open sea and within which sea water is measurably 

 diluted by fresh water from land drainage. The nearly 900 estuaries 

 along the coasts of the United States vary considerably. 



Some physical, chemical, and geological characteristics of estuaries 

 are discussed, including those characteristics that appear to be 

 common to many estuaries. Salinity, river flow, tidal movements, and 

 the chemical activity of elements and compounds are mentioned. 



The biological patterns of estuaries are discussed in detail: bacteria,^ 

 phytoplankton, zooplankton, benthos, and fishes. Fishes, in particular, 

 use estuarine waters in any or all of these ways--as spawning grounds, 

 nursery area, or feeding grounds. 



153 



