Ch. 3— Wetland Values and the Importance of Wetlands to Man • 59 



Table 9.— The 15 Most Important Fish and Shellfish Harvested by U.S. Fisheries in 1980 



Thousands of dollars Thousands of pounds 



Nonestuarine Estuarine Nonestuarine Estuarine 



Shrimp (several species, all coasts) ... — $ 402,697 — 339,707 



Salmon (5 ipecies) — 532,277 — 613,811 



Tuna (6 species) $233,125 — 399,432 — 



King crab 168,694 — 185,624 — 



Menhaden (Atlantic and Gulf) — 112,012 — 2,496,649 



Sea scallops 1 10,429 — 28,752 — 



Flounders (several species, all coasts) . — 82,488 — 216,920 



American lobster 75,233 — 36,952 — 



Oyster — 70,075 — 49,081 



Snovi/, or tanner crab 55,161 — 121,674 — 



Sea herring (Atlantic and Pacific) 44,955 — 291,069 — 



Hard clam — 44,068 — 13,370 



Blue crab — 55,167 — 163,206 



Atlantic cod 31,883 — 118,245 — 



Dungeness crab — 21,613 — 38,025 



Total $719,480 $1,120,397 1,181,748 3,930,769 



Percent 39% 61% 23% 77% 



SOURCE: National Marine Fisheries Service, "Fisheries of the United States, 1980," Current Fishery Statistics No. 8100, 1981. 



lion lbs of estuarine fish and shellfish species were 

 landed by U.S. commercial fishermen in 1980. This 

 represented 63 percent of total U.S. commercial 

 landings at U.S. ports, with a dockside value of 

 $1.15 billion, 51.5 percent of the value of the total 

 catch. The retail value of the estuarine-related catch 

 is more speculative. 



Factors Affecting Production of Plant Mate- 

 rial. — The production of plant material in wedands 

 generally is high relative to other upland ecosys- 

 tems, such as grasslands (table 10), largely because 

 of the flux of nutrients and water through wetlands 

 (75). In general, production of plant material will 

 be greatest in wetlands of flowing or regularly fluc- 

 tuating water and lowest in Stillwater wetlands (un- 

 less enriched by nutrients) (14). Approximately 15 

 percent or less of the annual plant growth of coastal 

 marshes* is harvested by direct feeding by macro- 

 invertebrates such as fiddler crabs, snails, amphi- 

 pods, and polychaete worms (49). After the grow- 

 ing season, most standing plant m.aterial on 

 marshes dies. 



Up to 70 percent of the net primary productivi- 

 ty of coastal wetlands may be exported from the 

 wetland to open-water areas (49). The amount ex- 

 ported will vary — in the "high marsh," only 10 



percent may be exported, while areas adjacent to 

 the water's edge may export much more. In some 

 cases, there may be no net export. Any detrital par- 

 ticles exported from the marsh rapidly are colonized 

 by bacteria, fungi, and other micro-organisms 

 which increase the concentration of protein and fat- 

 ty acid content, enhancing caloric value. These mi- 

 crobes also adsorb dissolved organic compounds 

 from the surrounding water. As a result, the orig- 

 inal plant material is transformed into a nutritious 

 food source for filter feeders."" 



'This discussion pertains to coastal marshes. Limited research in- 

 dicates that dissolved organic compounds and decaying plant material 

 are exported from inland wetlands at a greater rate than from uplands 

 of equivalent area. 



"Sather and Smith, op. cit. 



Table 10.— Wetland Plant Productivity 

 (metric tons per hectare per year) 



Range 

 Coastal: 



Salt marshes (aboveground only): 



Louisiana and Georgia 22 



North Atlantic 4-7 



Pacific coast 3-19 



Freshw/ater tidal wetlands 



(above and below ground) 13-16 



Inland: 



Freshwater marshes (above and below ground): 



Sedge-dominated marshes 9-12 



Cattail marshes 20-34 



Reed 15-27 



Bogs (above and below ground) 4-14 



Wooded swamps 7-14 



SOURCE: Wetland Functions and Values: The State of Our Understanding, P. E. 

 Greeson, J. R, Clark and J, E Clark (eds.) (Minneapolis, Minn.: American 

 Water Resources Association. 1979), pp 146-161, 



