often greatly affected the general ability of the estuary 

 to offer the diverse range of habitats that allow a wide 

 range of organisms to thrive. Major alterations 

 affecting water-mass exchanges between the estuary 

 and the Gulf (and therefore the response of water 

 levels in the Nueces Estuary and Delta) include 

 alterations of the Nueces River channel, oyster shell 

 mining and the excavation of shipping channels, barrier 

 structures and artificial passes. The primary alteration 

 affecting salinity concentrations in the estuary and delta 

 is reduced freshwater inflows from to a combination of 

 dam construction and water extraction for agriculture, 

 industry and municipal uses. 



Data records do not exist to accurately document all of 

 the resulting alterations to the ecology of the Nueces 

 Estuary and Delta over the past century. However, it 

 is generally agreed that the combined effect of these 

 activities has resulted in an estuary and delta with 



higher salt concentrations in the soils and water, 

 channelized flow that reduced flooding by freshwater 

 overflow and tides, species shifts to more salt tolerant 

 forms and probably reductions in the total number and 

 biomass of plants and animals. The most notable and 

 evident changes have been reductions in oyster and 

 shrimp harvests (Montagna et al. 1998), each of which 

 requires a low salinity regime at some point in their life 

 cycle (Moffet 1970). With few exceptions (e.g., the 

 monitoring work conducted by the Texas Parks and 

 Wildlife Department in Nueces Bay), available data has 

 been primarily derived from subjective comparisons of 

 historical sources with present conditions, inferences 

 drawn from similar ecosystems, which have endured 

 comparable change processes, and direct observations 

 from recent monitoring activities. 



Chapter Tmo ♦ 2-19 



