include annual shellfish harvests of 

 2.2 million pounds. So far only 

 parts of the upper reaches and some 

 tributaries of the Guadalupe-San An- 

 tonio river systems have been im- 

 pounded, but some major reservoirs 

 have been proposed downstream. 



Mission-Aransas And 

 Nueces (Corpus-Christi) 



The Mission-Aransas and Nueces 

 (Corpus-Christi) estuaries both have 

 median total annual inflows of only 

 half the volume of the estuary. 

 These estuaries make up 17 percent 

 of the estuarine area in Texas, and 

 accounted for 20, 9, 7 and percent 

 of the estuarine harvests of brown 

 shrimp, white shrimp, blue crabs, 

 and oysters, respectively, from 

 1962 through 1977. 



Parker (1955) noted years ago 

 the adverse impacts of high salinity 

 on white shrimp and oysters in the 

 Mission-Aransas estuary. More re- 

 cently, Chapman (1973:249) observed, 

 "The diversion and consumptive use 

 of tributary fresh water received by 

 the southwestern Texas estuaries al- 

 ready has reached critical propor- 

 tions. Tributary flow to Corpus 

 Christi Bay, Texas, has been re- 

 duced to the point where the estu- 

 ary now becomes hypersaline most sum- 

 mers through excessive evaporation, 

 to the detriment of fishery re- 

 sources." The Texas Department of Wa- 

 ter Resources (1979e) predicted 

 that the fisheries could be main- 

 tained, and even increased by over 

 a fourth, with an amount just slight- 

 ly greater than the historical medi- 

 an annual inflows. However, Cope- 

 land (1966:1836) noted that, in 

 these bays "The minimum freshwater 

 contribution required to maintain 



the present commercial fisheries is 

 not reached in some years." A major 

 reservoir, Choke Canyon, now under 

 construction in the principal drain- 

 age basin, the Nueces, will increase 

 the frequency of insufficient in- 

 flows when its yield begins to be 

 utilized. 



Laguna Madre 



The Laguna Madre, the southern- 

 most estuarine system, has a median 

 total annual inflow of only 0.4 times 

 the estuarine volume (0.2 in the up- 

 per and 0.5 in the lower Laguna Ma- 

 dre; and shrimp fishing, except for 

 bait, is not permitted. Sciaenid 

 fish, which are fished both commer- 

 cially and recreationally, are abun- 

 dant in the upper Laguna Madre (Sim- 

 mons 1957), Baffin and Alazan Bays, 

 and the lower Laguna Madre (Breuer 

 1957; 1962). Stokes (1974) found 

 that postlarval and juvenile brown 

 shrimp were abundant in over 40 per- 

 cent of the lower Laguna Madre, 

 whereas white shrimp were abundant 

 in less that 5 percent of the estu- 

 ary. This part of the estuary pri- 

 marily was where freshwater flows, 

 or return flows, enter. 



Harvests of brown shrimp in 

 Texas estuaries represent only ap- 

 proximately 5 percent by weight of 

 brown shrimp catches along the Tex- 

 as coast (National Marine Fisheries 

 Service 1962-1977b); therefore, 

 the bay catches referred to above 

 may be poor indicators even of rel- 

 ative population. Correlation-re- 

 gression analyses indicated that 

 offshore shrimp harvests for all 

 three species, white, brown, and 

 pink, are positively correlated with 

 spring (April-June) inflow and nega- 

 tively correlated with winter (Janu- 

 ary-March) and summer (July-August) 



417 



