Several small bivalves are common in various parts of the Laguna, 

 and constitute a major element in the diet of the black drum. The 

 most common species are Anomalocardia cuneimeris and Mulinia lateralis ; 

 evidently these occur in extensive beds although there is no clear 

 information on the locations of these beds or the density of molluscs 

 per unit area. 



In the Laguna Madre there are at least 25 species of animals that 

 persist or withstand concentrations of 75-80 ppt salinity. Some of 

 these also occur in salinities as low as 15 ppt. Data are provided 

 showing the occurrence of certain metazoa in salinities of 45 ppt 

 and above. (H.D.) 



Keywords: estuaries, salinity, fish, invertebrates, Texas 



IV-D-2 



Hellier, T.R. 1962. Fish production and biomass studies in relation to 

 photosynthesis in the Laguna Madre of Texas. Publications of the 

 Institute of Marine Science, University of Texas 8:1-22. 



The rate of growth of populations of animal consumers depends to a 

 considerable extent on the rate of food supply derived from photo- 

 synthetic production of plant material either within or imported 

 into the community. Yet few studies directly relate fish production 

 to plant production. In the present study, an effort has been made 

 to relate fish production to gross plant production in a shallow, 

 frequently hypersaline coastal bay, the Upper Laguna Madre of Texas. 

 The Upper Laguna Madre is located on the Texas Gulf Coast immediately 

 south of Corpus Christi Bay, and is separated from the Gulf of 

 Mexico by a narrow barrier island. Padre Island. 



The northern portion of the bay is very shallow, ranging from one 

 to three feet deep in the zone extending for 13 miles south of the 

 causeway, where there is a natural basin approximately five feet 

 deep. This basin delimits the southern boundary of the present study 

 area. The shallow portion of the Upper Laguna Madre was 

 covered with a dense growth of shoalgrass ( Diplanthera wrightii ) 

 and widgeongrass ( Ruppia maritima ) . Acetabularia crenulata was 

 frequently encountered in the area, though it was never abundant. 



Biomass estimates of the animal species present were determined 

 with a new population sampling device, the drop-net quadrat. The 

 principle of this method is to isolate instantaneously a segment of 

 the study area with its natural fish population, and by extrapolation 

 determine the approximate density of the fish population of the area. 

 Twenty-nine samples were taken over a 1^-month period from March 1958 

 to August 1959. 



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