D. Site Studies 



IV-D-1 



Hedgpeth, J.W. 1967. Ecological aspects of the Laguna Madre, a hyper- 

 saline estuary. Pages 408-419 in^ G.H. Lauff, ed.. Estuaries. American 

 Association for the Advancement of Science, Washington, D.C. 



The Laguna Madre of Texas is a series of coastal lagoons, consisting 

 of a long narrow outer lagoon separated from the Gulf of Mexico by 

 Padre Island, and divided into northern and southern parts by extensive, 

 barren flats, and an inner tributary, Baffin Bay, extending westward 

 like an elbow from the lower part of the main Laguna. 



There is an abundant and varied fish fauna in the various parts 

 of the Laguna. Among the resident species in the Laguna Madre are 

 the tenpounder or skipjack ( Elops saurus ), anchovies ( Anchoa spp.), 

 three species of cyprinodontids ( Fundulus similis , F. grandis , and 

 Cyprinodon variegatus) , the s i 1 versides ( Menidia beryl Tina peninsulae ) , 

 mullet ( Mugil cephalus ), the spotted sea trout ( Cynoscion nebulosus ), 

 and the black drum ( Pogonias cromis ). These species are known to 

 spawn in the Laguna, and most of them are winter or early spring 

 spawners. While complete data are lacking, it appears that most of 

 these species do not spawn in concentrations of salinity in excess 

 of 45 parts per thousand (ppt ). Some of them, however, probably 

 spawn in higher salinities; an atherinid ( Atherinops affinis affinis ) 

 can spawn in concentrations of 72 ppt, but the young die within four 

 months. Many other species of fish spend considerable time in the 

 Laguna, but do not spawn there and usually leave in summer during 

 temperature and salinity rises. Other fish are occasional visitors. 

 More than 70 species of fishes occur in the upper Laguna Madre. Two 

 of the most important species in terms of species mass and represen- 

 tation in both sports and commercial fisheries are the redfish, 

 Sciaenops ocellata , and the black drum, Pogonias cromis . The redfish 

 IS not a pe»-nianent resident, and does not spawn in the Laguna , while 

 the black drum does. The black drum also seems to withstand higher 

 temperatures and salinities, although older fish tend to become 

 deformed and blind in the highest salinities. 



The living invertebrates of the Laguna have not been so thoroughly 

 studied as the fishes. Crustaceans of several species are abundant, 

 and make up a significant part of the food for several species of 

 fishes, especially the redfish. Young blue crab, Callinectes sapidus , 

 and the small mud crab, Neopanope texana , are the important crabs. 

 Young penaeids, especially Penaeus aztecus , and the small resident 

 grass shrimp, Palaemonetes intermedius , are the most important shrimp. 

 Ac art i a tonsa is apparently the dominant copepod of the Laguna waters, 

 and feeds on some reddish submicroscopic plankters. It is important 

 as a food item for small fish. 



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