Fishery survey of Cedar Lakes and the Brazos and San Bernard River estuaries.
Johnson, R.B., Jr.
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A fishery study of Cedar Lakes and the lower parts of the Brazos and San Bernard Rivers, Brazoria County, Texas, was conducted in February 1973 to January 1975. Samples were collected at 17 stations each month to determine hydrological conditions and occurrence of estuarine organisms. Salinity, temperature, dissolved oxygen values, pH values and turbidity were determined in surface and bottom water samples. An otter trawl was used to sample nekton. Benthos was sampled quarterly at the 17 stations with an Ekman dredge. Samples were collected at four stations monthly after December 1973 with a minnow seine. Area and station descriptions are presented. Additional biological samples were collected in back bays, bayous and sloughs with the otter trawl and minnow seine. Combined with samples from several regular stations, information was used to map nursery habitat of 10 species of fish and crustaceans of economic value. Salinity was affected by river and stream discharge, tidal intrusion from the Gulf of Mexico, and industrial waste brine and cooling water discharges. The salinity range was zero to 32.2 ppt. Water temperature ranged from 8.8 to 35.1C, highest values occurring near a cooling water discharge in the Brazos River. Dissolved oxygen values were highest in winter and lowest in summer. Values less than 3.0 ppm were recorded in the Brazos and San Bernard Rivers. Effects of pollution are discussed. pH values were within the range of most natural waters, ranging from pH 6.4 to 8.9 Turbidity was affected by river discharge. Values exceeded 395 JTU in parts of the Brazos River 11 months of the study. Of 146 species of fish and invertebrates observed or caught in the study area, 35 were marine species which contribute to Texas recreational and commercial fisheries. An annotated checklist is presented. Cedar Lakes, Cow Troop Lake, Cedar Lake Bayou, Pelican Lake, McNeal Lake, McNeal Bayou, Jones Lake, Jones Creek, Old Reservoir, Bryan Lake and the lower 18.4 km of the San Bernard River are vital fisheries habitats. Pollution in the lower Brazos River has eliminated 9.8 to 211.1 km (depending upon weather conditions) of stream bottom from substantial fisheries production.