Seasonal and Areal Comparisons of Fish Diversity Indexes at A Hot-Water Discharge in Galveston Bay, Texas

Trawl and hydrological samples were taken at 11 stations once each month Jan 1968 through Dec 1969 in an area of Galveston Bay receiving a discharge of heated water from the P.H.Robinson Generating Station. The stations were grouped by location into 3 areas: (1) an up-bay control area, (2) the discharge area and (3) a down-bay control area. The data from stations in each of the 3 areas were pooled and 3 diversity indices, the Shannon-Weaver index (H), evenness (J) and species richness (D), were calculated for each monthly sample. Analysis of all indices showed marked seasonal differences. No significant differences in overall diversity (H) or evenness indices were observed between years or areas. The spp richness index for 1968 was significantly higher than that for 1969 and the discharge area had significantly greater spp richness than either control area. The greater spp richness in the discharge area may have been related to sample size. In the discharge area, all indices declined when mean surface water temp was > 35{degree}C.