Seasonal and areal comparisons of fish diversity indices at a hot-water discharge in Galveston Bay, Texas.

Trawl and hydrological samples were taken at 11 stations once each month from Jan. 1968-Dec. 1969 in an area of Galveston Bay (USA) receiving a discharge of heated water from the P.H. Robinson (J) and species richness (D), were calculated for each monthly sample. Analysis of all indices showed marked season differences. No significant differences in overall diversity (H) or evenness indices were observed between years or areas. The species richness index for 1968 was significantly higher than that for 1969 and the discharge area had significantly greater species richness than either control area. The greater species richness in the discharge area may have related to sample size. In the discharge area, all indices declined when mean surface water temperature was above 35 C.