Influence of Turbid Inflows on Vertical Distribution of Larval Shad and Freshwater Drum

Tucker-trawl collections showed that behavior of larval shad Dorosoma spp. and freshwater drum Aplodinotus grunniens was altered by inflow of turbid water into Lake Texoma (Oklahoma-Texas) in two different years. During periods of increased turbidity, larval shad were concentrated in a reduced volume of water near the surface, and larval freshwater drum were distributed throughout the water column in contrast to their normal concentration near the bottom. In 1981 and 1982, greatest decline in abundance of larval shad came after zooplankton density fell below 100 per liter, and during or immediately following an extended period of high turbidity. Nutritional stress resulting from decline in zooplankton abundance and changes in larval-fish behavior during turbid conditions could be one important factor in population dynamics of shad in reservoirs.