Assessment of larval fish entrainment at Plant Barry Steam Electric Generating Facility on the Mobile River, Alabama

Abstract

This study examined larval fish entrainment at Plant Barry Steam Electric Generating Facility near Mobile, Alabama with both short-term intensive (17-21 May 2004) sampling and a long-term (September 2004June 2005) collection effort. The overall objective was to determine the best site for entrainment sampling at Plant Barry. Other objectives included quantifying the taxonomic composition and density of larval fish families being entrained. Larval fish collections in the intensive study were performed in the intake canal, the Mobile River, the discharge tunnels, and a condenser tap inside the plant. Larval fish were captured by passing 100 m3 of water through plankton nets (330µm mesh). All collected larval fish were transported to the laboratory where they were sorted, identified, and counted. The long-term larval fish collections were performed in the same manner using the unit 2A condenser tap inside Plant Barry. Both site (pair-wise) and diurnal statistical comparisons were performed for the intensive collections based on total numbers and larval fish densities by family. Major families collected throughout this portion of the study included Clupeidae, Cyprinidae, Centrarchidae, and Sciaenidae. Overall, the intake canal generally provided more liberal assessments of larval fish entrainment, while samples inside Plant Barry gave more conservative estimates. No one site could be labeled as best for the assessment of larval fish entrainment due to factors such as power plant effects and larval fish stratification. Intake canal and Mobile River transect comparisons showed that each larval fish family was subject to introduction into the intake canal by the hydraulic zone of influence (HZI) and Mobile River. The HZI is the water drawn from the Mobile River into the intake canal due to the intake velocity of the power plant. For each larval fish family, at least one site was not statistically different to the densities in the intake canal, suggesting that the HZI had some effect on larval fish introduction into the intake canal. Long-term collections of larval fish entrained by Plant Barry contained fish from the families of Clupeidae, Cyprinidae, Catostomidae, Centrarchidae, and Sciaenidae. Peak entrainment of larval fish occurred in April, with Sciaenidae showing a peak in May. Knowledge of the spawning characteristics of these fish families is important when performing future annual entrainment studies at Plant Barry in order to assess both the maximum and minimum entrainment values per year.