Genetic Variation Between Lake Maurepas and Mississippi River Basin Fishes

K. Piller

Project Overview

The Lake Pontchartrain Basin harbors a distinctive and ever-changing fish community. In the last several years, low-rainfall conditions and subsequent increases in salinity in the basin have threatened the primary freshwater fish fauna in Lake Maurepas in the western portion of the basin.

Although the influx of water is aimed at restoring the wetlands around Lake Maurepas by providing freshwater to the system, it also may impact the ichthyofauna (fish) of the basin through homogenization of genetically distinctive stocks of fishes. This study offers the unique opportunity to use Mississippi River diversions as a model for the effects of homogenization on fish populations.

This study examines blue catfish (Ictalurus furcatus) and bluegill sunfish (Lepomis macrochirus). Tissue samples are collected from multiple fish populations from each basin. High-resolution nuclear loci (microsatellite loci), are used to quantify genetic divergence between Mississippi River and Lake Pontchartrain Basin populations.

Blue Catfish (Ictalurus furcatus):  Multiple independent data analyses clearly indicate that there is a high level of gene flow within and among populations of blue catfish in the Lake Pontchatrarin and Mississippi River basins.  Therefore, all populations examined can essentially be treated as one panmictic population.  Based on these indirect assessments of population structure it appears as though the impending Hope Canal diversion will not disrupt the genetic composition of blue catfish in these basins.

Bluegill Sunfish (Lepomis macrochirus): Preliminary analysis suggests some genetic difference between Lake Pontchatrarin and Mississippi River populations. Research is ongoing.