Exciting Times for Fisheries Research in the Atchafalaya River Basin: Hurricanes, Missing Fish, and Crawfish

By Mike Kaller, Assistant Professor of Research

Louisiana is fortunate to have one of the world’s great bottomland hardwood swamps in the Atchafalaya River Basin (ARB).  Anglers, hunters, and bird and wildlife enthusiasts, as well as timber, oil, gas, and commercial fishers all derive great benefits from the ARB.  Since 2000, RNR faculty have had long-term fish and water quality monitoring projects at various locations in the ARB, including Henderson Lake, Buffalo Cove, and Flat Lake.  Because of the consistency of data collection, these projects have permitted assessment of water management projects such as the Bayou Postillion dredging project, and catastrophic events such as Hurricanes Katrina and Gustav.

Research efforts have primarily focused on fish communities and water quality.  The ARB undergoes an annual cycle of flooding, pooling on the floodplain when floodwaters rise, and eventual draining as flood stages decline in the Atchafalaya and Mississippi Rivers.  Because of levee and canal construction and invasions by several exotic plants, water flowing onto the inundated floodplain tends to pool, which leads to loss of dissolved oxygen in the water and stress or death of fishes.  Recent research has suggested that increasing water movement would be an effective means of enhancing water quality and improving fish populations.  The U.S. Army Corps of Engineers and Louisiana Department of Natural Resources are implementing projects to address poor water flow in ARB, and SRNR researchers will continue to be involved with assessing the effectiveness of these projects. 

These long-term data sets have also allowed RNR faculty to investigate the impacts of hurricanes on the ARB fish comunity.  In 1992, Hurricane Andrew killed thousands of fish, but scientists were unable to identify how the kills occurred because data about water conditions prior to the hurricane were not readily available.  At the time, biologists speculated that either toxic gases released from disturbed bottom sediments or rapid losses of dissolved oxygen killed the fish.  When hurricanes impacted the ARB in 2005 and 2008, reliable and consistent data were available before and after the storms.  Research associates Alex Perret and Raynie Harlan have been investigating hurricane impacts on fish and water quality.  Powerful hurricanes like Katrina appear to substantially reduce the number of largemouth bass, sunfish, and catfish inhabiting the ARB.  Preliminary results suggest that storm surge and heavy rains lead to water pooling on the floodplain, which quickly becomes deoxygenated and possibly leads to fish kills. 

Graduate students Thorpe Halloran and Chris Bonvillain also have been active in the ARB during the last few years.  Thorpe is the third student to investigate fish reproduction in the ARB.  Over 100 species of fish live in the Atchafalaya River and on its floodplain, but spawning and larval-rearing habitats are known for less than half of them.  He has expanded on previous research to determine whether prey or physical conditions are more important in determining larval fish abundance. Similarly, crawfish distribution in the floodplain and year-to-year abundance fluctuations are difficult to explain. Chris is combining field samples and laboratory experiments to determine if physiological limitations may explain the abundance and distribution of crawfish.  Recreational and commercial fisheries and crawfishing are economically and culturally important to Louisiana.  Insights from these ongoing projects will greatly enhance our ability to explain the abundance and distribution of fishes and crawfish in the ARB, and may provide important information for the development of future management programs.