Effects of Hurricane Katrina on freshwater fish assemblages in a small coastal tributary of Lake Pontchartrain, Louisiana

Martin O'Connell, University of New Orleans


Hurricane Katrina struck southeastern Louisiana on 29 August 2005 and thereby created an opportunity to examine the effects of a catastrophic storm on fish assemblages in a coastal stream. Bayou Lacombe is a small (46.1 river kilometers), primarily freshwater stream that drains into the northeastern portion of Lake Pontchartrain, a large oligohaline estuary located north of New Orleans. In summer 2005 (prior to the hurricane), three upstream and three downstream reaches of Bayou Lacombe were surveyed by electrofishing. These same six reaches were resurveyed in the summer of 2006 to assess the effects of the hurricane on fish assemblages. There were significant changes in fish assemblages at the downstream and upstream reaches. At the downstream reaches, centrarchid species such as bluegill Lepomis macrochirus, warmouth L. gulosus, and redspotted sunfish L. miniatus increased in abundance after the hurricane, as did inland silverside Menidia beryllina and striped mullet Mugil cephalus, both estuarine-dependent species. At the upstream reaches, longear sunfish L. megalotis decreased after the hurricane and weed shiners Notropis texanus, goldstriped darters Etheostoma parvipinne, and warmouth were absent from posthurricane samples. Principal components and BEST analyses showed that differences in dissolved oxygen between years were related to fish assemblage changes in the upstream reaches. Salinity and temperature were associated with fish assemblage changes in the downstream reaches. Similar significant changes could occur in other coastal streams prone to increased hurricane activity.