Effects of Dams on Migratory Fishes in the Alabama River: Laying the Groundwork for Restoration

Abstract

To understand the effects of dams on migratory fishes in the Alabama River Basin and support conservation of these species, I conducted studies on the past, present, and potential future of the system. The first study was to describe the ranges of migratory fish in the Mobile River Basin prior to the construction of dams (Pre-1890). Given the lack of scientific data from this period, I used archived newspapers and other historical sources to find occurrences of six imperiled migratory fish species and show how their ranges have declined over time. The second study was to track migrating Paddlefish after translocating them above a dam impeding their migration. I sought to know whether fish would be able to navigate the reservoir upstream and find potential spawning habitat if passage at the dam was improved. The majority of fish surviving translocation made upstream movements through the reservoir, but their survival during passage back downstream through the dam may have been limited. Finally, I conducted a simulation study to test how improving fish passage at dams on the Alabama River might affect a fragmented metapopulation of Paddlefish in the future. I programmed an agent-based model and explored the consequences of various parameterizations on the likelihood of population segment extirpation. At low levels of downstream entrainment, and levels of natural mortality slightly higher than estimated for the metapopulation, persistence of all segments was possible across diverse upstream passage scenarios. However, increasing passage led to more positive effects, which is promising for future mitigation efforts at the dams.