Habitat Use, Diet, and Population Structure of Adult and Juvenile Paddlefish in the Lower Alabama River

We quantified habitat use, diet, and population characteristics of paddlefish Polyodon spathula in the lower Alabama River, Alabama, in an effort to determine whether juveniles and adults differ in their seasonal use of three types of habitats (oxbow lakes, backwater areas, and channel areas) and to identify differences in population characteristics between fish from the Alabama River and those from other drainage systems. Both juveniles and adults used backwater and channel areas. Paddlefish used backwater areas primarily during summer and fall and channel habitats during winter and spring. Juvenile paddlefish that were present in backwater areas migrated with prespawn adults, whereas juveniles in the oxbow habitat did not. Juvenile paddlefish used oxbow lakes as nursery areas, remaining there until sexual maturity. Paddlefish in the lower Alabama River had shorter life spans than those previously studied further north, suggesting a latitudinal gradient in fish survival. Although fecundity rates were higher, in part compensating for their shorter life span, growth rates were lower than observed elsewhere. Slow growth may result from inhabiting areas where water is warmer than optimal for feeding. However, part of the apparent difference in growth rates may be due to problems in aging paddlefish in previous studies. Paddlefish consumed primarily copepods and cladocerans when available; however, ephemeropteran nymphs were consumed heavily in the channel habitat during winter and spring.