Effects of American Water Willow Establishment on Density, Growth, Diet, and Condition of Age-0 Largemouth Bass in Kansas Reservoirs

Many Kansas reservoirs are currently experiencing decreased sport fish production as a result of the typical aging processes that occur in impounded systems. American water willow Justicia americana was planted in three Kansas reservoirs (>1,800 ha) for littoral zone habitat enhancement to mitigate sport fish losses and increase the recruitment of age-0 largemouth bass Micropterus salmoides. We investigated whether the density, growth, condition, and diet of age-0 largemouth bass in coves with water willow differed from coves without water willow in these reservoirs. Samples of largemouth bass were collected from 2001 to 2004 in June, July, and August. We found a consistent pattern among reservoirs and sample years; coves with water willow had significantly greater densities of age-0 largemouth bass than control coves, but no significant differences were found in growth, condition, or diet. Water willow beds appeared to buffer wave action, trapping fine sediments and floating debris, which significantly increased the overall habitat complexity. The additional organic material may have augmented littoral productivity, supporting the higher densities without physiologically hindering the age-0 largemouth bass. Overall, our study suggests that water willow establishment is an effective means of enhancing littoral nursery habitat for age-0 largemouth bass.