Population dynamics of non-native Yellow Bass in Iowa’s natural lakes region

Non-native Yellow Bass Morone mississippiensis have recently expanded their range in Iowa’s glacial natural lakes since their initial introductions in Clear Lake, Iowa circa 1930. Little is known regarding Yellow Bass population dynamics inhabiting natural lakes of varying complexity, thus limiting management options for the species. This study aimed to assess and compare age and size structure, condition, growth, and mortality of Yellow Bass collected from ten natural lakes in Iowa between 2017 and 2022. We also evaluated the effect of Yellow Bass relative abundance and lake size on Yellow Bass size structure, growth, and condition. Our results indicate substantial variation in Yellow Bass population parameters among and within natural lakes of different sizes and infestation periods; however, some general trends were observed. Lakes that were recently infested typically had higher Yellow Bass growth, size structure, and mortality than those with established populations. Likewise, lowest mortality rates were observed in lakes with the poorest growth, poorest condition, and poorest size structure, yet densities in these lakes differed considerably. Natural lakes ≥394 ha had better growth, condition, and size distribution than smaller lakes, regardless of the year they were infested. This study provides insight into the population dynamics of non-native Yellow Bass in natural lakes and identified several population responses they may display post-infestation. Our findings reiterate the importance for fisheries managers to perform routine fisheries surveys in lakes to document the expansion and monitor the population dynamics of Yellow Bass.