Spatial and Temporal Patterns of Larval Asian Carp Production in Illinois and Wabash River Tributaries

Asian carps are non-native fishes that have deleterious effects on the ecosystems they invade. Because of their destructive nature, fisheries managers are devoting large amounts of effort to limit the spread of these fishes. A better understanding of factors that influence spatial and temporal patterns of Asian carp reproduction can help fisheries professionals better manage these species. To examine abiotic factors that influence spatial and temporal patterns of reproduction, we used drift nets and larval push nets in three tributaries of both the Illinois and Wabash Rivers. Relative abundances of larvae were compared for all Hypopthalmichthyes (Silver and Bighead Carp) and Grass Carp. Further, we used regression analyses to determine the strength of the relationship between egg and larvae abundances with various abiotic factors of both the tributary and main (Illinois or Wabash) river. In total, 1,239 Hypopthalmichthyes and 289 Grass Carp were collected from 4 of 6 sampled tributaries. Most (99% of Hypopthalmichthyes and 99% of Grass Carp) larval Asian carps were sampled in Wabash River tributaries and of those, the Little Wabash River was the most productive (83% of Hypopthalmichthyes and 100% of Grass Carp). Catches of larvae were positively related to discharge, particularly a rising hydrograph. Future research will include using genetic techniques to determine if distinct populations of Asian carps are using particular sites to spawn, whether in certain tributaries or in the main stem rivers. We expect this research to improve our understanding of Asian carp reproduction and help fisheries professionals better mediate their spread.