Data from: Hydrology controls recruitment of two invasive cyprinids: bigheaded carp reproduction in a navigable large river

In the Mississippi River Basin of North America, invasive bigheaded carp (silver carp Hypophthalmichthys molitrix and bighead carp H. nobilis, also referred to as Asian carp) have spread rapidly over the past several decades. In the Illinois River, an important tributary of the Upper Mississippi River, reproduction appears to be sporadic and frequently unsuccessful, yet bigheaded carp densities in this river are among the highest recorded on the continent. Understanding the causative factors behind erratic recruitment in this commercially-harvested invasive species is important for both limiting their spread and managing their harvest. We analyzed weekly catch records from 15 years of a standardized monitoring program to document the emergence of age-0 bigheaded carp in relation to environmental conditions. The appearance of age-0 fish was generally linked to hydrographic attributes, which probably serve as a cue for spawning. However, we found profound differences in the number of age-0 fish among years, which varied by as much as five orders of magnitude in successive years. The strong link between summer flooding and age-0 fish production we observed emphasizes the importance of understanding the hydrologic context in which sustained invasions occur. Despite evidence of sporadic recruitment, bigheaded carp populations in the Illinois River appear to be consistent or increasing because of particularly strong, episodic year classes.

在北美密西西比河流域，入侵性大头鲤（包括鲢鱼*Hypophthalmichthys molitrix*和鳙鱼*H. nobilis*，亦被称为亚洲鲤鱼）在过去数十年间快速扩散。作为密西西比河上游重要支流的伊利诺伊河，其大头鲤的繁殖活动看似零散且常以失败告终，但该流域的大头鲤种群密度却是北美大陆有记录以来最高的之一。解析这一兼具商业捕捞价值的入侵物种种群补充不稳定的成因，对于限制其扩散以及优化捕捞管理均具有重要意义。本研究依托一项为期15年的标准化监测项目的周度捕捞记录，探究了0龄大头鲤的出现与环境条件的关联。研究发现，0龄鱼的出现通常与水文特征相关，这类特征或可作为产卵行为的触发信号。然而，不同年份的0龄鱼数量存在显著差异，连续年份间的数量波动幅度最高可达五个数量级。本研究观测到夏季洪水与0龄鱼产量间存在强关联，这凸显了厘清持续入侵发生的水文背景的重要性。尽管存在繁殖补充零散的观测证据，但伊利诺伊河的大头鲤种群却保持稳定甚至有所增长，这得益于个别年份极强的阶段性种群补充事件。