Evidence of reproduction by exotic grass carp in the Red and Washita rivers, Oklahoma

摘要

Grass carp, Ctenopharyngodon idella, is an invasive cyprinid that has been stocked throughout the USA for biological control of aquatic macrophytes. Natural reproduction was expected to be limited in the USA due to a lack of long, unimpounded rivers with sufficient flow needed for reproduction. However, natural reproduction has been documented in the Mississippi, Missouri, and Trinity (Texas) rivers. In 2 years of shoreline seining in Lake Texoma (Oklahoma-Texas), we found evidence of natural reproduction by grass carp in the Red and Washita rivers. In 1999 and 2000, we collected 79 juvenile grass carp from 6 of 41 sites sampled in the reservoir. Juvenile length ranged from 15.2 to 60.0 mm total length, with 2 apparent size groups (modes of 18 and 41 mm). Most grass carp juveniles were collected in 2000 in the upper Washita River arm of Lake Texoma. We hypothesize that tributary conditions and littoral habitats in Lake Texoma influenced grass carp abundance and survival.