Recent introduction of the planktonic calanoid copepod Sinocalanns doerrii (Centropagidae) from mainland China to the Sacramento-San Joaquin Estuary of California

The planktonic calanoid copepod, Sinocalanus doerrii, a nativeof the rivers of mainland China was found in 1978 in California'sSacramento-San Joaquin Estuary during routine plankton sampling.Previous plankton surveys in 1963 and from 1972 to the presentindicate that the introduction occurred a relativery short timebefore specimens were first caught. The most probable mode ofintroduction is ballast water from Japanese freighters previouslydocking in China. S. doerrii became abundant in the Sacramentoand San Joaquin Rivers in 1979 and may be regarded as well established.Its impact on the native plankton is as yet unknown. ⁴Present address: Department of Biological Science, FloridaState University, Tallahassee, FL 32306, USA. ⁵Present address: 5 Hemingway Street, Branford, CT 06405, USA.