Cordell, J. R., Bollens, S. M., Draheim, R., and Sytsma, M. 2008. Asian copepods on the move: recent invasions in the Columbia–Snake River system, USA. – ICES Journal of Marine Science, 65: 753–758. Nine Asian copepod species have been introduced into the Northeast Pacific, seven of which are largely confined to the San Francisco estuary. However, several of these copepods recently invaded the Columbia–Snake River system in Washington state, USA. In addition to the calanoid copepod Pseudodiaptomus inopinus, which appeared in the 1980s, the Columbia River now has populations of the calanoids Pseudodiaptomus forbesi and Sinocalanus doerrii, and the cyclopoid copepod Limnoithona tetraspina. Sampling in the Columbia–Snake River system in 2005 and 2006 indicated that (i) newer invaders may have displaced the previously introduced P. inopinus; (ii) P. forbesi had moved upstream into the first five reservoirs in the system; (iii) the other species occurred only in the tidal regions of the lower river; (iv) P. forbesi dominates the late summer holoplankton in the lower river and estuary; and (v) P. forbesi is relatively rare, and the holoplankton is dominated by native species in upstream free-flowing segments of the Columbia River and in reservoirs of the Snake River. Zooplankton samples from ships in Puget Sound suggest that ballast water from California is a major source of the introduced copepods and that the Columbia River itself may be a new source of ballast-introduced copepods.

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Estuaries play an important role as nurseries and migration corridors for Chinook salmon and other fishes. The invasive New Zealand mudsnail,

We report the first occurrence in the Pacific Northwest, USA, of the harpacticoid copepod genus Harpacticella (Family Harpacticidae), which has previously been recorded only from Asia and from an atoll in the Indian Ocean. Harpacticella paradoxa (Brehm, 1924) is native to streams, lakes and estuaries in Japan and China. H. paradoxa was found in plankton samples taken in 2000 and 2004 from 2 geographically separated estuaries (Samish and Klamath River Estuaries, USA) at salinities ranging from 0 to 15 psu. H. paradoxa was also found associated with plants sampled in 2006 from a freshwater reservoir in the Columbia River, Washington State, USA. Because the genus Harpacticella has previously been found only in Asia and the Indian Ocean; is probably easily transported on ship hulls or in ballast; and appears to have a disjunct regional distribution, we regard it as a probable introduced species to North America.

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