Manayunkia speciosa Leidy is a freshwater polychaete that is widely distributed in coastal areas of the United States and Canada. Relatively little is known about the ecology of this species. However, the discovery that M. speciosa plays an obligate role in the life cycle of two parasites (Ceratomyxa shasta Noble and Parvicapsula minibicornis Kent) that can cause substantial mortalities in juvenile Pacific salmon (Oncorhynchus spp.) has sparked an interest in the ecology of this polychaete. Salmon of the Klamath River basin, California-Oregon, have experienced particularly high mortalities due to the parasites and management agencies in the region are actively seeking strategies to reduce loss of salmon due to the parasites. One strategy that has been developed is the use of flow manipulations to dislodge the polychaete from areas in which it is found in the Klamath River. The purpose of this study was: 1) to characterize invertebrate assemblages associated with M. speciosa to look for drivers of polychaete distribution, 2) to experimentally determine flow forces (shear stress) required to dislodge polychaetes from substrates on which they are found in the Klamath River, and 3) to compare experimentally determined shear stresses with those found in typical macrohabitats containing M. speciosa. Results from the invertebrate study showed that M. speciosa occurs on stable substrates in areas of high invertebrate diversity, including invertebrates that are marine relicts. Polychaete tenacity was dependent on both flow velocity and substrate type, with polychaetes most likely to be dislodged from depositional sediments, and dislodged worms suffered few mortalities. River measurements in macrohabitats exceeded shear stresses needed to dislodge worms from substrates in some areas. Taken together, it is unlikely that M. speciosa populations will face substantial mortalities as a direct result of flow manipulations. However, definitive statements cannot be made without further study.
Read
