Shipworm (Bankia setacea) host selection habits at the port of Everett, Washington |
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| Authors: | R I Gara F E Greulich K L Ripley |
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| Institution: | 1. College of Forest Resources, University of Washington, 98195, Seattle, Washington
2. Department of Natural Resources, State of Washington, Box 47037, 98504, Olympia, Washington
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| Abstract: | Studies were performed at the Port of Everett, Washington, and the associated Snohomish River Estuary, to establish settlement patterns of veliger of the shipworm,Bankia setecea. Estuarine waters at the Port of Tacoma also were sampled for shipworm activity. Veliger settlement patterns at the Port of Everett indicated settlement took place all year, with major activity during August–October. This also was a period of reduced Snohomish River flow; therefore, logs stored in the estuary during 1989 at 1.9–3.0 km up river from the river’s mouth were attacked byB. setacea as the salinity of these log-storage sites increased. In contrast, major movement of veligers at the Port of Tacoma was in early summer; high water temperatures were though to prevent midsummer settlement. The upper side of wooden samplers were significantly more infested by shipworms than the under side. Veliger settlement increased evenly with depth down to the mudline discontinuity. Veligers attacked fresh wooden samplers at a significantly higher rate when these samplers were placed next to wood that had been exposed previously to shipworm attack for over 8 wk. There was proportionally less attack on fresh wooden samplers when these samplers were placed next to material exposed to attack for 4 wk; the least attack on fresh wooden samplers occurred when they were placed adjacent to unnattacked wood that had been exposed to marine water for a month (screening prevented this material from being infested). These results suggested that there were waterborne cues emanating from previously-attacked material that attracted veligers. There were significantly moreB. setacea attacks on wooden samplers that were half-covered with Douglas-fir bark as compared with samplers half-covered with foam plastic. These data confirmed observations that shipworms severely attack Douglas-fir logs at sites where the bark has been peeled off, an indication that settling veliger larvae may respond to host-mediated chemical cues. |
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