Estimated Entrainment of Dungeness Crab During Dredging For The Columbia River Channel Improvement Project

Pearson, Walter H. ; Williams, Greg D. ; Skalski, John R.

Pacific Northwest National Laboratory (U.S.)

关键词: Crabs;    Adults;    Dungeness Crab;    Salinity;    Entrainment;   

DOI  :  10.2172/949177
RP-ID  :  PNNL-14129
RP-ID  :  AC05-76RL01830
RP-ID  :  949177

美国|英语

来源: UNT Digital Library

【 摘 要 】

The studies reported here focus on issues regarding the entrainment of Dungeness crab related to the proposed Columbia River Channel Improvement Project and provided direct measurements of crab entrainment rates at three locations (Desdomona Shoals, Upper Sands, and Miller Sands) from RM4 to RM24 during summer 2002. Entrainment rates for all age classes of crabs ranged from zero at Miller Sands to 0.224 crabs per cy at Desdemona Shoals in June 2002. The overall entrainment rate at Desdomona Shoals in September was 0.120 crabs per cy. A modified Dredge Impact Model (DIM) used the summer 2002 entrainment rates to project crab entrainment and adult equivalent loss and loss to the fishery for the Channel Improvement Project. To improve the projections, entrainment data from Flavel Bar is needed. The literature, analyses of salinity intrusion scenarios, and the summer 2002 site-specific data on entrainment and salinity all indicate that bottom salinity influences crab distribution and entrainment, especially at lower salinities. It is now clear from field measurements of entrainment rates and salinity during a period of low river flow (90-150 Kcfs) and high salinity intrusion that entrainment rates are zero where bottom salinity is less than 16 o/oo most of the time. Further, entrainment rates of 2+ and older crab fall with decreasing salinity in a clear and consistent manner. More elaboration of the crab distribution- salinity model, especially concerning salinity and the movements of 1+ crab, is needed.