Technical Report
 

Status of the European Green Crab, Carcinus maenas, (aka 5-spine crab) in Oregon Estuaries. Report for 2022

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https://ir.library.oregonstate.edu/concern/technical_reports/73666d40c

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  • The European green crab (Carcinus maenas) has persisted in Oregon and Washington coastal estuaries since the late 1990s. A strong year class arrived during the 1998 El Niño, but numbers decreased and remained below 1 per trap per day until the arrival of the 2015-2016 El Niño. Since then, numbers have increased to an average of around 4-6 crabs per trap per day for intertidal sites and ~ 9 per trap per day in the shallow subtidal. Measurable ecological impact is predicted to occur at around 10-20 per trap per day (Grosholz et al. 2011). Between the two major El Niños, recruitment of young green crabs has been sporadic, with many years of recruitment failures. But after the 2015-2016 El Niño recruitment has been good every year. The Davidson Current transporting larvae from California during the winter no longer appears to be the only source of larvae for our coastal estuaries (Behrens Yamada, Fisher and Kosro 2021). Now that the populations in Oregon, Washington and British Columbia have built up, we have evidence for local larval production and seeding from a genetically distinct population on Vancouver Island (Alan Shanks and Carolyn Tepolt, pers. com.). This report is a compilation of trapping data for Carcinus maenas from various sources and estuaries. These include the following: 1) Catches of adult crabs in Yaquina Bay using Fukui traps set in the intertidal and in the shallow subtidal. The latter were set at 22 sites along a salinity gradient from South Beach Marina to the Port of Toledo by Mitch Vance of Oregon Department of Fish and Wildlife. 2) Catches of adult crabs at 3 sites in the Salmon estuary using Fukui traps set in intertidal areas by volunteers and by Rebecca Flitcroft from the United Stated Department of Agriculture. 3) Summary of catches of crabs trapped in Coos Bay by Shon Schooler, interns and technicians of South Slough National Estuarine Research Reserve. For detailed data on various sites in Coos Bay see Schooler et al. (2022). 4) Catches of adult crabs in Siuslaw and Umpqua estuaries by Shon Schooler and interns. 5) Average catches of Young-Of-The-Year (YOTY, or Age-0) crabs at the end of their first growing season, from 4 Oregon estuaries and Willapa Bay, Washington. This 25-year data set allows us to compare catches of YOTY crabs between years and between estuaries (Figure 3).
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