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Relationship between ocean ecosystem indicators and year class strength of an invasive European green crab
The annual abundance of the non-native European green crab, Carcinus maenas, in Oregon estuaries varies greatly with ocean conditions. Behrens Yamada et al. (2021) find the year class strength of young crabs is strongly linked to ocean indicators during their planktonic larval development. Among the best indicators for green crab year class strength are winter water temperatures, the sign of the Pacific Decadal Oscillation index, the day of physical and biological spring transitions, and negative biomass anomalies of northern copepods. These correlations suggest that green crabs need (1) warm winters (temperature > 10°C), which enable larvae to complete their development in the nearshore, (2) strong northward flow of coastal waters during winter, which allows larvae to be transported from established populations to the south and (3) coastal circulation patterns that keep larvae close to shore, where they can be carried by wind and tidal currents into estuaries to settle. Behrens Yamada et al., analyzed data over 22 years from 1998-2019.
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A key to their analysis was long-term records maintained over the Oregon shelf by a variety of programs including the Ocean Observatories Initiative (OOI). Over their analysis years, exceptionally strong year class strength was reported in 2018-2019. During these years, most of the ocean conditions described above were moderate, yet green crab recruitment was very high. The factor most strongly related to the high recruitment was stronger than average northward flow as observed at the OOI Endurance Array Oregon shelf mooring (CE02SHSM) (Figure 28).
Behrens Yamada, S, JL Fisher, and PM Kosro (2021) Relationship between ocean ecosystem indicators and year class strength of the invasive European green crab (Carcinus maenas). Prog. Ocean. 196 (2021) 102618. https://doi.org/10.1016/j.pocean.2021.102618.
