Interannual and seasonal trends in abundance, sex ratios, and size of the invasive European green crab, <i>Carcinus maenas</i> (Linnaeus, 1758) (Brachyura: Portunoidea: Carcinidae), in the Great Marsh, Massachusetts, USA

Abstract The European green crab (Carcinus maenas (Linnaeus, 1758)) is one of most invasive species in coastal ecosystems worldwide. Its ability to adapt to various environmental conditions and its omnivorous diet have contributed to its widespread success in marine environments. We investigated from 2014 to 2018 seasonal changes in the abundance, sex ratios, and carapace sizes of C. maenas at 24 sites in Plum Island Sound and Essex Bay, Massachusetts, USA. Overall abundance, measured as catch per unit effort, varied significantly between years (P &amp;lt; 0.001), with the lowest abundance in 2015. Spring abundance was linked to mean winter temperatures from the preceding year, with colder winters associated with lower spring abundance. Sex ratios also varied seasonally across some years, with females predominating in many seasons. Carapace size differed significantly among years (P &amp;lt; 0.001), although no consistent temporal trend was observed. This baseline data can be used to inform future management strategies and trapping efforts.