The timing of Carcinus maenas recruitment to a south-east Australian estuary differs to that of native crabs

Strong seasonal trends in reproduction and early development of many invasive species are commonplace and may differ between introduced and native ranges, reflecting differences in abiotic conditions that trigger reproduction, or in selective pressures. The invasive crab Carcinus maenas has been present in south-east Australia for over 100 years, but little is known about its recruitment to benthic substrates in this introduced range. This study assessed the timing of C. maenas and native crab recruitment to Merimbula Lake (36.89^oS, 149.92^oE) south-eastern Australia between August 2011 and October 2013. It also assessed the effectiveness of four different types of recruitment bags for detecting the invasive crab. Carcinus maenas recruited in greater numbers to bags that contained live oysters than those with oyster shell, artificial turf or without structure. Recruitment of C. maenas peaked in the late winter and spring, while recruitment of most native species peaked in autumn. The timing of C. maenas recruitment contrasted its native European range where recruitment typically occurs in summer and autumn. Although likely triggered by the warmer water temperatures of south-eastern Australia, this differing reproductive phenology of C. maenas between its native and Australian range may also modify its interactions with native crab recruits.