Moving northwards: Invasive Green Crab ( Carcinus spp.) Expands into the Southwestern Atlantic
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The invasive European green crab ( Carcinus spp.) has become a significant ecological concern due to its rapid global spread and impact on coastal ecosystems. In the Southwestern Atlantic, the northernmost population was recently recorded in the San Matías Gulf, providing an opportunity to study its demographic and life-history traits at the leading edge of its range. We conducted a comprehensive analysis of this population, assessing sex ratio, population density, size distribution, and the size at which 50% of females were ovigerous (SM 50 ). Our findings revealed a pronounced male-biased sex ratio (1.50 males per female) and a relatively low population density (0.52 crabs.m -2 ), suggesting early-stage population establishment. The size range of individuals aligned more closely with Carcinus aestuarii than C. maenas , raising the possibility of hybridization or misidentification. Ovigerous females were present throughout most of the year, highlighting an extended reproductive period and adaptability to local environmental conditions. These traits, combined with rapid range expansion, underscore the invasive potential of Carcinus spp. and its ecological implications for the San Matías Gulf. Long-term monitoring and genetic analyses are essential to clarify species composition and inform management strategies to mitigate further spread and impacts of this invasive population.
Simple Summary
Green crabs are invasive species that threaten coastal ecosystems around the world by competing with native animals and damaging habitats. Recently, a population of green crabs was discovered in the San Matías Gulf in Argentina, marking the furthest north this species has been found in the Southwestern Atlantic. We studied this population to understand its characteristics and how it might grow and spread in the future. We found that male crabs were more abundant and larger than females, and the overall population density was relatively low, which suggests that the population is still becoming established. Interestingly, the size of the crabs in this area is more similar to a related, less common species of green crab, which has also been reported in the Southwestern Atlantic, than to the more widely studied species. Since these two species are nearly identical in appearance, they are often misidentified, making it important to study their genetic makeup. Female crabs carrying eggs were found throughout most of the year, showing that this population can adapt well to local conditions and reproduce for extended periods. These findings suggest that the population could expand further and have serious impacts on native species and ecosystems. Monitoring this population over time will help scientists and policymakers better manage the spread of this invasive crab.
