One unassuming but costly invader that has hitchhiked into San Francisco Bay is the European green crab (Carcinus maenas). African Journal of Marine Science 29, 123–126. Compared with warmer water populations in southern Britain and Holland, the Maine coast population of C. maenas has later settlement of megalopae, slower growth, delayed maturity, longer generation time, and a longer life span. Green crabs can also move to eat eelgrass deeper in the water, which is an important habitat for many juvenile fish, and they feed on young oysters, clams, mussels, and other shellfish commonly found in eelgrass. Masters Thesis. Such differences may account for the inability of populations to establish themselves in waters much colder than those of the central coast of Maine. There are no reports of C. maenas’ family life but as an invasive predator it is reported to feed on various shellfish and also outcompetes native crabs for food resources (Griffiths et al., 2009; Grosholz, E., Ruiz, 2002; Hampton & Griffiths, 2007). Females molt once a year and are very vulnerable until a new shell hardens What’s an invasive species you ask? There is a study in Hout Bay, Cape Town, South Africa that is looking at the manual removal of C. maenas using baited traps and also the efficacy of diver removal. Physical: 2 Cussonia Ave, Brummeria, Pretoria. Auckland. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. In South Africa the voracious predator, C. maenas, thrives in wave-protected areas and as a result dense populations are found in Table and Hout bay harbours, where they out-compete native species (Hampton & Griffiths, 2007). The European Green Crab lives for about four to seven years. Three new conservation projects geared -, GreenBiz — Considered one of the world’s worst invasive species, these crabs feed voraciously on native invertebrates such as young oysters, clams, and even other shore crabs, which can have both ecological and economic consequences. They prefer soft bottoms for living. Journal of Crustacean Biology, 2:31-39. It is easy to tell the difference between female and male crabs. The team adjusted their strategy to leave some adult green crabs present, and helped reduce the population by about 86%. This embrace lasts until the female moults, which can take as long as one week. August 2015. If you see a crab with “five points” on each side of the face, it’s likely a green crab. Crothers, J.., 1967. Some may mistake the green crab for other Pacific Northwest crabs, such as the helmet crab (Telmessus cheiragonus), because the crab is not always green in color, and ranges from brown to dark green. World fish consumption has almost doubled between the 1960s and now, -, Inside Science — No particular sounds or calls have been reported for C. maenas. Robinson, T., Griffiths, C., McQuaid, C., Rius, M., 2005. Once the eggs hatch the first larvae stage form of the life cycle is called the nauplius and is planktonic. d. Griffiths, C.L., Hockey, P.A.R., Schurink, C.V.E., Le Roux, P.J., 1992. 2007). It is reported also as a commercially fished crab (Klassen & Locke, 2007). Class: Malacostraca The bugweed lace bug is […]. European Green Crab. And after the molting the female crab turns over and they mate. The male then picks up the female and carries her with her abdomen facing up; this is referred to as the copulatory embrace. One distinctive characteristic is the five spines located on the sides of each eye. Survival Commission. The South African National Biodiversity Institute (SANBI) contributes to South Africa’s sustainable development by facilitating access to biodiversity data, generating information and knowledge, building capacity, providing policy advice, showcasing and conserving biodiversity in its national botanical and zoological gardens. Chemical communication in mating shore crabs Carcinus maenas. The Asian shore crab also affects this species by consuming settling post-larvae and displacing juveniles from their refuge habitat under rocks (Griffen, Guy & Buck, 2008). European Green crab are used for food and popular in some countries. African Journal of Marine Science 27, 297–306. The European Green crabs can live in all types of protected and semi-protected marine and estuarine habitats (including habitats with mud, sand or rock substrates, emergent marsh and submerged aquatic vegetation. The National Oceanic and Atmospheric Association defines an invasive species as “an organism that causes ecological or economic harm in a new environment where it is not native”. The first evidence of European green crabs in America was found in the 1800s, when crabs were brought over to Cape Cod on a sailing ship. (Ed. Biology: Considering a single female green crab can produce 185,000 eggs in a single year, populations can expand rapidly and early detection is key. The European Green Crab lives for about four to seven years. Reproduction. So how did green crabs spread across the world? The Status and Distribution of Marine Alien Species in South Africa, in: Rilov G, C.J. Canadian Manuscript Report of Fisheries and Aquatic Sciences 2818, 1–82. Females can spawn up to 185,000 eggs at a time (Cohen & Carlton, 1995; Squires, 1990). Although the crab’s common name would lead one to believe they are always green in color, in fact, their coloration varies. Along the central coast of Maine most female Carcinus maenas extruded their eggs in spring. 2005). The European green crab originates from the Atlantic coast of Europe and northern Africa, and tends to live in protected rocky shores, cobble beaches, sand flats, and tidal marshes.