European Green Crab

Carcinus maenas has a carapace up to 60 mm (2.4 in) long and 90 mm (3.5 in) wide, but can be larger outside its native range, reaching 100 mm (3.9 in) wide in British Columbia. The carapace has five short teeth along the rim behind each eye, and three undulations between the eyes. The undulations, which protrude beyond the eyes, are the simplest means of distinguishing C. maenas from the closely related C. aestuarii, which can also be an invasive species. In C. aestuarii, the carapace lacks any bumps and extends forward beyond the eyes. Another characteristic for distinguishing the two species is the form of the first and second pleopods (collectively the gonopods), which are straight and parallel in C. aestuarii, but curve outwards in C. maenas. The colour of C. maenas varies greatly, from green to brown, grey, or red. This variation has a genetic component, but is largely due to local environmental factors. In particular, individuals which delay moulting become red-coloured rather than green. Red individuals are stronger and more aggressive, but are less tolerant of environmental stresses, such as low salinity or hypoxia. Juvenile crabs on average display greater patterning than adults.

Carcinus maenas is native to European and North African coasts as far as the Baltic Sea in the east, and Iceland and Central Norway in the north, and is one of the most common crabs throughout much of its range. In the Mediterranean Sea, it is replaced by the closely related Mediterranean green crab species C. aestuarii. Carcinus maenas was first observed on the east coast of North America in Massachusetts in 1817, and may now be found from South Carolina northwards; by 2007, this species had extended its range northwards to Maine and Placentia Bay, Newfoundland. In 1989, the species was found in San Francisco Bay, California, on the Pacific Coast of the United States. The green crab did not begin to expand its range until 1993, before rapidly expanding northward, reaching Oregon in 1997, Washington in 1998, and British Columbia in 1999, extending its total range by 750 km (470 mi) in 10 years. Invasive green crabs were first discovered in Alaska in 2022 by Metlakatla Indian Community Department of Fish and Wildlife. By 2003, C. maenas had extended to South America with specimens discovered in Patagonia. In Australia, C. maenas was first reported "in the late 1800s" in Port Phillip Bay, Victoria, although the species was probably introduced as early as the 1850s. …

Carcinus maenas can live in all types of protected and semiprotected marine and estuarine habitats, including those with mud, sand, or rock substrates, submerged aquatic vegetation, and emergent marsh, although soft bottoms are preferred. Adult specimens of C. maenas are euryhaline, meaning they can tolerate a wide range in salinity (from 4 to 52 ‰), and survive in temperatures of 0 to 30 °C (32 to 86 °F). The wide salinity range allows C. maenas to survive in the lower salinities found in estuaries, and the wide temperature range allows it to survive in extremely cold climates beneath the ice in winter. Early life stages are more constrained in their tolerances; for example, larvae survive from hatch to metamorphosis to megalopa at temperatures between 12 and 27 °C. A molecular biological study using the COI gene found genetic differentiation between the North Sea and the Bay of Biscay, and even more strongly between the populations in Iceland and the Faroe Islands vs. those elsewhere. This suggests that C. maenas is unable to cross deeper water. Different native populations of C. maenas differ in traits such as larval and adult thermal tolerance, larval salinity tolerance, and body mass at hatching and at metamorphosis. Females can produce more than 400,000 eggs, and larvae develop offshore in several stages before their final moult to juvenile crabs in the intertidal zone. …

In its native range, European green crab is mostly used as an ingredient in soups and sauces. However, the closely related Mediterranean green crab (C. aestuarii) has a thriving culinary market in Italy, where fishermen known as moecante cultivate soft-shell green crabs (moeche in Venetian, moleche in Italian) and sell hard-shell crabs for their roe (masinette). Several groups in New England have successfully adapted these methods to produce soft-shell green crabs from the invasive species. In New England where invasive green crab populations are high, various groups have looked into using green crabs in cuisine. In 2019, The Green Crab Cookbook was released; it included recipes for soft-shell green crab, green crab roe, green crab stock, and green crab meat. One of the book's co-authors went on to found Greencrab.org, an organization dedicated to developing culinary markets for the invasive green crab. In addition to partnering with local chefs and wholesalers for supply chain development and market studies, Greencrab.org has continued to develop green crab recipes and processing techniques. Researchers at the University of Maine have actively been developing value-added green crab products, with the goals of driving business interest, stimulating a commercial green crab fishery, and alleviating predation effects. …

Carcinus maenas was first given a binomial name, Cancer maenas, by Carl Linnaeus in his 1758 10th edition of Systema Naturae. An earlier description was published by Georg Eberhard Rumphius in his 1705 work De Amboinsche Rariteitkamer, calling the species Cancer marinus sulcatus, but this antedates the starting point for zoological nomenclature. A number of later synonyms have also been published:

Monoculus taurus Slabber, 1778 Cancer granarius Herbst, 1783 Cancer viridis Herbst, 1783 Cancer pygmaeus Fabricius, 1787 Cancer rhomboidalis Montagu, 1804 Cancer granulatus Nicholls, 1943 Megalopa montagui Leach, 1817 Portunus menoides Rafinesque-Schmaltz, 1817 Portunus carcinoides Kinahan, 1857 The lectotype chosen for the species came from Marstrand, Sweden, but it is assumed to have been lost. In 1814, writing for The Edinburgh Encyclopaedia, William Elford Leach erected a new genus, Carcinus to hold this species alone (making it the type species of the genus, by monotypy). In 1847, Nardo described a distinct subspecies occurring in the Mediterranean Sea, which is now recognised as a distinct species, C. aestuarii.