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Taxonomische classification
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(H. Milne Edwards, 1837)

Large spines of carapace broad and flattened, about as wide as long, much larger than the small spines. First abdominal somite without any squamiform sculpturation. Following somites with only a single transverse row of large squamae before transverse groove of somite, sometimes with some very small squamae just before or behind it. Posterior half of abdominal somites behind transverse groove without squamiform structures.

Type locality: "Habite le Chili", now restricted to Juan Fernandez Archipelago, Chile. Type material in MP, no longer extant (not found in 1989).

Geographical Distribution:
The range of the species is restricted to: (1) the waters around the Juan Fernandez Archipelago, 33°35'-33°49'S 78°45'-80°49'W: Isla Robinson Crusoe ( = Isla Más a Tierra), Isla Marinero Selkirk ( = Isla Alejandro Selkirk, = Isla Má Afuera) and Isla Santa Clara, and (2) the waters around the Islas Desventuradas, 26°17'-26°22'S 79°50'-80°6'W: Isla San Felix and Isla San Ambrosio.

Habitat and Biology:
A species inhabiting a rocky and partly sandy environment at depths of 2 to 200 m. Water temperature between 13° and 19°C. Eggs spawned between August and November and carried for about 11 months. Although there is some migration to deeper waters from the end of September onwards, the species never disappears completely from the coast. In January, the migration back to shallow waters starts. The food consists of algae, smaller and larger molluscs and crustaceans, and dead animal matter of any kind. The species is predated by various fishes.

Maximum body length 48 cm (males) and 46 cm (females), carapace length 22 cm (males) and 19 cm (females). Reports of total body lengths of 60-70 cm have to be considered with much reserve.

Interest to Fisheries:
The early navigators who visited Juan Fernandez like Jacob Roggeveen in 1722 and George Anson in 1741 already mentioned that the lobsters were found there "in such abundance near the water's edge (of Isla Robinson Crusoe) that the boat-hooks often struck into them, in putting the boats to and from the shore" (Walter,1776: 125, 126), also their excellent a" quality as food was commented upon. Molina (1808: 144; English translation of Molina's original (1782) Italian edition) mentioned that "Lobsters are also found in such quantities that the fishermen have no other trouble to take them, than to strew a little meat upon the shore, and when they come to devour this bait, as they do in immense numbers, to turn them on their backs with a stick. By this simple method many thousands are taken annually, and the tails which are in high estimation, dried and sent to Chili" Albert (1898: 6) mentioned that the species was usually fished at depths between 7 and 14 m. Skottsberg (1956: 178), almost 50 years later, stated that "nowadays the best catch is made in depths from 40 to 80 meters". Evidently, the intensity of fishing drove the species to deeper water, and the easy method of picking them by hand was replaced by lobster pots.
By the end of the 19th century, canning lobster tails was tried without too much success; canned and live lobsters were then exported to Chile. In 1970, the main gear for catching the lobsters were lobster pots and they perhaps still are. Evidently, most lobsters are exported live to the mainland. According to FAO statistics, the annual catch of the species was 36 tons in 1987 and 29tons in 1988. The fishery is of the greatest importance in the Archipelago and gives employment to a large part of the population. Experimental work on reproduction and development in captivity of this species is being conducted in Chile.
Protective measures are in force and well adhered to: (1) the minimum legal size is a carapace length of 11.5 cm, (2) ovigerous females have to be put back into the sea, (3) the season is closed from 15 May to 30 September.

Juan Fernandez rock lobster (Jasus frontalis)