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Distribución y estructura poblacional del cangrejoHalicarcinus planatus (Brachyura, Hymenosomatidae) en el Canal Beagle, Tierra del Fuego America and has a sub-Antarctic distribution, including the peri-Antarctic islands and New Zealand. In this paper, we report the abundance and population structure of H. planatus for a year in the intertidal zone of Bahía Brown, Beagle Channel, Tierra del Fuego. Moreover, we show variations in the population structure in other beaches and environments of the channel. In contrast with males, female density showed monthly variations and was higher during austral summer months. High densities of H. planatus could be related with low mortality during the larval stage and oceanographic features of Bahía Brown, probably enhanced by the presence of both culture and mussel beds, substrates where settlement would occur. The populational sex ratio was biased towards females only in summer, while the operational sex ratio was biased towards males during all periods studied, suggesting strong competition among males for mating. In turn, males were present only in the intertidal zone of Bahía Brown and Macrocystis pyrifera but were absent in the other studied intertidal areas.This is perhaps related to the lack of shelter in the subtidal zone of Bahía Brown. Recruitment occurs in two different periods, summer (JanuaryFebruary) and autumn-winter (May-June), which corresponds with the two larval cohorts of H. planatus in the Beagle Channel.Key words: Abundance, sex ratio, sexual maturity, recruitment, sub-AntarcticResumen.-El cangrejo Halicarcinus planatus es el único himenosomátido que habita el extremo austral de Sudamérica, con una distribución subantártica, incluyendo las islas periantárticas y Nueva Zelanda. En este trabajo, se presenta información sobre la abundancia y estructura poblacional de H. planatus en el intermareal de Bahía Brown, Canal Beagle, Tierra del Fuego durante un año. Además, se muestran las variaciones en la estructura poblacional en otras playas y ambientes del canal. A diferencia de los machos, la densidad de hembras mostró fluctuaciones mensuales en el intermareal de Bahía Brown y fue mayor durante los meses de verano. Las altas densidades de H. planatus podrían relacionarse con la baja mortalidad de estadios larvales y las características oceanográficas de la bahía, probablemente aumentado por la presencia de bancos y cuerdas de cultivo de mejillones, sustratos donde ocurriría el asentamiento de H. planatus. La proporción de sexos poblacional estuvo sesgada hacia las hembras solo en verano, mientras que la proporción sexual operativa se sesgó hacia los machos durante casi todo el período estudiado, sugiriendo una fuerte competencia entre machos por el apareamiento. A su vez, los machos solo estuvieron presentes en el intermareal de Bahía Brown y en los grampones de Macrocystis pyrifera pero no se encontraron en el resto de los intermareales estudiados, probablemente relacionado con la ausencia de refugio en el submareal de Bahía Brown. El reclutamiento existiría ...

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