Occurrence of Lithodes Confundens (Decapoda: Anomura) in the Intertidal of the Southwestern Atlantic

Abstract We provide the first biological data for the southern king crab Lithodes confundens, found intertidally on the Atlantic coast of southern South America (51°21′S-54°20′S). Between October and December 1997 and in December 1999, specimens were found during the ebbtide in crevices of the wave abrasion platform. The size of animals progressively increased from ∼ 50 mm carapace length (CL) in October to ∼ 105 and 75 mm CL in December for males and females, respectively. The sex ratio increased from October to December, from 1:1 to 2:1 male : female. Females molted during December. A total of 61 mating pairs were found at Bahía Grande (51°21′S, 69°02′W), between 16 November and 28 December 1997, and represented 31% of a total of 399 captures. Mating pairs were in precopulatory embrace, which was formed by a male in intermolt condition and a female in ecdysis. The male was always larger than the female. The relative growth of the male right chela was studied with the MATURE computer routine for two different chela dimensions, length and width. Slopes of relationships between chela sizes and CL changed at 89.8 and 87.3 mm CL, respectively. The estimated size of physiological maturity for 82 females was 68.3 mm CL. The smallest male participating in mating pairs was 75.2 mm CL. We suggest 100 mm CL as the legal size for fishery management purposes.