Southern King crabs

Abstract

Lithodid crabs are among the arthropods of the largest size, that further to their occurrence in high concentrations at the shallow waters of the continental shelves confer them a particular economic interest, which has begotten the development of several of the most lucrative fisheries of the world. Added to the gastronomic fame of king crabs, the recent TV show ?Deadliest catch? capture the world-wide public attention on the extreme ocean weather conditions where fishing occurs. Fishery development and management, and more recently the evidence of rapid habitat colonization for some lithodids has stimulated the scientific research on this group (Zaklan 2002; Hall and Thatje 2009). Furthermore, Lithodids are a group of predominately deepsea crustaceans that mostly occupies cold-water habitats. Their optimal levels of growth and survival occur in the temperature range of 5ºC to 10ºC (Hall and Thatje 2011). Lithodids have a wide vertical distribution range, occurring from the intertidal to the deep-sea. The shallow water occurrence is constrained by the temperature, and deep-water lineages of the Lithodinae are excluded from waters exceeding temperatures 13ºC (Hall and Thatje 2009; Hall and Thatje 2011). In South America king crabs are distributed at latitudes between 40-55ºS and northerly on the west margin of South America where the cold waters of the Perú-Chile upwelling zone permit. In coastal waters, or on the continental shelves and shelf breaks of Southern South America, i.e. south of 40ºS, eleven lithodid species occur: Neolithodes diomedeae, Paralomis tuberipes, P. granulosa, P. spinosissima, P. anamerae, Lithodes santolla, L. turkayi, and L. confundens (Table 1; Figure 1). Four species occur off the Islas Malvinas (Falkland Islands; ca. 52ºS 60ºW): P. granulosa, L. confundens, L. santolla and P. birsteini. Off South Georgia Islands (54ºS 38ºW) the target species of an experimental fishery has been P. spinosissima and P. formosa, with by-catch of P. anamerae, P. birsteini, N. diomedeae, and L. murrayi (Purves et al. 2003; Hall and Thatje 2011). In the past half century Lithodes santolla and Paralomis granulosa have sustained profitable fisheries at ?the end of the world?, the touristic denomination of the Southern tip of South America. Here, Chile has a greater extension of coastal waters where king crabs occur and yielded 90% of the historic landings of the region of about 3.000 t per year for both species. Both species are frequently captured together by the same- or adjacent traps and hence they constitute a mixed fishery. In both Chile and Argentina, the fishery begun during 1930s with tangle nets as the fishing gear, and only after 1975 Argentina established some regulation rules. At the start of the fishery P. granulosa was considered as bycatch of L. santolla and therefore discarded due to its lower price. The decreasing yields of L. santolla during the 1980s promoted the fishing for- and marketing of P. granulosa. Landings of both lithodid crabs have always been approximately one order of magnitude higher in the Chilean than in the Argentinean fishery. The fishing activities that developed in the Magellan Straits and neighboring channels were based in Punta Arenas and Puerto Natales whereas the fishery in the Beagle Channel and surroundings has operated from Ushuaia and Puerto Williams. In the Southwestern Atlantic south to 40ºS other lithodid fisheries developed at different degrees, and during the recent year a fishery for Lithodes santolla based in Comodoro Rivadavia has expanded rapidly from the incorporation of larger fishing vessels known as crabbers.