EXPLORATORY DEEP-SEA FISHING IN THE FALKLAND ISLANDS, SOUTH-WESTERN ATLANTIC

Records of demersal deep-sea fish assemblages in waters around the Fal kland Islands (Patagonian shelf area) are rare. Twenty deep-water stat ions to the east and south of the Falkland Islands were sampled by com mercial bottom trawl deployed in upper, middle and lower benthopelagic zones (depth range of approximately 500-1000 m). Forty-one species (2 2 families) of teleost fish were recorded, 10 species (two families) o f elasmobranch and one species of agnathan. Different assemblages of f ish were found to characterize each depth zone (e.g. Moridae in deeper waters, Bothidae and Rajidae in shallower waters), with diversity bei ng greatest in the mid-zone and biomass greatest in the upper and lowe r zones. Some species occurred in ail zones but showed depth-related a bundance. Four species, namely the grenadiers Macrourus carinatus and Coelorhynchus fasciatus, the southern blue whiting Micromesistius aust ralis, and the Patagonian toothfish Dissostichus eleginoides, accounte d for 85% by weight of all fish caught. Quantitative sampling of selec ted species revealed depth-related variations in their population stru cture. Length-frequency analyses are presented for M. carinatus and D. eleginoides and show a tendency for larger individuals to inhabit dee per water. Discard rates from the commercial catch were sometimes high , particularly for the smaller species, raising concerns about the imp act of a fishery on by-catch species. The potential for deep-sea fishe ries in Falkland waters is discussed and Further studies are suggested in the light of developing oil, gas and fishing industries. The prese nce of some invertebrate taxa is recorded. (C) 1996 The Fisheries Soci ety of the British Isles