A revised assessment of the impact of the krill fishery on penguins in the South Shetlands

This paper is a revision of the assessment of the competition between the Japanese krill (Euphausia superba) fishery and penguins (WG-Krill-93/7). Main fishing areas were confined to the slope and shelf to the north of either Livingston or Elephant Islands. In contrast, main foraging areas of penguins are considered to be formed in areas to the north of King George, Nelson and Robert Islands, and around Low, Clarence and Deception Islands. This little overlap between the main fishing and foraging areas is resulted from that large colonies of the dominant penguin (chinstrap penguins, Pygoscelis antarctica) are closely associated with areas where sea-ice disappears earlier in spring, not necessarily with areas of high krill abundance. The overlap between trawling depth and foraging dive depth of penguins was also insignificant. Furthermore, less similarity between krill caught by trawlers and those captured by penguins was observed. The above mentioned results imply a low level of competition between the fishery and penguins. Krill biomass was estimated to be as large as 200-1500 xl03 tonnes within the preferred fishing areas during the breeding season. Compared with the level of biomass (≥200 xl03 tonnes) and its variability (the order of 100 xl03 tonnes/half-month period), the present catch rate (≤13 xl0 3 tonnes/half-month period) is smaller by one or more orders of magnitude within the localized areas. Thus, the present fishery is very unlikely to have an adverse impact on the local krill biomass and hence on penguins,. when catch levels are also taken into account.