An assessment of the impact of krill fishery on penguins in the South Shetlands

The competition between Japanese krill fishery and penguins during their breeding season (December-March) in the South Shetland Islands (Subarea 48.1) was assessed based on available information on fishery, penguins and krill biomass. The catch is very low in December followed by roughly equivalent amount (3,000-10,000 t/10-day) for the following three months, with its increased fishing intensity to the shelf and slope of Livingston or Elephant Island. In contrast, the food consumption by penguins is estimated to be large in the shelf and slope near King George Island (11,680 t/10-day), whereas small near Livingston (2,570 t/10-day) and Elephant (220 t/10-day) Islands. This little overlap between the main fishing and foraging areas implies less competitive relationship between fishery and penguins. Estimated krill biomass varies considerably within the favorite fishing areas due to the movement of krill into and out of the area, but high krill biomass (100-1000 x103t) usually existed there. Compared with the amount of biomass (100-1000 x10 3t) and the degree of its variability (the order of 100 x10 3t/10-20 day), the present catch rate (≤10 x103t/10-day) is smaller by one or more orders of magnitude within the localized areas. Hence, from the view point of the quantity of catches as well, present fishery is very unlikely to have an adverse impact on the local krill biomass and hence on penguins.