Analysis of haul data from the South Georgia krill fishery
Data from individual hauls carried out by vessels operating in the South Georgia krill fishery between 1994 and 1996 were examined and a range of descriptive measurements reflecting the fishery operation were produced. The measurements emphasise that the krill fishery at South Georgia was geographically focused, operating in a limited area along the shelf edge on the northern coast of the island. Each day several hauls were undertaken by each vessel (average 7.9 in 1993,9.9 in 1995, and 7.0 in 1996), with hauls producing higher catch rates during the middle of the day. Individual hauls were examined to establish the time required for each phase of the fishing operation. The times associated with shooting and hauling the net were usually short and showed little variation, whereas the time associated with the actual fishing period was longer and more variable. The time between consecutive hauls was almost as long as the fishing period and showed similar levels of variability. Distances moved between consecutive hauls were generally small, suggesting that little effort was spent searching for fishable swarms beyond the near neighbourhood. The range of measurements describing the fishery indicates that differences existed between years, with 1995 being a better season than either 1994 or 1996. Aspects of mesoscale variability are discussed in relation to previous attempts to model fisheries data and to derive suitable abundance indices that are sensitive to changes in biomass. The focused nature of the fishery at South Georgia suggests that fisheries-based indices may be of value for management purposes, consequently further detailed analysis would be useful.