A declining trend in the abundance of Notothenia rossii marmorata and Notothenia gibberifrons observed in fjords in two sites in the South Shetland Islands
A declining trend observed in the abundance of Notothenia rossii marmorata and Notothenia gibberifrons in fjords in two sites in the South Shetland Islands (Subarea 48.1), is analyzed by a nested ANOVA and demonstrated as significant. The material for the current study was obtained with trammel nets at Potter Cove, King George/25 de Mayo I., over a period of eight years from 1983 to 1990 and in waters around Half-Moon I., Moon Bay, in 1989. The analysis was based on the proportion of catches of the abovementioned species in relation to Notothenia neglecta, a species with similar ecological habits in the fjords. Since sampling by this method did not utilize a consistent amount of effort between years, the analysis made use of standardized catch data by expressing the catches of N. rossii and N. gibberifrons in proportion to the catches of N. neglecta. A similar declining trend had been reported in the 1960s and 1970s for neighbouring sites in the South Shetland Islands. This phenomenon might be explained as a consequence of the depletion of the stocks due to commercial exploitation in the area in the early 1980s.