Natural fluctuations in the abundance of krill with due regard to global climate changes in the southern hemisphere: forecasting possibilities

The eco systematic studies in biology and hydrology conducted in the Atlantic sector of the South Ocean in recent years made it possible for scientists to establish a rather clear relationship among the winter and spring ice cover variations, summer water surface temperature, and "success" in the reproduction of krill (Euphausia superba) and salp (Salpa tompsoni) (SC-CAMLR-XVI4; SC-CAMLR-XVV3).
The analysis of multiannual observations ( 1977-1997) conducted by Siegel (Siegel et al., 1997) and other researches in the Antarctic Peninsula Subarea 48.1 showed good correlation between the strong year-classes of krill and severe winters when the ice-cover extended itself northwards considerably as opposed to the multiannual average level, and late thawing of ice. On the contrary, poor generations of krill were formed during the years when the winter position of the ice edge was south of the average multiannual level. The abundance of salp went up sharply in the areas of krill distribution in summer during such years of moderate winter in higher surface temperature. Salp occurred in mass constantly both in scientific and commercial fishing gear. Poor year-classes of krill and upsurges in the abundance of salp were recorded in seasons 1982-1983 and 1988-1989 (Siegel and Loeb, 1995) i.e. during the years of development of El Niño off South America (Jordan, 1991). These facts may lead one to assume that the last El Niño can also cause warming in Subarea 48.1 affecting reproductive capacity in krill.