SummaryA brief summary is given of the chemical and biological oceanography of Bass Strait, as far as it is relevant to the food supply of Little PenguinsEudyptula minorand the environment in which they live. Four water masses are considered to affect Bass Strait. These are North Bass Strait Water, Central Tasman Water, Subantarctic Water and East Australian Current Water. They vary greatly in nutrient status and the effects of this on productivity (about which little is known) and resulting plankton biomass is discussed. It appears that phytoplankton biomass is greatest near the extremities of Bass Strait but zooplankton biomass may be greater within Bass Strait.