Coarse-scale relationships between seabirds and zooplankton off south-eastern Tasmania

Abstract

Observations were made of seabird and zooplankton distribution in the waters adjacent to south-easternTasmania to examine correspondence at coarse scales (tens of kilometres). The distribution of seabirds was related mainly to changes in the water depth (and distance from land) over the length of the transect, whereas the distribution of zooplankton related to temporal changes. Significantly different associations of seabird species occurred in Storm Bay (mainly species breeding within the bay), and over the shelf-edge (with many non-breeding species dominant). Zooplankton diversity varied during the study, being greatest at the beginning (May) and end (September) of the study. Little correspondence was found between the distribution of seabirds and zooplankton at the community level, but there were significant relationships for several species, such as diving petrels and gannets. The lack of an overall correspondence between seabirds and zooplankton may have been due to the patchiness of seabird and zooplankton distribution, limits to the requirements of seabirds to find maximum prey densities (instead only needing to find ‘enough’), the lack of certainty about whether seabirds were foraging when observed, and behavioural interactions among seabirds.