The Prince Edward Islands (PEIs) in the sub-Antarctic Indian Ocean bioregion provide crucial breeding habitat for large populations of seabirds and marine mammals and were declared a Marine Protected Area in 2013. The distribution of plankton in this region is one of the essential components being investigated to support ecoregionalisation of the sub-Antarctic region, a prerequisite for identifying priority areas for conservation. In total, 37 series of Continuous Plankton Recorder (CPR) tows exceeding 50,000 nautical miles have been conducted either wholly or partially within the sub-Antarctic Indian Ocean south of Africa since 1999, but most have not yet been analysed. Zooplankton net sampling has been conducted in the vicinity of the PEIs for over four decades, although mainly during autumn. Annual monitoring of zooplankton in combination with hydrographic parameters along standard transects was initiated in 2013, with one transect extending north to south upstream of the islands, and the other extending from west to east through the archipelago. ZooScan analysis of these samples was initiated in 2022, with taxonomic validation conducted on EcoTaxa, yielding information on biomass (biovolume), abundance, taxonomic composition and size composition. Preliminary results from samples collected in 2018 and 2019 are reported on here, while analysis of samples collected annually from 2013 to 2017 is at an advanced stage. Mean mesozooplankton biovolume in 2018 (~200 mm3.m-3) was twice that in 2019, although abundance was similar (~540-570 ind.m-3). Copepods (similar proportions of calanoids and oithonids) dominated numerically, but chaetognaths comprised a greater proportion of the biovolume (~40%), followed by euphausiids and copepods. Normalised Biomass Size Spectrum (NBSS) analysis revealed flatter slopes in 2018 due to a higher proportion of larger organisms, including euphausiids, amphipods and the copepod Rhincalanus gigas. Future work will include improving taxonomic resolution in EcoTaxa, investigating relationships between species/taxa distributions and hydrographic parameters such as fronts, analysis of recent CPR data, and ultimately building a regional zooplankton atlas.