Pearl culture in Fiji relies on a supply of pearl oysters obtained through the strategic deployment of spat collectors. Although the design and deployment of spat collectors aim to maximize the recruitment of pearl oysters (Pinctada and Pteria spp.), this activity incidentally captures many other bivalves as bycatch. This study explored whether tropical rock oysters (specifically Magallana bilineata and Saccostrea spp.) were present and sufficiently abundant as bycatch from pearl oyster spat collectors, to support additional commercial opportunities. The results showed that the absolute (0.7 ± 2.1 spat collector^–1) and proportional (2.9% of all bivalves) abundance of these taxa was very low, which would limit oyster harvest in meaningful quantities. Although the prospect of creating additional revenue streams from bycatch could be seen as an incentive to on-grow and sell tropical rock oysters despite their low abundance, it is argued that greater benefit would come from prioritizing activities related to pearl oysters and associated downstream products such as mabé pearl, shellcraft, and pearl-meat production. Ultimately, existing spat collection activities within the cultured pearl sector did not have the anticipated potential to support supplemental aquaculture of tropical rock oysters.