Abstract
This dataset contains abundance data for Gnathiid isopods, as well as collection metadata. These data were collected as part of a long-term monitoring study of fish-parasitic gnathiid isopods on shallow patch reefs at Lizard Island, Great Barrier Reef, Australia. The data cover the period from 2000 to 2018. Gnathiid isopods, which spend most of their life free-living, were collected using 1-meter square by 1-meter high pyramid-shaped emergence traps placed randomly on the substrate. The total soak time for the traps was approximately 24 hours, divided into day vs night periods. Some of the patch reefs had cleaner fish, which are known predators of gnathiid isopods, removed over the course of the study (removal) while for others, cleaner fish remained (control).