This data package consists of two files to accompany the manuscript Smith J., Flukes E., Keane J.P. (2024) The risky nightlife of undersized sea urchins. Marine and Freshwater Research IN PRESS. Dataset A: 211 Centrostephanus rodgersii (longspined sea urchin) were measured for test diameter and spine canopy at Fortescue Bay, Tasmania, Australia in May-June 2023 (FB_TD_SC.csv) Dataset B: Urchin movement data from Flukes et al. 2023 and associated urchin sizes measured in this study (whole_measured_df.csv)

The spatial extent of C. rodgersii "barrens" was estimated by surveying rocky reef habitat with a towed underwater video system. Sampling took place at 13 regions along the east coast of Tasmania, each comprising 3 subsites, this dataset refers to the Wineglass Bay region, and its 3 subsites: Boot, Nuggets and Wineglass.

The spatial extent of C. rodgersii "barrens" was estimated by surveying rocky reef habitat with a towed underwater video system. Sampling took place at 13 regions along the east coast of Tasmania, each comprising 3 subsites, this dataset refers to the Schouten Island, and its 3 subsites: Baudin, Sarah and Sonerat.

The spatial extent of C. rodgersii "barrens" was estimated by surveying rocky reef habitat with a towed underwater video system. Sampling took place at 13 regions along the east coast of Tasmania, each comprising 3 subsites, this dataset refers to the Fortescue Bay region, and its 3 subsites: Lanterns, Munroe Bight and Thumbs.

Data on captive feeding trials for prey preference in southern rock lobsters on longspined sea urchins, black lipped abalone, shortspined sea urchins and periwinkle.

The spatial extent of C. rodgersii "barrens" was estimated by surveying rocky reef habitat with a towed underwater video system. Sampling took place at 13 regions along the east coast of Tasmania, each comprising 3 subsites, this dataset refers to the North Bruny Island region, and its 3 subsites: Patrick's Bight, Trumpeter Point and Yellow Bluff.

The spatial extent of C. rodgersii "barrens" was estimated by surveying rocky reef habitat with a towed underwater video system. Sampling took place at 13 regions along the east coast of Tasmania, each comprising 3 subsites, this dataset refers to the St Helens region, and its 3 subsites: Binalong Bay, St Helens Island and St Helens Point

The spatial extent of C. rodgersii "barrens" was estimated by surveying rocky reef habitat with a towed underwater video system. Sampling took place at 13 regions along the east coast of Tasmania, each comprising 3 subsites, this dataset refers to the Recherche region, and its 3 subsites: Eliza Point, Fisher Point and Actaeons.

The spatial extent of the long spined sea urchin, Centrostephanus rodgersii, was estimated by divers using underwater visual census methods to survey rocky reef habitats at 13 regions along Tasmania's east coast (between Eddystone Point and Recherche Bay). Within each region 3 subsites were surveyed, and within each subsite 4 belt transects were surveyed. Divers recorded depth, percent substrata type, percent C. rodgersii barrens habitat; abundance of urchins (C. rodgersii and H. erythrogramma), rock lobster (J. edwardsii) and abalone (H. rubra). Divers also recorded algal cover (estimated), C. rodgersii barrens and substratum type using set categories (see below).