Abalones at risk: A global Red List assessment of Haliotis in a changing climate

surpassed wild abalone fisheries accounting for more than 98% of the total abalone market [54], including regions such as Chile which lack naturally occurring wild abalones. In very few regions wild fisheries still dominate, with wild-taken abalones being the preferred option in some countries, especially for ceremonial occasions. Abalones reflect many of the conservation issues confronting shallow-water marine taxa: 1) fished in large numbers for human consumption with the threat of overexploitation by both legal and illegal means; 2) necessity for closely packed assemblages to ensure fertilisation suc- cess that becomes vulnerable through overfishing; 3) exposure to the increasing prevalence of MHWs resulting from a changing climate directly impacting their mortality and/or resulting in loss of algal food resource; 4) reduction in habitat through invasive species in particular sea urchins that compete for food; and 5) vulnerability to surface-borne pollutants, including run- off from industry and agriculture, pathogen escapes from aquaculture facilities, and anti-foul- ing agents used on hulls of vessels. By using the standard assessment methodology developed by the IUCN Red List, the objective of our research was to identify those species whose conser- vation status may be affected by these and other threats. The detailed results summarised here are published and freely available on www.iucnredlist.org. Methods The IUCN Red List is the world’s leading resource for describing the global conservation status

of animals, plants and fungi, and uses a standard methodology to classify species into one of nine categories supported by a codified set of criteria. The assessment process examines the impact of threats on species, but also includes the effect of any recovery programmes. For each species, data are collected using a standard format together with images, maps and supporting documentation [55]. Before developing the database for our global abalone assessment, we referenced the World Register of Marine Species (www.marinespecies.org) to create a taxonomic list of all 54 species of Haliotis which we loaded into the Species Information System (SIS), the online assessment tool of the IUCN Red List of Threatened Species that acts both as a repository for the data and as a ‘calculator’, described below, to determine the categories and criteria that are central to establishing the level of threat. Categories and criteria Each species assessed under the procedures of the IUCN Red List is assigned a category (Table 1) that assigns the level of risk, provided sufficient data are available to make such deter- mination [55]. There are nine categories, of which the three most at risk (Critically Endan- gered, Endangered and Vulnerable) are collectively named as threatened categories. The assessment process is common to all species, whether animals, plants or fungi, and the cate- gory is assigned on the basis of five criteria (A-E) (Table 2) established from research. The cri- teria code(s) appropriate to a taxon are determined from those elements that influence its

status, e.g. population decline, changes in area of distribution, etc. selected from a series of tables and sub-tables. For example: Criterion A has four divisions: A1: population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased. Criterion A2 is as per A1 but when the causes may not be reversible or understood or ceased. Criterion A3 refers to future projections while A4 refers to both the past and future. These population reductions require to be further supported by one or more elements from a sub-table, i.e. (a) from direct observation; (b) an index of abundance appropriate to the taxon; (c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality; (d) actual or potential levels of exploitation; and/ PLOS ONE Abalones at risk: A global Red List assessment of Haliotis PLOS ONE | https://doi.org/10.1371/journal.pone.0309384 December 23, 2024 5 / 25