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

Results Overview Abalones can generally be classified into two groups–those that are (or have been) fished com- mercially and those that are generally not exploited owing to their small size. Although lacking data, some of the small non-commercial species may also be taken incidentally as food, but this would be through gleaning by local subsistence fishers and likely to have only a marginal effect on populations, unlike organised fisheries including recreational abalone fishing. Fur- thermore, while poaching has had a catastrophic impact on some commercial fisheries it is likely negligible on unexploited species. A digital distribution map accompanies each IUCN Red List species assessment. Maps were generated in ArcGIS (Environmental Systems Research Institute) based on occurrence records primarily following Geiger & Owen (2012) and reviewed by species experts [34]. To improve visualization at a global scale, maps were standardized using a base map for nearshore coastal species that extends to either the 200 m bathyline or 100 km from shore. For species of restricted range, the area within which the species occurs and whether it is contracting or becoming fragmented can be an important indicator in assessing extinction risk. From these species maps and for this summary, global maps of overall species richness, commercially fished species, and threatened species were generated in ArcGIS 10.8. For each of the three analyses, distribution maps were overlaid to determine the number of species occurring in

each 100 km2 grid cell. Fig 1 shows the global distribution of a) all species (n = 54), b) commer- cially fished species (n = 21) (note, some species may not be fished across their entire distribu- tion, especially where local regulations may include a size limit, or gear restrictions e.g., no SCUBA), and c) threatened species only (n = 20). Of the 54 species of abalone assessed globally, 20 (37.04%) are threatened with extinction, i.e., categorised as Critically Endangered (CR), Endangered (EN) or Vulnerable (VU), with a further three species categorised Near Threatened (NT). Fig 2 shows the number of species of each category by oceanic region. For further details refer to Tables 3 to 7 attached to regional analyses. Twenty-one of all abalone species (38.89%) are (or have been) commercially fished and/or are recognised targets of recreational fishers, of which 15 (71.43%) are categorised as threat- ened with one further species categorised as Near Threatened (NT). Of the 33 unexploited spe- cies, only five (15.15%) are categorised as threatened with a further two as NT. Fig 3 graphically illustrates that of those species with a sufficiency of data, i.e. not categorised Data Deficient, commercially exploited abalones are over four times more likely to face extinction as unexploited species. Analysis of conservation status by region In examining the abalone species by region, we divided the genus into five geographical sectors (total number of species shown in parentheses): Atlantic (6), Western Indian Ocean (10),

Indo-West-Pacific (15), Australasia (14) and Eastern Pacific (9). Some wide-ranging species may spill into an adjoining sector. Threatened species occur in every region (Fig 2) but the most species listed as Critically Endangered are in the Eastern Pacific along the western coast of the United States, Canada and Mexico. The analysis described below provides a summary of the principal issues in determining their category. Comprehensive referenced data on distribu- tion, populations and specific threats confronting each species, together with any conservation strategies that may be planned or implemented, can be found on the published IUCN Red List (iucnredlist.org) species records. 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 9 / 25