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

taxa such as abalones being expurgated. Sea urchin barren grounds for example, render areas that once supported abundant abalone populations devoid of algae and no longer able to sus- tain them resulting in a diminishing AOO [21]. Use and trade. Abalones have been fished by Indigenous peoples for millennia and hold special religious and cultural significance. Many local coastal communities have long traditions of subsistence fishing, a touchstone for community and family social events [60, 61]. Abalones are a valuable commodity, sought after for both their meat and shells and much prized as a del- icacy. High prices ensure there is a ready market for both legally and illegally fished animals, with poaching to some degree a recurrent issue within almost all abalone fished areas [54]. Although most fisheries are governed by regulation, enforcement is often patchy and it is com- mon for quotas to be exceeded or for closed fishery areas to be ignored. In addition to licensed commercial fisheries, active recreational fisheries will often be separately regulated with bag limits, numbers held and restrictions on resale. Threats. As may be seen in the regional assessments below, abalones are faced with a mul- tiplicity of threats, exacerbated by the biological requirement for individual animals to be in close proximity for successful reproduction [45]. General threats include poaching and over- fishing, habitat loss, MHWs, diseases including viruses, competition from sea urchins includ- ing kelp forest transitions to sea urchin dominated systems, pollution and predation.

Withering Syndrome, a fatal bacterial disease first observed in 1985 in black abalone (H. cra- cherodii) of California [62], has since spread to other abalone species initially within the same locality but subsequently through trade to other regions of the world, infecting both wild and cultured animals with mortality reported of up to 99% [26]. For the disease to be expressed, an infected abalone must be exposed to warm waters such as during an El Niño event to cause mortality [62, 63]. Future threats also include ocean acidification and general warming of the oceans from the combustion of fossil fuels. As shallow water species, warming seas can also have a direct impact on the primary food resource, algae. Conservation. There are many instances of conservation for species that have suffered from the effects of overfishing and the decline in abundance. To address these declines, res- toration programmes have been established, including MPAs, translocation of adults and captive breeding programmes. With the abalone aquaculture industry established in many countries, partnerships between aquaculture and fisheries in the form of restoration mari- culture may help bolster wild stocks and could be a critical feature for future conservation efforts [64, 65]. Synthesis and pre-publication checks Following our research and assessment, the results were reviewed by an international group of species and subject matter experts acting in a peer-review capacity, with each having a special- ised knowledge of those species they assessed. Owing to Covid-19 travel restrictions, the

reviews were primarily conducted by email and video conferencing in place of the custom- ary IUCN workshop scenario. The commercially fished species were reviewed by specialists both from within academia and also from government fishery authorities who undertake abalone stock assessments, establish catch quotas and liaise with anti-poaching enforce- ment. This peer-review process confirmed or modified findings of the original assessors and allowed inclusion of supplementary field-based knowledge from the participating experts. All reports were checked for consistency by the Mollusc Specialist Group of the IUCN Species Survival Commission before final approval and submission for publication through the IUCN Red List Unit. The assessments were published by IUCN in two tranches in the years 2021 and 2022. 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 8 / 25