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

Polynesia and the Pitcairn group. The remaining five species in this group are all fished com- mercially. H. discus (EN) with its subspecies, H. d. hannai (Fig 6) is the most extensively cul- tured species of abalone in the world, with major facilities in Japan, South Korea and Northern China as well as outside its natural distribution in places such as Chile, although here largely superseded by red abalone (H. rufescens) [74]. Despite the success of captive breeding for wild stock replacement, populations are in steep decline as a result of overfishing and the loss of habitat, in particular, its preferred species of brown macroalgae [75]. Its high retail value makes this species a target for poaching; although enforcement has been strengthened in Japan with severe penalties, it remains a serious issue [76]. H. gigantea (EN) has historically been consolidated with H. madaka (since accepted as a separate species), and there are no long- term unambiguous data on H. gigantea. Research into populations at its southern extent indi- cates extirpation caused by local loss of algae [77]. Although H. gigantea occurs sympatrically with H. d. discus and H. madaka, the total catch of H. gigantea alone is not distinguishable. It has been calculated that the total annual catch of all three species combined has declined dra- matically [78]. H. madaka (EN) was until recently considered a synonym of H. gigantea (see Table 4. Abalone species of Western Indian Ocean. Species Size C Distribution Cat mm Western Indian Ocean

H. alfredensis 79 Pondoland (Mbotyi) in NE Transkei to Port Alfred on Eastern Cape, South Africa DD H. arabiensis 40 N Salalah, Oman to N. Fujairah, UAE NT H. mariae 144 C S Oman (Dhofar) between Mirbat and Hassik EN H. midae 234 C N. Port St Johns on Eastern Cape to St. Helena Bay, Western Cape, South Africa EN H. parva 59 Coffee Bay on the Eastern Cape of South Africa to False Bay, Cape Town DD H. queketti 52 NE Somalia to Transkei, South Africa, also Mozambique—other reports questionable DD H. rugosa 63 Yemen and Red Sea to Park Rynie, South Africa, also Mascarenes and Madagascar LC H. spadicea 105 Northern KwaZulu-Natal to Partridge Point, Cape Peninsula, Western Cape, S. Africa LC H. squamosa 103 Madagascar: Lavanono to Fort Dauphin (Taolagnaro) DD H. unilateralis 40 N Red Sea and Oman to Eastern Cape of S. Africa and east to Mascarene Islands LC ‘C’ denotes commercially fished. https://doi.org/10.1371/journal.pone.0309384.t004 Fig 5. H. midae (EN). Occurs in South Africa. Victim of uncontrolled poaching. Reprinted under a CC BY license with permission from Buzz Owen, original copyright. https://doi.org/10.1371/journal.pone.0309384.g005 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 13 / 25