Nature - Populations Of Washington's Only Native Abalone Down 97% 1997 - 2017; Ocean Acidification Hitting Larvae Hard
Pinto abalone (Haliotis kamtschatkana), the only abalone species native to Washington, declined by 97% in the state from 1992 to 2017. Their decline is a loss for indigenous tribes, recreational divers, and the health of subtidal rocky reefs and kelp beds. Current restoration actions are facing threats of ocean acidification and warming in the northeast Pacific. This research aims to deepen our understanding of the tolerance and physiological flexibility of early life history stages of pinto abalone and inform hatchery practices under future climate change scenarios. We conducted an experiment to test how seawater pH and temperature stress impact abalone larvae. We exposed abalone post-fertilization to elevated temperature and reduced seawater pH for ten days spanning their larval development period: (1) 7.95pH/14°C (ambient), (2) 7.60pH/14°C, (3) 7.95pH/18°C, and (4) 7.60pH/18°C. Abalone in the ambient treatment had the best survival, those in the 7.60pH/18°C treatment had the worst survival, and those in the two single-stressor treatments had survival in between. Among the surviving larvae, pH was the dominant stressor influencing settlement success, with higher settlement rates under ambient pH treatments at both temperatures. pH also had a stronger effect than temperature on shell length. The information gleaned from this study is essential for optimizing future restoration aquaculture for pinto abalone and determining their ideal habitat and potential geographic range.
Pinto abalone (Haliotis kamtschatkana) are ecologically important grazers for the intertidal and subtidal ecosystems they inhabit and are prized for their economic and subsistence value1.While pinto abalone can be found from southeast Alaska, USA, to Baja California, Mexico, their populations have declined drastically along much of this range2. In Washington State (USA), pinto abalone experienced a 97% decline at 10 permanent index stations monitored for population trends from 1992 to 20173,4 and in 2019, they were listed as a state endangered species2,5,6.
Pinto abalone have historically been harvested to varying degrees by indigenous and non-indigenous people throughout their range2. While densities never supported a commercial harvest in Washington, their decline was noted; the State pinto abalone sport fishery closed in 1994, yet the population has not recovered3,7. The continued decline of pinto abalone could be caused by a combination of disease, illegal harvest, or changing water conditions, but the principal reason is their low population density1,3,8. The sparse distribution of reproductive adults hinders successful fertilization due to insufficient aggregation3. Gascoigne & Lipcius9, in their exploration of the Allee effect in marine ecosystems, emphasized that broadcast spawners and heavily exploited populations, both characteristics of pinto abalone, are particularly susceptible to exhibiting the Allee effect10.
Pinto abalone populations in Washington are unlikely to recover without human intervention. To rebuild the pinto abalone population to historic levels, hatchery-based restoration efforts were initiated two decades ago. These efforts have been led by the Washington Department of Fish and Wildlife (WDFW) and Puget Sound Restoration Fund (PSRF), with support from various other partners. Pinto abalone broodstock are spawned, and their gametes are combined to produce genetically diverse families. Larvae are raised through settlement competency, and juveniles are grown in nursery tanks for one to two years before they are outplanted to locations within the San Juan Archipelago and surrounding waters7.
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https://www.nature.com/articles/s41598-025-96605-3