White abalone (Haliotis sorenseni) was once known as the most delicate and delicious of the seven species of abalone that grow in the United States. Not coincidentally, in 2001, this snail — which ranges from Point Conception, California, to Baja California, Mexico — became the first marine invertebrate named to the U.S. endangered species list. Only a few thousand white abalone still live in the wild, and the population is decreasing at a rate of more than 10% per year.
The future of this species, Haliotis sorenseni, depends on captive breeding, but it will take decades to restore this species – a time period in which both ocean warming and ocean acidification will increase. This study investigated how breeding and stocking activities will be impacted by those changes.
The study found that the biggest factor in white abalone survival is temperature, so warming is a more pressing issue than acidification. Mortality in one-year-old white abalone increases significantly when water temperatures hit 18°C (64°F). For abalone that are exposed to Candidatus Xenohaliotis californiensis (CaXc), a bacterium that causes a disease known as withering food syndrome, those mortality rates increased even further. The study also found that water temperatures of 15°C (59°F) led to disease mortality — a lower threshold than identified in earlier work.
The study also analyzed genetic resilience in three maternal abalone families, work that revealed more hopeful results. One of the families studied showed much lower mortality rates, suggesting that by further studying genetics, managers might be able to produce abalone more likely to thrive in the wild.