Thermal Preference and Tolerance of the Black Abalone Haliotis cracherodii (Leach 1814) (Gastropoda: Prosobranchia)

Abstract: Haliotis cracherodii is the only abalone species listed as critically endangered (IUCN Red List) and protected under the Endangered Species Act (ESA) since 2009. The population started decreasing in the mid-1980s throughout its biogeographical range due to the “withering syndrome” disease. The objective of this study was to evaluate the thermoregulation of the black abalone, establishing its preferred temperature, locomotion displacement, and critical thermal maximum (CTMax). The preferred temperature (PT) was 13.8 °C. The theoretical temperature for optimal growth of the black abalone was 14.3 °C. The locomotion displacement in the gradient had an interval of 137 to 83 cm h–1. CTMax was evaluated, the first abalone detached from the substrate at a temperature of 25.4 °C and the last one at 31 °C; CTMax of 50% was calculated at 29.7 °C. These data will allow us to maintain and condition the black abalone in captivity with the final goal of producing seed for the restoration of disease-impacted populations on the Baja California Peninsula. ENSO events may also affect the survival of black abalone. We extrapolated the Thermal Safety Margin (TSM) = (28.8 – 18.31 °C) = 10.49 °C in weak ENSOs, but in stronger ENSO the TSM value diminishes to 3.17 °C suggesting that black abalone may be vulnerable to climate change.