Thermal preference and tolerance of green abalone Haliotis fulgens (Philippi, 1845) and pink abalone Haliotis corrugata (Gray, 1828)

The thermoregulatory behaviour of green abalone Haliotis fulgens and pink abalone H. corrugata was investigated. Haliotis fulgens juveniles ranging in wet weight from 3.0 to 3.3 g and from 28.7 to 30.5 mm shell length and of H. corrugata 2.0 g and 25.7 mm in shell length were exposed to 19 degrees C for 30 days in a flow-through water system. Temperature preference was determined in a horizontal thermal gradient and was found to be 25.4 degrees C for green abalone and 25.0 degrees C for pink abalone. Displacement velocity was 4.3 cm h(-1) for H. fulgens and 12.8 cm h(-1) for H. corrugata. The optimum temperature for growth calculated for both abalone species was 24.6 and 24.5 degrees C respectively. The critical thermal maxima (CTMax) of H. fulgens and H. corrugata were determined as a measure of thermal tolerance. Abalones were subjected to increasing water temperatures at a rate of 1 degrees C on 30 min until they detached from the substrate. The CTMax at 50% were 33.6 and 32.0 degrees C for green and pink abalone respectively. The results are discussed in relation to site selection and commercial rearing.