TEMPERATURE-DEPENDENT FEED CONSUMPTION PATTERNS FOR GREENLIP (HALIOTIS LAEVIGATA) AND HYBRID (H. LAEVIGATA x HALIOTIS RUBRA) ABALONE FED FRESH MACROALGAE OR A FORMULATED DIET

Because of the nocturnal and slow feeding activity of abalone, farmed abalone are typically provided with feed throughout the night. Understanding the nocturnal feeding patterns of abalone is fundamental to feed management and productive abalone farming. In this study, the apparent feed consumption for greenlip abalone (Haliotis laevigata) and hybrid abalone (H. laevigata x Haliotis rubra) fed fresh Ulva sp. or a commercial formulated diet at 18 degrees C or 22 degrees C were investigated at night. Abalone were exposed to low light intensity (3.4 Lux) from 7:00 AM to 7:00 PM and darkness from 7:00 PM to 7:00 AM. Abalone were fed to excess daily at 4:00 PM and feed intake was determined at 7:00 PM, 10:00 PM, 1:00 AM, 4:00 AM, and 8:00 AM. When Ulva sp. was added to the tank, greenlip and hybrid abalone immediately displayed a feeding response, which was not observed in abalone fed the formulated diet. Abalone consumed Ulva sp. at a linear rate from 4:00 PM to 8:00 AM. In contrast, the apparent feed consumption rate of abalone fed the formulated diet was minimal from 4:00 PM to 7:00 PM, and was highest between 7:00 PM and 1:00 AM. Apparent feed consumption rate of abalone significantly increased as water temperature increased from 18 degrees C to 22 degrees C, but the effect was greater for hybrid abalone compared with greenlip abalone. The total apparent feed intake of both greenlip and hybrid abalone fed Ulva sp. was significantly greater than for both types of abalone fed the formulated diet. The total apparent feed intake on dry basis, and nutrient intake for abalone fed Ulva sp. was significantly lower than for abalone fed the formulated diet. This study indicates that the upper temperature range for feed intake in hybrid abalone is higher than in greenlip abalone. Ulva sp. can stimulate abalone feeding, though the high moisture content in algae can reduce nutrient intake.