Effects of acclimation temperature and exposure time on the scope for growth of the blackfoot Pāua (Haliotis iris)

Context Climate change and increased seawater temperatures can greatly affect physiological processes and growth of marine ectotherms, including the blackfoot haliotid, Pāua (Haliotis iris). Scope for growth (SFG) is a laboratory-derived measure of the energy available for growth but this has not been examined in Pāua.Aims To measure SFG of seasonally collected Pāua and their haemolymph parameters at constant acclimation temperatures of 12, 15, 18 and 21°C for 28days.Methods Energy available for growth was measured from kelp food and losses due to respiration and ammonia excretion calculated on Days 1, 14, 21 and 28 of acclimation. Haemolymph parameters were also measured.Key results After 3days of acclimation, SFG was highly variable. Following 2weeks of acclimation, SFG was positive for all temperatures. Respiration and excretion energies depended on both acclimation temperature and time. Haemolymph parameters were affected by acclimation temperature.Conclusion Pāua have limited ability to acclimate to a temperature 21°C suggesting that they would not grow effectively at this temperature.Implications This research suggests that adult Pāua can be adversely affected by increased seawater temperature, resulting from climate change and this could affect their future growth and distribution.