Air survival in selectively-bred Greenshell mussels™ (Perna canaliculus): the influence of behaviour, aerobic and anaerobic metabolism.

Abstract

Perna canaliculus is the highest earning export product of the New Zealand aquaculture industry. In order to sustain and enhance this value, the New Zealand government and aquaculture industry are investigating the potential to add value to P. canaliculus by exporting them live. This exportation requires exposing the mussels to an aerial environment for a prolonged period of time as exportation in water is economically unfeasible. To successfully do this on a large scale, more knowledge about the physiology and behaviour of aerially exposed P. canaliculus is required as well as improvements in selective breeding programs. Accordingly, this thesis investigated the survival, aerobic and anaerobic metabolism and shell gape behaviour of selectively bred mussels from the Cawthron Institute. Initially, the research done in this thesis established the average survival time for each family (n=76) of P. canaliculus in the Cawthron Institute’s selective breeding program and from this nine families were selected to represent good, average and poor aerial survivors. From there, three characteristics of opine dehydrogenase activity, shell movements and oxygen consumption were measured within representative families and across all individuals over 14 days of aerial exposure at 9 °C and 94% relative humidity. The results of these experiments showed there are differences between selectively bred families in survival time (p<0.05). While there were differences between selectively bred families in the three characteristics measured, there was not a clear pattern in the characteristics according to survival ability. Across all nine families there were consistent patterns of changing levels of each characteristic over the period of aerial exposure. When the characteristic’s results were combined there was a pattern of three distinct time periods (days 0-4, 4-9, and 9-14). The outline of this pattern is initially low oxygen consumption and opine dehydrogenase activity that rises as time progresses while shell movement is the opposite. The implications of this study are that opine dehydrogenases, oxygen consumption and shell movements play important roles in aerial survival ability of P. canaliculus and that the live export of this species needs to consider the three different stages of physiology and behaviour when designing appropriate export methodology.