Physiological basis of inter-population, inter-familiar and intra-familiar differences in growth rate in the green-lipped mussel Perna canaliculus

Scaling parameters were also determined for metabolic rate, clearance rate, and gill-surface area in the two wild populations of mussels, for comparison of the allometry of the populations, and for size standardization of data. No significant inter-population differences were found in the scaling exponent for any of the parameters, indicating that the size-dependency of physiological rates was effectively the same for mussels from the different geographic areas. However, in contrast, significantly different mass-specific clearance rates were seen in mussels from the two different populations, indicating enhanced energy balances for mussels derived from the Golden Bay population. In the inter- and intra-family experiments, significant differences were found between fast-growing and slow-growing mussels both in terms of anatomy (condition index and relative size of the digestive gland), and in physiological traits such as clearance rate, routine metabolic rate, scope for growth, growth efficiency and metabolic costs of feeding and growth. These results point towards a relatively higher food processing capacity in the gut of faster-growing mussels, and a generally higher metabolic cost of feeding and growth in slower growing mussels. Overall these results reveal the strength of the genetic factors in determining inter-individual variations in physiological performance affecting growth potential, and reinforce the notion that selection of breeding stock both with regard to origin or family provides considerable scope for improvement in mussel production.