Breeding and larval feeding behaviour in the common Sydney octopus, Octopus tetricus

Abstract

Over the last 30 years limited advances have been made in the larval culture of merobenthic octopus species, with the successful rearing of paralarvae until settlement and beyond remaining a rarity. The low survival of reared paralarvae remains the main limiting factor for the development of octopus aquaculture globally. Successful rearing attempts have used zoeae of different crab species as feed but obtaining sufficient amounts of zoeae reliably will be challenging and most likely too labour intensive for commercial octopus hatcheries. The research presented in this thesis aimed to increase knowledge on the breeding and paralarval feeding behaviour of O. tetricus and evaluate its potential as a candidate species to diversify aquaculture in New Zealand. Experiments conducted in this thesis show that it is possible to achieve high survival of eggs reared in artificial rearing systems. Morphometric assessments of embryos and paralarvae incubated in constant temperature experiments showed complex interactions of brood and temperature and indicated that maternal effects significantly affect the quality of embryos and paralarvae. The lipid and protein content of paralarvae did not vary among different incubation temperatures (16-25 °C) despite a tendency of the inner yolk of late eggs and paralarvae to be lower with increasing rearing temperatures. In contrast, protein content of paralarvae from the same brood decreased with hatching time and starving period. The fatty acid profile of O. tetricus paralarvae showed similarities to other octopus species, i.e., high palmitic, stearic, DHA and EPA content. Paralarvae feeding experiments showed that artificial rearing does not negatively affect seizure success of paralarvae. Moreover, formulated pellets were readily captured and therefore have the potential to be developed as an alternative to live prey if palatability, handling characteristics and nutritional composition of these diets can be matched to the requirements of paralarvae. The results of this research provide the first step towards developing O. tetricus aquaculture by characterising the breeding and paralarval feeding behaviour. However, more studies are required to determine the nutritional requirements and key environmental conditions to achieve high paralarvae survival until the sub-adult stage, which is key for the establishment of a successful octopus aquaculture industry in New Zealand.