Feeding technique, critical size and size preference of Jasus edwardsii fed cultured and wild mussels

This paper describes a technique used by juvenile red rock lobsters, Jasus edwardsii, 20–70 mm carapace length, to open and feed on live mussels. This technique appears to be an innate behaviour. The maximum or critical size (shell length) of cultured and wild Mytilus galloprovincialis, and cultured Perna canaliculus, which J. edwardsiiis capable of opening, is strongly correlated with lobster carapace length. Jasus edwardsii is capable of opening significantly larger cultured than wild M. galloprovincialis; this is a reflection of the differences in shell morphology between wild and cultured mussels, and the vulnerability of different shapes to the opening technique employed. In replacement experiments, the greatest numbers of mussels were eaten from the smallest mussel sizes (6–20 mm shell length), whereas the greatest amount of dry flesh weight was consumed from the middle mussel sizes (11–40 mm shell length) for all three mussel types. Dry-weight consumption was considered the most appropriate indicator of preference, the amount of mussel flesh consumed being more relevant to a rock lobster farmer than the numbers of mussels eaten. The preferred mussel size was approximately half the critical size. The application of these results to rock lobster farming is discussed.