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, J asus edwardsii, 20-70 mm carapace length, to open and feed on live mus sels. This technique appears to be an innate behaviour. The maximum or critical size (shell length) of cultured and wild Mytilus galloprovin cialis, and cultured Perna canaliculus, which J. edwardsii is capable of opening, is strongly correlated with lobster carapace length. Jasus edwardsii is capable of opening significantly larger cultured than wi ld M. galloprovincialis; this is a reflection of the differences in sh ell morphology between wild and cultured mussels, and the vulnerabilit y of different shapes to the opening technique employed. In replacemen t experiments, the greatest numbers of mussels were eaten from the sma llest 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 wa s 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 appro ximately half the critical size. The application of these results to r ock lobster farming is discussed.