The influence of flesh ingredients format and krill meal on growth and feeding behaviour of juvenile tropical spiny lobster Panulirus ornatus

One of the main challenges for spiny lobster aquaculture is the successful development of formulated feeds that are attractive, readily consumed by lobsters and promote optimal growth and survival. In a 54-day growth trial, we investigated the performance of four moist formulated feeds containing A) non-homogenised flesh ingredients; B) fish meal only; C) 10% krill meal; or D) homogenised flesh ingredients; and a reference diet of shucked blue mussel (Mytilus galloprovincialis) flesh, on growth, nutritional condition and feeding behaviour of juvenile tropical spiny lobster (Panulirus ornatus) reared either communally or individually. Growth and survival achieved by lobsters fed mussel were significantly higher than all other treatments. However, lobsters fed the formulated feed containing 10% krill meal (treatment C) and reared communally had a significantly higher growth, survival and feeding performance when compared to the formulated feeds with inclusion of non-homogenised and homogenised flesh ingredients (treatments A and D). The highest levels of feed interaction and pellet consumption among the formulated feeds were also recorded for treatment C. We demonstrated that the inclusion of krill meal in formulated feeds provides a benefit when compared to the inclusion of the flesh ingredients. Flesh ingredient format (homogenised or non-homogenised) had no effect on growth performance of lobsters, suggesting that the process of homogenisation of flesh ingredients does not provide any benefit in promoting feed consumption. Furthermore, time-series photography analysis trials showed that all the formulated feeds only promoted a feeding response within the first 2-3 h post-feeding, whereas mussel retained its attractiveness throughout the feeding period. These results suggest that the prolonged attractiveness remains an impediment for formulated feed performance in lobster culture. The present study also showed that growth performance and feeding response were higher in lobsters reared communally than individually. As observed in other spiny lobster species, it is likely that social interactions in communal housing may have provided cues that stimulated feeding responses and promoted higher growth rates.