Comparison of diets for the tropical spiny lobster Panulirus ornatus:: astaxanthin-supplemented feeds and mussel flesh

The fast-growing tropical lobster Panulirus ornatus is a good aquaculture candidate generating increased research to develop potential feeds. We conducted a 12-week experiment, assessing growth, survival and tissue carotenoid levels of juvenile P. ornatus. Lobsters were fed either pelleted feeds supplemented with astaxanthin and containing 30, 60, 90 or 120 mg total carotenoid kg(-1); or one of two fresh mussel reference feeds - blue Mytilus edulis and green-lipped Perna canaliculus. There was no clear dose response, in terms of growth rate, to increasing dietary astaxanthin content; mussel-fed lobsters had inferior growth rates. Twelve-week survival was unaffected by treatment. Whole lobster carotenoid (4.7, 16.7, 27.8 and 32.8 mg kg(-1), dry matter basis) increased with increasing dietary astaxanthin; pre-treatment carotenoid was 22.2 mg kg(-1). Apparent total carotenoid content of the mussel-fed lobsters was unexpectedly high because of interference by other pigments. High-performance liquid chromatographic analysis of free astaxanthin levels varied from a pre-treatment value of 7.3 mg kg(-1) to 2.0, 7.6, 12.5 and 23.6 mg kg(-1) with increasing dietary astaxanthin, and 3.5 (green-lip) and 5.9 (blue) mg kg(-1) for the mussel-fed lobsters. Although dietary astaxanthin, over the investigated range, did not affect growth rate or survival, there was a dose-response increase in tissue carotenoid content and darkening of the exoskeleton pigmentation, which may have important implications for immunocompetency and marketing. These implications are discussed in the context of pelleted feed development for this species.