Short CommunicationGrowth of post-weaning abalone Haliotis midae fed commercially available formulated feeds supplemented with fresh wild seaweed

The effect of five formulated feeds supplemented with fresh wild seaweed on the growth of post-weaning juvenile abalone Haliotis midae (6–20 mm shell length) was investigated by means of a growth trial at a commercial abalone farm over a period of 11 months. The experiment included 10 diet treatments with two replicates each (n = 50 individuals per replicate). The first five diet treatments comprised four fishmealbased formulated feeds: Abfeed®, Adam & Amos® ‘a', Adam & Amos® ‘b' and Adam & Amos® ‘c'; and an all-seaweed-based formulated pellet, FeedX. The additional five diet treatments comprised the formulated feeds above, supplemented with fresh wild seaweeds: the kelp Ecklonia maxima (5–15% protein) and Ulva lactuca (3.7–19.9% protein). The fishmeal-based protein feeds produced significantly better growth than the all-seaweed-based protein feed (FeedX: 0.49 ± 0.03 specific growth rate [SGR]; 27.15 ± 0.02 daily increment increase in shell length [DISL]; 0.864 final condition factor [CF]). Abfeed® (1.00 ± 0.02 SGR; 60.79 ± 0.04 DISL; 1.312 final CF) performed best of all the formulated feeds. Supplementation with fresh, wild seaweed, however, significantly improved growth of all abalone with supplemented Abfeed® (1.05 ± 0.02 SGR; 63.61 ± 0.05 DISL; 1.447 final CF), outperforming all supplemented feeds. A noteworthy observation was that the condition factor of abalone fed the feed that performed particularly poorly in the growth trials (FeedX) was dramatically improved by supplementation. It was shown that supplementation with fresh wild seaweed enhances the growth of abalone reared on formulated feeds.Keywords: Abfeed®; Adam & Amos®; diet; formulated feed; growth; Haliotis midae; seaweed; supplementationAfrican Journal of Marine Science 2008, 30(1): 199–20