Browsing by Author "Francis, Tamson"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Determining the most appropriate feeding regime for the South African abalone Haliotis midae Linnaeus grown on kelp
    (Springer Verlag, 2008) Francis, Tamson; Maneveldt, Gavin; Venter, Jonathan
    Beach-cast kelp (the most widely used feed for commercially grown South African abalone) is plentiful during winter months when periodic storms cause kelp to wash ashore. During summer, however, this resource is not always readily available and farmed abalone are often starved for short periods. The aim of this research was to assess how periodic kelp starvation influences growth of the commercially grown abalone, Haliotis midae Linnaeus. Growth of grow-out abalone was monitored on a commercial abalone farm over a period of six months and consisted of 3 treatments with 2 replicates (n = ±250 abalone per replicate). The treatments were: Control (abalone always given more kelp than what they typically needed); Treatment 1 (abalone fed their weekly ration only once a week); Treatment 2 (abalone fed half their weekly ration every 3 and then 4 days respectively). While the data at first suggest that the control animals outperform the treatment animals, after undergoing an initial adjustment period to the new feeding regime, the treatment animals perform better. Weight gain and feed conversion efficiencies show that the treatment animals perform better overall. The control animals generally required much more feed to produce comparable increases in both length and weight compared to the treatment animals. This study has shown that periodic bouts of starvation is beneficial to Haliotis midae, allowing variable growth spurts when returned to full feed rations.
  • Thumbnail Image
    Item
    Growth of market-size abalone (Haliotis midae) fed kelp (Ecklonia maxima) versus a low-protein commercial feed
    (Taylor & Francis, 2008) Francis, Tamson; Maneveldt, Gavin; Venter, Jonathan
    The growth of grow-out abalone fed on kelp, with ca. 10 % dry weight protein content, was compared with that of those fed a new ,ca. 26 % protein, commercial feed in a flow-through system on a South African west coast commercial abalone farm. While both feeds produced similar gains in shell length (45.220 μm.day-1 for kelp, 46.839 μm.day-1 for commercial feed), the latter significantly outperformed kelp in terms of weight gain (0.266 % body weight.day-1 for commercial feed; 0.257 % body weight.day-1 for kelp). This low-protein commercial feed may prove to be of considerable benefit as substitute for the kelp plus high-protein feed sometimes used for abalone, because it has most of the benefits of the two feeds, but none of their apparent disadvantages.