Determining the most appropriate feeding regime for the South African abalone Haliotis midae Linnaeus grown on kelp

Abstract

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 abalones 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.

Human-mediated drivers of change — impacts on coastal ecosystems and marine biota of South Africa

“…Since 1978, Ecklonia has been harvested for the extraction of a plant-growth stimulant and currently about 1 000 t wet weight of kelp is used annually for this purpose (Troell et al 2006). The proliferation of onshore abalone farms in the past decade created a substantial demand for fresh kelp fronds as feed and, as a consequence, the harvesting of fresh-growing kelp has become increasingly important (Troell et al 2006, Francis et al 2008. Annual totals of 5 000-6 000 t wet weight of fronds are currently harvested, mainly where abalone farms are concentrated on the West and South-West coasts (Troell et al 2006).…”

Effects of wild and farm-grown macroalgae on the growth of juvenile South African abaloneHaliotis midaeLinnaeus

“…With the expansion of the abalone industry in recent years, the demand for fresh kelp has steadily grown , Francis et al 2008a). In 2003, more than 7000 tons of fresh kelp fronds were harvested (Robertson-Andersson et al 2008).…”