1 JUNE 1999
USE OF ARTEMIA FOR CLARIAS GARIEPINUS LARVICULTURE
I've worked quite a time on larval rearing of this species and in the Netherlands we have a small but flourishing industry raising catfish.
There is a difference in what the industry does and what biologically is feasible. We can feed the larvae without Artemia from the start of exogenous feeding onwards, however at the expense of a considerable growth loss. According to my data, you need to feed them with Artemia up to an average individual weight of 50-60 mg, i.e. about 1 week. However, our commercial hatcheries do not take the risk and feed them with Artemia for a full 2 weeks (i.e. until a size of 100-150 mg).
Then they gradually wean them onto a dry diet in a period of max. 1 week again. Weaning can be done in 3-4 days. The commercial hatchery uses Nippai or an equivalent nursing diet as the weaning diet. Our data show that indeed it is better to wean to such a diet rather than to a crumble of juvenile trout diet; f.ex. feeding this weaning diet can continue for another 10-14 days at maximum (total feeding period: one month) (up to a size of 300-500 mg). At that age they should be transferred to a normal juvenile diet (e.g., Trouvit 000). Fingerlings are sold at a size of about 10 g. During the last period (between 0.5 and 5-10 g), feeding should be restricted to avoid occurrence of the ruptured intestine syndrome; growth rate is then not maximised but survival does.
The amount of Artemia feeding in commercial hatcheries is simply stated as: "as much as possible, during the whole day and night". What they do is "drip" feeding of Artemia (continuous) at a rate that there is always a surplus in the tanks.
In our experiments we standardised our work schedule by feeding them 5 times during daytime (which is not the best: they eat most in the morning and the evening). Also we feed them to satiation but we calculate more or less the amount of dry matter of Artemia to be fed for satiation feeding (this is more as a safety rule that we standardise our experimental conditions rather than a finetuned feeding ration estimation). The way of calculation is published in Aquaculture 1987, nr. 63 (special issue on Clarias).
No, we never feed enriched Artemia. Best procedure is just hatched
nauplii, and keeping them cool during the daily feeding period.
Dr. Johan A.J. Verreth
Associate Professor
Fish Culture & Fisheries Group
Wageningen Institute of Animal Sciences (WIAS)
Wageningen Agricultural University
POBox 338, 6700 AH Wageningen, The Netherlands
voice: - 317 - 48 3307 or 48 3510
fax- 317 - 48 3937
http://www.zod.wau.nl/venv/index.html
Johan.Verreth@ALG.VENV.WAU.NL