1 DECEMBER 1999

Sent: November 23, 1999
From: Raul Coyula <coyula@fbio.oc.uh.cu>
To: <artemia-l@sparklist.com>

QUESTION:

Can anybody give me information on Artemia yields in cysts and biomass (kg/ha/month) for permanent solar saltworks? On which months can those yields be attained?

Raul Coyula

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COMMENTS :

Strictly speaking you should specify which strain/species of Artemia you are referring to. Yields can differ very very much depending on the strain as well as on where this strain is being inoculated.

I can give you following data (for a bisexual strain) which were obtained in a large permanent salt work in Egypt (1000hectares). Intermediate ponds (total culture area about 245ha) were inoculated at 5 to 10  nauplii/litre (in August). The first year we could collect 124.9kg WW  cysts (stop at end of December). The second year cyst yields dropped to 20kg WW ! We attempted several times to re-inoculate cysts, but with little success.

We also harvested 3 to 5 Ton biomass (WW/ha). Nevertheless, these biomass yields were not the maximum attainable. I mention here that primary production in those ponds was low and management not exactly optimal.

For Brazil I refer you to the article of Marcos Rogerio Camara and Renato de Medeiros Rocha. Artemia culture in Brazil : an overview; in: Artemia Research and Its Applications, Volume 3. Sorgeloos  P., Bengtson D.A., Decleir W. and Japsers  E. (Eds.). Universa Press. Wetteren, Belgium. 556p.
In this article yields of up to 30.8 Ton DW are mentioned for a 34,478ha for one year (in Rio Grande do Norte and Cenral) . However, note that after an initial success period total yields for Brazil also dropped quickly to 1.5Ton to 0.5Ton (for all Brazil) and most of the latter production came from artisanal salinas in Grossos (Rio Grande do Norte State, NE-Brazil) and in a couple of mechanized salt operations in Areia Branca (Rio Grande do Norte State, NE-Brazil). Two people who should be able to give you  more accurate information are Marcos Camara (mrcamara@ufrnet.br) and Vu Do Quynh (quynh_vudo@bigfoot.com), who probably are also connected to this list.

However, we (= me + staff of the Lab for Aquaculture & ARC together with my colleagues from the Institute of  Marine Aquaculture in Vietnam (sardictu@hcm.vnn.vn)) conducted some research studying
factors which influence cyst yields. One of our conclusions is that large
permanent salt works are not really suited to establish a sustainable cyst production system. After an initial success period, yields inevitably start dropping (as was the case in Brazil, Egypt, New Zealand, Tunisia).

Reason for this drop in production seems to be  a combination of :

1) the inability to keep your primary production high (= you can not
supply enough food to your females to assure big broods, a lot of broods and good survival and growth). To put this into ecological jargon, after appearance of the F1 (if you stock really low sometimes the F2) your populations reaches the upper limit of the carrying capacity of your ecosystem (= your culture pond), after which the
population reacts (decreasing broodsizes, increasing mortality, slowing
growth rate) and your cyst yields start decreasing. You could reason it is possible to increase the carrying capacity of your pond by adding food via other pathways, which indeed is possible. But 1) there are limits to what you can supply (ie to maintain high salinity keeping predators out, to prevent oxygen stress or to prevent completely destroying your pond bottom);
2) At the rates we stock the F1 is usually 20 to 200 times as abundant as the parental population (which we in fact already stock close to the
maximum carrying capacity of the pond), so even supplying food, your food given/animal decreases.

2) a selection towards ovoviviparity.

Although at this moment I am not sure there is proof there is a genetic
basis for "mode of reproduction", enough data at least indicate the ability to produce cysts is under some sort of genetic control. Assuming this is the case (which I do), you can be sure the ovoviviparous genome will start dominating the population, as ovoviviparous females reproduce much faster than oviparous
females (this can be mathematically proven using the "selfish gene theory" as written down by Dawkins and worked out by Maynard-Smith) and cyst yields will drop with each generation (which they do). However, if the complete population is killed off (during winter or when rains start or as in our case when re-stocking your ponds), the oviparous genome gets a chance to re-establish itself (as the new population per definition must start from cysts and it can be safely assumed these animals do carry the oviparity genome).

In Vietnam a number of systems were developed based on different principles which do tend to give high cyst production yields (Described in : Vu Do Quynh and Nguyen Ngoc Lam. (1987) Inoculation of Artemia in Experimental Ponds in Central Vietnam : an Ecological Approach and a Comparison of three Geographical Strains : 253 - 532. In Artemia Research and its Applications, Vol. 3. Sorgeloos  P., Bengtson D.A., Decleir W. and Japsers  E. (Eds.). Universa Press. Wetteren, Belgium. 556p, and Baert P., N.T. Anh, Vu Do Quynh,
NV Hoa and P. Sorgeloos (1997) Increasing cyst yields in Artemia culture ponds in Vietnam : the multi-cycle system. Aquaculture Research (28)  pp. 809-814). Farmers get on average yields of 25 - 30 kg DW/ha. 6 month season, but we at the station can get yields of more than 50kgDW/ha.season. (and are still improving this record). Systems are small (one farmer has between 4ha to 10ha) and are managed rather intensive. In most tropical and subtropical countries they can be set-up but besides environmental factors a number of socio-economic factors also have to be taken into account to develop the best suited system for a given region (the system with the highest yield is NOT always the most economic system).

So to be able to give you reliable estimates we will need to know :

1) What the weather is like in your place
2) What your preferred product is (biomass or cysts. If you choose
biomass, you still will have cysts but less)
3) Which strain you are considering for inoculation
4) What kind of culture system you had in mind

If you also like to know if your system will be sustainable we also need
information on:

1) Aquaculture business going + their demands
2) Local salaries
3) Skill and level of training of your local staff
4) Cost of permissions you need to import exotic species, culture them get land Peter Baert

E-mail: bpeter@hcm.vnn.vn

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