Artemia was introduced in north-east Brazil in the late 1970s, and quickly dispersed through a large salt-producing area of more than 30,000 hectares in the neighbouring states of Rio Grande do Norte and Ceara.
In the first few years following its introduction, cyst harvesters exceeded 10 tonnes, representing total revenues of US$600,000 a year. Production has dropped more than tenfold since then, probably due to a combined effect of resource mismanagement, and environmental and genetic factors.
In recent years Brazil's north-eastern coast has also been experiencing a rapid development in marine shrimp farming. New enterprises, together with the intensification of culture metods and the switch from the local species Penaeus subtilis - whose post-larvae could be collected in the adjacent estuarine waters - to the exotic P. vannamei from Ecuador, have created a growing demand for post-larvae, supplied by new hatcheries.
The hatcheries are located in tropical, estuarine tidal plains which have been traditionally associated with salt production. But declining salt prices (around US$12 a tonne)have forced many small, artisanally operated salinas to shut down, and it is estimated that more than one third of that large salt producing area has been abandoned or underutilized, as the land is not suitable for agriculture.
With support from the Canadian International Development Agency (CIDA), trials have been conducted in the state of Rio Grande do Norte to examine the economic potential for the conversion of salt-production ponds into Artemia ponds using the semi-intensive culture methods first developed by staff of the Artemia Reference Centre in Belgium.
Brine shrimp culture does not require extensive water exchange, and no major modifications need to be made in the water supply system of a traditional salina. The most important structural change is the deepening of the pounds to avoid the lethal high temperatures that are found in salt evaporation pounds. These usually average 10 to 20 cm and have to be deepened to at least 40 to 50 cm, either by digging (if the pond is supplied exclusively by tidewater) or by raising the dykes (if pumping is considered). Internal wall of dykes are usually covered with palm tree leaves to avoid wind and water erosion. Artemia can tolerate wide fluctuations in environmental parameters and the only major concern in managing the system is to avoid the presence of predators, mainly fish (Poecilia, Aphanius, Mugil) and copepods. This can be done by careful screening of intake waters or simply, and much more effectively , by raising the salinity above their tolerance level, usually around 80 to 100 ppt.
For the trials seawater was pumped from an existing supply canal to a reservoir pond which was first fertilised using calcium nitrate. Water was then flowed by to the artemia ponds, which were inoculated with newly hatched nauplii.
Stocking rates were adjusted to natural feed availability which was supplemented using malt bran, a waste product from a local brewery. Final densities of around 60 individuals per litre and overall biomass production of more than 250kg/ha in the 15-day culture periods were achieved.
The short lifespan of the brine shrimp, reaching the adult stage in a few weeks after hatching, makes this a fast turnover system. Growth within the brine shrimp populations was fairly uniform. This enabled selective harvesting, during the 15-day cycles, to obtain individuals in the desired size ranges for use as live food in hatcheries.
Although the animals are cultured at very high salinities, they can be readily offered to the predators since their body fluids are maintained at low salinities.
These trials indicated the potential in this region to integrate Artemia production systems into the operations of fish and shrimp hatcheries. For a small investment live food can be produced on-site or close to hatcheries.
At current prices, conversions of salt-pans to Artemia production present an interesting alternative for salina owners, as 1 kg of live brine shrimp can be produced faster, in a smaller area and can be sold for the equivalent of two tonnes of salt.
(excerpts from article by S. Goddard and A. Alves Campos in Fish Farming International, December 1997, Vol. 24, No. 12)