In order to increase the cyst production in the ponds 35, 36, 37 … an eradication of the papalote should be achieved, because these ponds are in the final stage of the salt production, the flow is lower, and we control the water entrance.
The solution(s) is (are) not easy to define, due to the lack of data on the animal biology. The different (cheap, easily adaptable to the local conditions), ways are listed here.
Observations and hypothesis, chemical eradications, mechanical fences, are developed.
As described before (see in B. MENU 88), we observed there is a strong difference between the pond 34 and 35. The modification happens just after the pumping station.
A strong presence of the papalote in pond 34 ≠ Its low presence in pond 35.
It seems possible to think that the pumping affects the papalote and its development in pond 35.
We need to check if the pumping affects mechanically the papalotes.
Is the papalote weakened above a certain salinity ?
Does the pumping affect selectively the fish, eggs, juveniles, adults, gravid females? No numbers are available on the amount of papalote coming in pond 35, This should be checked.
One other hypothesis is that a little pumping cavitation kills the papalote, by the presence of nitrogen over saturation, this should be inquired further, and if it could be optimize in some way, it will solve much time and efforts.
If we assume the pumping of both stations is similar, the pumping from F.P. 1 should affect the fish in the same way.
As reported by B. MENU a very large population of papalote is brought in, from F.P. 1 through the pipe line and proportionally many of them are alive.
Is the pumping (P3) similar in quality and in running?
In the meantime some other aspects of the eradication must be investigated.
All of them are linked to the knowledge of the animal biology.
It has to be known as soon as possible.
Just to be able to raise them in the laboratory in an aquarium will help a lot and fast, to know its growth, resistances to the salinities of the fish and the eggs, sizes of the eggs…, their diets, their Artemia consumption (size)?
There is a plant (Agave sp.) in Cuba (in fact in both American Continents), which contains a fish killing substance. The Spanish name is Maguey (see Pictures # 15), its use, advised by Mr. VU DUNG from Vietnam (Jan. 1990), was effective on the papalote but absolutely no information is available on that toxin at the MIP.
It is used now at the level of 10 gr. of plant per m3, by throwing them as 5 cm squares cut leaves in the ponds.
Beside the waste of efficiency, this level of use seems totally impractical: for a pond of 30 ha of 30 cm depth, we will need 9 metric tons of plants. It does not seem to be economically feasible, so we try to know the minimum activity efficiency of the Maguey.
The ratio juice and fiber has been determined.
About 200 gr., parts of a leaf of 40 cm wide, have been crushed in a mortar, squeezed through a fine nylon mesh (125 μm.): a minimum of 137 ml of a very dark juice has been extracted, This gives us a ratio of min. 70% of juice, but the conditions were far away to be perfect and some losses occur.
(the residue of 60.6 gr. of fiber has been soaked for a night in 50 ml tap water and a second extraction was done which appears less concentrated.)
In the laboratory we tested the toxicity of the Maguey juice on 1,5 to 2 cm juvenile papalotes. At 25 ppm (1 drop in 2 liters) the toxin kills all the fish in less than 3 hr. If this level is near the reality, it will be possible then to cure a pond of 30 ha with less than 100 liters or 200 Kgr of leaves.
These tests must be redone in better laboratory and field conditions to define the eventual use of the Maguey. Size of animal/concentration of the Maguey?
Before to use it on full routine practice on the ponds, which are linked to human food products, salt on one side and white shrimp though the eggs of the Artemia on the other side, it is necessary to enhance the data on the toxin.
Here is a list of some basic information needed.
Plants and toxin identification, literature?
Activity of the toxin, neural, muscular, through gills?
minimum activity by dilutions, dl 50,
remnant, in algae, in shrimp,
sensibility, oxidation, Antagonisms or synergy with other products,
Degradation in an another toxin,
Bio essays on fish larvae and white shrimp, fish fed with algae and brine shrimp biomass, cysts produced in treated ponds,
Toxicity for human and other animals.
If the answer of the biological “safety” will conclude to a positive possibility of using the Maguey in the Artemia ponds, then the local availability will arise. To save on the local resources its use will have to be optimized.
Here too, is a list of some basic information needed.
Culture of the Maguey, speed growth of the plant.
Maximum extraction of the toxin.
Reuse of the fiber in the water inlet net.
Study the conservation, for storage and transport.
We want to remove as much as possible of papalotes, a small fish, envading the salt flats above 80 gr./l. of salt in order to increase Artemia population and in consequence Artemia cysts harvest.
In some places the water is pumped, in large flow. In comparison we have to remove very few, and small particles (down to the size of egg papalote).
We have 1 or 2 meters height waterfalls at the pipe line exhaust and at the no 35 pond pumps (P4).
We have a continuous flow through the gates on all the salt ponds.
We need minimal maintenance and self clearing devices.
Because we can not avoid the presence of papalote in the large evaporation pond areas and waiting that its biology is better known, we can try to keep its population down as much as possible by:
as the water is transfered from one pond to the other
The vertical screen is in use in many industries around the world, because of the harsh environment (salt and sun) the screen must be build with non corrosive materials, plastic frame and polyethylene mesh (not nylon). The mesh size will stop the papalote eggs and will have as an another advantage to stop algae coming in the ponds. In return a cleaner harvest of eggs could be expected
The gate traps (see Drawing 2)
Traps in the salt pond will have to be tried as we do not know the behavior of the papalote in the salinas. The few times we were able to see them, we observed that they school, so it might be possible to concentrate them, and then it will be easier to use the Maguey.
