I've been reading a number of papers on integrating Macrobrachium Rosenbergii into RAS (both "conventional" as well as aquaponics). Obviously, DO is a big issue in water quality but I also remember something about territorial behavior only allowing for stocking densities of about 2 adults per sqm. This seems to be in direct contrast to the stocking densities of 15 and more (though at reduced yields and FCR) referred to in other (short-term) studies. Can anybody provide an insight into what the actual limiting factor for stocking density here is? Thanks!
1) Water supply preferably from underground to provide unpolluted fresh and/or brackish water, pH7.0-8.5, temperature 28-31 degrees C, nitrite and nitrate levels < 0.1 ppm, with DO near saturation (common for all shrimps).
2) Males and females have different growth rates. Males show heterogeneous individual growth whereas females grow more uniformly. When stocked together at a high density, males show 3 distinct morphotypes: small male (SM), orange-claw male (OC) and blue claw male (BC). They are essentially territorial. BC males have the usualy long blue pereiopods, OC with shorter orange colored ones, and SM have slim translucent ones (just like those of females). BC is dominant over OC, and both suppress SM. OC will change into BC if BC is removed or when the OC grows larger than the largest BC in the tank.
3) Higher stocking densities can be achieved depending on the substrates provided in the pond or tank, e.g., some farmers place short lengths of PVC pipes. These substrates provide hiding places for newly moulted prawns (which increases survival and decreases cannibalism) and decrease fighting frequency (which reduces growth suppression). This would increase the number of OC and BC while reducing SM.
4) Another option is to practice monosex culture by grading ans sexing prior to separation into different ponds/tanks.
More details can be obtained from FAO's "Farming Freshwater Prawns" which I have attached (and which you most likely already have a copy).
Dear Gideon,
Thank you very much for that answer. So are you also saying that the fighting (as described under 3.) is the limiting factor? It appears like in that case an approach of PVC pipes on steroids (taking maybe a bunch of 1-2' x 3" pipes to create a kind of almost bee-hive like grow-out cage within a tank with water quality as mentioned above should be possible and allow for much much higher stocking densities than the 1-2 per sqm.
(Of course this does not look at any ethical considerations which need to be further evaluated to avoid ending up with the shrimp-equivalent of the worst type of factory farmed chicken... - at this point I am rather curious about what the actual limiting factor typically is, territorial behavior, aeration, other water quality factors, ...)
Agree to Gideon Khoo's answer. Unlike the marine shrimps,the freshwater ones are not that active & the growth rate is unequal. Aquaculturists
The PVC pipes placed in ponds and tanks provide hiding places for the prawns and prevent frequent contacts between males which result in fights and loss of appendages (reduction in market value). Under natural conditions, i.e., in the rivers and streams, there are lots of hiding places for the prawns, thus allowing them to grow to larger sizes as compared to high density culture.
Mud crab (Scylla spp.) farmers face an almost similar (and worse!) problem of fights between individuals (male vs male and male vs female) as well as cannibalism. In the South-East Asia, some farmers have developed plastic/PVC cages, stacked condominium style (or prison style), to house the mud crabs - 1 crab per cage. They are grown from crablet to marketable size adult stages in these cages.
From my brief experience, male-to male aggression and cannabalism seems to be a primary issue in the larger animals. Other than that they appear to be relatively robust to conditions.
Yes Kevin Green has given correct version other than environmental factors which are common to all, cannibalism should be managed for a better culture. In India, Andhra Pradesh state aqua farmers cultured these Macrobrachium successfully including hatchery. You can try to get reports from that area as a good reference.
You need to be aware in every life stage behaviour of this prawn, indeed the canibalism has started since the post larva stages and I think in the normal condition (good water quality and good feeding), avoid this canibalism is very critical. It can be done by providing a kind of shelter (from a smooth screen during PL stage and PVC or even bamboo for later stages) will useful to keep your prawn survive.