If 25 years of experience with shrimp production has taught me (Dr Manoj M Sharma) anything, it is that rapid, unchecked expansion usually leads to rapid, devastating decline. As the managing director of Mayank Aquaculture Private Limited, I have been farming shrimp for more than two decades in India's second largest shrimp producing state, namely Gujarat.
Over that period, he has watched the growth of shrimp ponds in his area boom from one pond to 10,600 - as well as its decline due to rampant diseases affecting shrimp production.
Focusing his scope on Gujarat, Manoj expanded on the farmers shift from large scale Monodon production to producing Vannamei at an equally sizeable scale. "We were the first to talk about farming Vannamei the Monodon way because all our farms are equipped for 10 to 15 (m2) [Please check if correct measurement] stocking density and I was the first to practice Vannamei on the scale of Monodon. We even reached up to about 19 (m2) Vannamei in 2015 and 2016," he said. Gujarat's shrimp usually grew to a size range of between 30 to 45g but growth began to slow down in 2017, as Vannamei could not reach the 20 to 25g range. By the first half of 2018, 85% of ponds were affected by White Faeces Disease (WFD), EHP and Running Mortality Syndrome (RMS). It lead to a crash harvest of shrimp in the range of 15 to 20g.
In this case study Manoj experimented with his own farms in 2017 to better understand the issues of disease. He picked four different sites - an old pond with an old creek (OPOC); new pond, old creek (NPOC); new pond, new creek with high salinity (NPNC-HS); and a new pond, new creek with low salinity (NPNC-LS). All aspects from feed, stocking density, seed and protocols or farm management were constant, with the water source and location as the only variables.
Results from the OPOC showed slow growth with 140 days of culture (DOC) producing 36 to 40 count/kg with a 62.5% survival rate. "The FCR was very high, ending up at 1.8 because we started using biomass after every successful moult," he clarified. The NPOC showed an average growth with 133 DOC, producing 33 to 37 count/kg shrimp count with a 75% survival rate. While the NPNC-HS displayed slow growth with 155 DOC, but also yielded good production count of 40 to 45kg kg and a 90% survival rate. "Vannamei is not tolerant to salinity or temperatures above 32 degrees. But nothing happened to them even at temperatures that went up to 35 degrees because the water source was very pure," said Manoj. However the NPNC-LS exhibited super growth with only 105 DOC yielding 38 to 40 count/kg with a FCR of 1.15 and a 95% survival rate.
"The outcome of the case study was an eye opener. It very clearly showed that what matters is organic matter. The moment you have piles of organic load into the new incoming source, then you have problems," he said. Adding that shrimp health is directly related to water sources. "For the success of shrimp farming, it's now very clear to us, the pond carrying capacity versus the number of ponds over the creek is a detrimental factor.