Release of green tiger shrimp (Penaeus Semisulcatus) seeds in Palk Bay through sea ranching by Mandapam Regional Centre of Central Marine Fisheries Research Institute (CMFRI) has helped in replenishing the species and benefited fishermen, if the quantum jump in the catch is any indication.
After observing drastic depletion in shrimp resources in Palk Bay due to ‘over fishing’ of brooders (parent shrimps) and juveniles, CMFRI launched sea ranching in 2017 as part of its societal initiative and found that the programme has immensely benefited the fishing community.
After releasing more than 70 lakh shrimp seeds, including 12 lakh during 2019-2020, CMFRI conducted an impact study in June and found that the quantum jump in the catch of green tiger shrimps on the first three days of the new fishing season, which began on June 16 after the end of a 61-day ban period, was due to sea ranching.
Giving details of the catch, R. Jayakumar, scientist in-charge, CMFRI, said green tiger shrimp constituted close to 70% of the total catch in the new season and correlated with the sea ranching programme. The shrimp catch on the first day was 800 kg to 1,000 kg per mechanised boat compared to 250 kg per boat earlier.
Increase in natural stock and largescale migration after drastic climatic change could be attributed for the huge catch, but there was no major climatic change in the post-sea ranching programme. Preliminary studies showed that the sudden increase in stock of green tiger shrimp was due to the programme.
The second day catch was 500 kg to 600 kg per boat and the jump in the catch was witnessed up to Kottaipattinam in Pudukottai district.
CMFRI, which possessed parent DNA of the released shrimp seeds, collected landed shrimps for analysis. Scientists had completed the first level of analysis and expected to complete the second in a month.
“Preliminary level analysis, however, indicated that more than 40% of the catch was from our stock,” Mr Jayakumar said.
CMFRI achieved higher survival rate in sea ranching against the global average of 4% to 7% as it released the seeds in sea grass bed areas. This helped the seeds to get feed from the sea grass bed and protection from predators.
CMFRI produced a seed at the cost of 10 paise, but it fetched Rs 4.15 per shrimp to the fishermen. Although there was no separate funding for the programme, CMFRI launched sea ranching as a societal initiative and would continue the project for the benefit of the local fishermen, he added.