Developing shrimp reproduction techniques and learning at the laboratory scale: 1970-1980. Part 1

Reproduction in captivity from imported post-larvae

As there was not even one shrimp species of potential commercial interest present in the wild in Tahiti, Aquacop team began to work on Peneid shrimp with importing post larvae or adults from other countries. The first ones to arrive were some P. occidentalis adults, the survivors of a long trip on an oceanographic vessel from Panama to Mururoa, one of the Tuamotu islands in French Polynesia, 1 200 km from Tahiti, which they reached finally by plane from there. They died progressively but at least the team got the first live shrimp in one tank. Then, post larvae of P. japonicus and P. aztecus (from Cornelius Mock) were imported by plane.

In the same time, in New Caledonia, at a new R&D Station de St Vincent funded by the South Pacific Commission, Professor Doumenge was running the first shrimp grow-out in one earthen pond of 1 hectare with Francois Fallourd and Dan Popper, then with Michel Autrand, a geographer student of Pr. Doumenge. Alain Michel travelled to Noumea in order to participate to the first harvest, so happy to collect 20 kg of a mix species of P. Merguiensis, Metapeneus ensis, P. monodon and P. semisulcatus. They had been caught in the mangrove by trapping nets as juveniles and transferred to the pond. All these species were native of New Caledonia.

P. merguiensis and M. ensis were imported to Tahiti in plastic bottles where, thanks to some stewardess helping to regularly add oxygen during the flight from Noumea to Papeete. At the COP, they were transferred in a 400 m2 large rectangular tank lined with sheets of fiberglass of one mm thick, with a sand bottom and plastic drains linked together in a net with the inlet water flowing through from the bottom of the sand to the surface. This system was especially suitable for burrowing species like P. japonicus and M. ensis.

Shrimp eyestalk removal

At that time, Alain Michel was diving almost every day in the tanks to look at the behavior of the shrimp, based on his principle. “It is always of primary importance to look carefully at your animals every day. You cannot do aquaculture research only by looking at the screen of your computer and in fact, at that time, they were no computers. Looking at your animals allows you to prevent many problems before they become serious and to react quickly. The routine behavior of the shrimp is particularly informative”. Thanks to the specific clear water in the tanks, it was possible to follow the first batch of P. aztecus which were growing well and were reaching the adult size.

One of these days, Alain saw one female with developing ovaries clearly apparent under the cuticle from the head to the abdomen. He also noticed that one eye was missing probably lost at the molt. Two days later he found another female also with only one eye. There was a flash in his head, and suddenly remembered an old French publication about inducing the maturity in crabs by ablation of the eye peduncle, but also the negative conclusion of Charles Caillouet about eyestalk ablation in shrimp. Alain considered worth to try and the next day he cut with his nails the eyestalk on one side of seven P. aztecus females already with a white sperm mass in their closed thelycum. It was not very nice for the welfare of these shrimps but nobody at that time was taking care of shrimp welfare. In the next week they all spawned viable eggs. This is finally how Alain had found the right key to be able to go further on shrimp research in Tahiti where no local species were existing.

It was rapidly followed by the same result on P. merguiensis, P. japonicus, and M. ensis. It was published in 1975 in the proceedings of the World Mariculture Society held in Charleston.