Salinity responses of juvenile prawn Penaeus japonicus

Aquaflow Technical Leaflet 2003-133

European Network for the Dissemination of Aquaculture RTD Information (Q5CA-2000-30105) and previously FAIR-3837, URL: http://www.aquaflow.org/

In extensive aquaculture and in the stocking of Mediterranean brackish water lagoons with fluctuating salinities, salinity responses of juvenile prawn are of high importance. Within 48 hours, Penaus japonicus shows no mortality in a salinity range of 25-40ppt (parts per thousand) and a mortality of only 25-30% within a salinity range of 10-25ppt and 40-55ppt.

With a change in salinity from 37 to 10ppt, oxygen consumption increases rapidly to 300% of the initial value and stabilizes at 200% after a few hours. After the initial salinity conditions are restored, oxygen consumption remains raised for at least 6 hours. The calculated loss of productivity caused by a reduction of salinity under fluctuating conditions can amount to 33% of total animal weight. Crowding also increases oxygen consumption at stocking densities above 400 postlarval prawns/m².

In crustaceans, free amino acids (FAA) play an important role as intracellular osmotic regulators. The FAA of juvenile prawns were measured after 48 hours of exposure of the prawns to hypo- (<25ppt) and hyper- (>40ppt) osmotic stress. The concentrations of FAA decreased linearly with decreasing salinity from 50 to 10ppt. The highest amounts of individual FAA in seawater-adapted P. japonicus are exhibited by glycine (51%), followed by taurine (14%), arginine (10%), proline (9%), and alanine (6%).

The main osmoregulators are glycine, proline, and alanine, which together lower the FAA pool by 80% after hypo-osmotic shock from 40 to 10%. The concentrations of taurine, arginine, ornithine, and glutamate are not affected by external salinity change. Under hypo-osmotic conditions taurine, glutamate, and arginine decrease by only 13-15%, and aspartate, ornithine, and lysine by 28-34%. All other amino acids in the FAA-pool are reduced by 50 to 88% - the greatest loss being proline (by 96%). Below a salinity of 25ppt, intracellular volume regulation is maintained entirely by proline and glycine, whereas the other FAA concentrations remain more or less constant.

After hyper-osmotic shock, the concentration of nearly all FAA increase. This is also true for the essential FAA (+86%) – indicating protein hydrolysis. A salinity range between 25-40ppt is therefore recommended for the extensive aquaculture of P. japonicus.

For more information:

Josef Dalla Via
Institut für Zoologie und Limnologie der Universität Innsbruck
Technikerstrasse 25
A-6020  Innsbruck – Austria

Fax +43-(0)512-507-2930
E-mail: Josef.Dallavia@provinz.bz.it

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