The effects of temperature, age, and acclimation to salinity on the survival of Farfantepenaeus paulensis postlarvae

Salinity tolerance limits during the ontogenetic development of Farfantepen aeus paulensis postlarvae (PL) were determined at different temperatures. I nitially, PL 10, 20, 30, 40, 60 and 80 maintained in 30 pot (parts per thou sand) salinity, 22-25 C, were directly transferred to 15 combinations of sa linity (2, 5, 10, 20 and 30 ppt) and temperature (15, 20 and 30 C) for 96 h . Irrespective of age or salinity, higher survival rates were registered at 25 C, PL 10 suffered high mortality, especially at low salinities combined with low (15 C) or high (30 C) temperatures. From PL 20 to PL 40, an incre ase in survival was observed in all combinations. For PL 60 and 80, toleran ce to low salinity was reduced, suggesting that PL have a maximum age by wh ich they are able to develop adaptability to low salinities. In general, th e effect of temperature contributed more significantly to mortality in PL 1 0 and PL 30, but its influence decreased afterwards. From PL, 40, salinity becomes the main factor determining mortality. In order to examine the effe cts of acclimation to salinity on the tolerance limits, a second set of exp eriments was performed with PL 5, 10, 15 and 25 acclimated to 2, 5, 10, 20 and 30 ppt, 25 C, over a 5-d period. Postlarvae were then transferred to di fferent salinity levels (2, 5, 10, 20 and 30 ppt) and kept for 96 h. High m ortality of PL 10 occurred after direct transfer from high to intermediate/ low salinity levels. Although the acclimation to salinity increased surviva l, it was still Door. An increase in the salinity tolerance was observed fr om PL 15 to 30, even with no acclimation. Results indicate that PL 10 do no t have a fully developed osmoregulatory capacity to cope with low and/or ab rupt changes of salinity. It is recommended that non-acclimated PL 10 shoul d only be released in environments with salinity at or above 20 pot. If acc limation is carried out, PL may be released in salinities above 10 ppt. The release of PL 10 in salinities below 5 ppt may result in mortality rates o f up to 70%. The best age for the release of non-acclimated F. paulensis PL in environments with low and, or wide fluctuations of salinity would be PL 15-30.