Performance of Penaeus paulensis (Perez-Farfante) broodstock under long term exposure to ammonia

The effects of total ammonia (TAN; NH4+ + NH3) on the reproductive performa nce, survival, growth and moulting of wild Penaeus paulensis (Perez-Farfant e) broodstock were studied to determine optimal rearing conditions, Based o n previously established 'safe levels' for P. paulensis adults (3.4 and 4.2 mg L-1 TAN), two 46-day trials were performed. In the first trial, six fem ales and four males were stocked in 700-L tanks under three treatments (0.3 7, 2.53 and 6.86 mg L-1 TAN) with at least two replicates per treatment. In trial 2, ammonia levels of 0.68, 1.55 and 2.62 mg L-1 TAN were assigned to three 6000-L tanks, each stocked with 36 females and 24 males, Ammonia onl y influenced the survival of females and the growth of males exposed to 6.8 6 mg L-1 TAN (0.21 mg L-1 NH3). No further effects of ammonia on moulting a nd reproductive performance were detected, The present results demonstrate that up to 2.62 mg L-1 TAN, coupled with 0.07 mg L-1 NH3 and 1.50 mg L-1 NO 2, will not impair reproductive performance of P. paulensis. It is suggeste d that water quality for the maturation of P. paulensis may be maintained t hrough lower daily water exchange rates instead of the usual high levels (1 50-300%) employed on penaeid shrimp maturation systems.