LC50 values for TAN and their 95% confidence
intervals for L. vannamei larval stages are shown
in Table 2. The 24-h LC50 for Z1 was 4.2 mg L1
TAN (0.6 mg L1 NH3-N); this increased with larval
development to 9.9 and 16.0 mg L1 TAN
(1.5 and 2.4 mg L1 NH3-N) for Z2 and Z3
respectively. Higher TAN LC50 were obtained for
mysis sub-stages, being 19.0, 17.3 and
17.5 mg L1 TAN equivalent to 2.8, 2.5 and
2.6 mg L1 of un-ionized NH3-N for mysis 1,
mysis 2 and mysis 3, respectively. The 24-h LC50
for postlarvae 1 was 13.2 mg L1 TAN and
1.9 mg L1 NH3-N. The recommended levels for
rearing zoea stages were estimated to be between
0.4 and 1.6 mg L1 TAN (0.06–0.24 mg L1
NH3-N). Mysis recommended levels were estimated
to be from 1.73 to 1.90 mg L1 TAN (0.25–
0.28 mg L1 NH3-N) and for PL1, values of 1.32
and 0.19 mg L1 for TAN and NH3-N were estimated
respectively