performance of
Wssv-infected and wssv-negative penaeus monodon postlarvae in culture ponds
S.E. Peng, C.F. Lo, S.C. Lin, L.L. Chen, Y.S.
Chang, K.F. Liu, M.S. Su, G.H. Kou-2001
Diseases of Aquatic Organisms, 46(3): 165-172
Abstract:
In a survey of 27 Penaeus monodon culture
ponds stocked with postlarvae (~PL10) at medium density (~40 shrimp m-2),
single-step nested white spot syndrome virus (WSSV) PCR was used to measure
the WSSV infection rates in the shrimp populations within 1 mo after
stocking. Seven ponds were initially WSSV-free, and the shrimp in 5 of these
were harvested successfully. In the ponds (n = 6) where detection rates were
higher than 50%, mass mortality occurred during the growth period, and none
of these ponds was harvested successfully. In a subsequent study, P.
monodon brooders were classified into 3 groups according to their WSSV
infection status before and after spawning: brooders that were WSSV-positive
before spawning were assigned to group A; spawners that became WSSV-positive
only after spawning were assigned to group B; and group C consisted of
brooders that were still WSSV-negative after spawning. WSSV screening showed
that 75, 44 and 14%, respectively, of group A, B and C brooders produced
nauplii that were WSSV-positive. Most (57%; 16/28) of the brooders in group
A produced nauplii in which the WSSV prevalence was high (>50%).When a
pond was stocked with high-prevalence nauplii from 1 of these group A
brooders, an outbreak of white spot syndrome occurred within 3 wk and only
~20% of the initial population survived through to harvest (after 174 d). By
contrast, 2 other ponds stocked with low-prevalence and WSSV-negative
nauplii (derived respectively from 2 brooders in group B), both had much
higher survival rates (70 to 80%) and yielded much larger (~3x by weight)
total harvests. We conclude that testing the nauplii is an effective and
practical screening strategy for commercially cultured P. monodon.
(Department of Zoology, National Taiwan University,
Taipei, Taiwan, ROC, e-mail of G.H. Kou: ghkou@ccms.ntu.edu.tw)