Effective use of plastic
sheet as substrate in enhancing tropical oyster (Crassostrea iredalei
Faustino) larvae settlement in the hatchery
M.N.
Devakie, A.B. Ali-2002
Aquaculture, 212(1-4): 277-287
Abstract:
Various methods were employed to exploit plastic
sheet as substrate for enhancing tropical oyster (Crassostrea iredalei)
larval settlement in the hatchery. Plastic texture (rough and smooth
surfaces) and condition (with and without biofilm) showed a significant
difference (P<0.05) on the larval setting rate. The highest
setting rate was achieved for rough plastic without biofilm (37.6±2.2%)
followed by rough plastic with biofilm (27.1±1.8%), smooth plastic with
biofilm (22.0±2.1%) and the least recorded was on the control or smooth
plastic without biofilm (11.0±1.2%), all of which differed significantly (P<0.05).
Plastic substrate also appeared attractive to setting larvae by presoaking
it in tissue extracts of several bivalve species. Plastic sheets presoaked
in tissue extracts of C. iredalei and Crassostrea belcheri
promoted better setting rates (28.3±3.9% and 26.1±5.5%, respectively) as
compared to those soaked in tissue extracts from other bivalve species such
as the green mussel, Perna viridis (15.7±1.4%) and the rock oyster, Saccostrea
cucullata (12.9±3.6%). The setting rate on the control was also low
(15.3±2.7%) and was not significantly different (P>0.05) from
plastic with tissue extracts of the green mussel and the rock oyster.
Exhalent water (used as media) from the above mentioned bivalve species were
also found to increase oyster larval settlement on plastic substrate as
compared to the control (without exhalent water). Higher setting rate was
obtained for plastic with exhalent water from S. cucullata (48.9±3.5%)
followed by C. belcheri (32.0±2.3%), P. viridis (30.4±4.3%)
and C. iredalei (27.0±1.7%) which did not vary significantly (P>0.05),
while lower setting rate was recorded for the control (18.9±5.9%).
(Fisheries Research Institute, Batu Maung, 11960
Penang, Malaysia, Tel.: +60-4626-3925; fax: +60-4626-2210, e-mail: devakie@yahoo.com)