February 15-18, 2009 Washington State Convention Center Seattle ...

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ROUTINE METABOLIC RATE AND LIMITING OXYGEN CONCENTRATION OF
FRESHWATER PRAWN Macrobrachium rosenbergii LARVAE
Brian D. Ott* and Eugene L. Torrans.
USDA ARS Catfish Genetics Research Unit
Thad Cochran National Warmwater Aquaculture Center
P.O. Box 38
Stoneville, MS 38776 USA
brian.ott@ars.usda.gov
Malaysian prawns, Macrobrachium rosenbergii, are hatched and raised indoors in small tanks. Prawns may be raised and
shipped at high densities which could result in low dissolved oxygen (DO) conditions. Because DO may play an important role
in prawn development and survival, we measured routine metabolic rate (RMR) and limiting oxygen concentration (P crit ; the
presumed hypometabolic transition zone) of prawns at four different ages.
Measurements were taken in a closed respirometer consisting of a 300mL BOD bottle fitted with a Hach BOD overflow funnel.
Oxygen consumption ( V & o 2 ) and temperature were measured using a Hach HQ10 luminescent DO meter equipped with a spin
bar on the tip of the probe. Prawn larvae were collected either from hatching or rearing troughs at Lauren Farms, Inc., Leland,
MS. V & o 2 was measured initially after they hatched (0 days post hatch [dph]), at 15 dph and 29 dph, and immediately after the
prawns transformed into post-larvae (31 dph). For each measurement, a prawn sample was collected in a dip net, patted dry and
weighed (1.0 – 1.2g, n=6,000-120), and placed in a respirometer where DO and temperature were measured every minute for
30-100 minutes at an average water temperature of 26.0°C. The P crit was determined as the DO concentration at which prawn
V & o 2 decreased from a linear rate.
Individual prawn V & o 2 was lowest at 0 dph (0.00023 ± 0.00003 mg O 2 n -1 h -1 ) and was 11-, 30-, and 49-fold higher than intial
rates at 15 dph, 29 dph, and 31 dph, respectively. Mass-specific V & o 2 remained unchanged over the four sampling periods and
ranged from 1216 ± 144 mg O 2 kg -1 h -1 on 0 dph to 1300 ± 49 mg O 2 kg -1 h -1 on 31 dph. Limiting O 2 concentration was lowest
at 0 dph (53 ± 1% saturation), peaked at 29 dph (74 ± 1%), and decreased once they became post-larvae (69 ± 1%). Oxygen
consumption and limiting O 2 concentration are factors to consider when raising and shipping prawns and become more critical
issues as they age and grow.