Contribution of the natural biota associated with
substrates to the nutritional requirements of the post-larval shrimp, Penaeus
esculentus (Haswell), in high-density rearing systems
M.A. Burford, M.J.
Sellars, S.J. Arnold, S.J. Keys, P.J. Crocos, N.P. Preston-2004
Aquaculture Research, 35(5): 508-515
Abstract:
The
contribution of epiphytes associated with physical substrates to the
nutritional requirements of post-larval shrimp, Penaeus esculentus
Haswell, was determined in high-density rearing systems (3000, 6000 and 11 000 m-3).
Stable isotope signatures of epiphytes on polyethylene mesh substrate,
AquaMatsTM and tank walls were compared with shrimp signatures. Two methods were used:
the determination of carbon and nitrogen natural abundance ratios; and 15N-nitrogen
enrichment ratios after the addition of 15N-ammonium to tanks.
Using the natural abundance technique and a simple mixing model, epiphytes
were found to contribute substantially to the carbon requirements of
post-larval shrimp (39-53%). This was despite the addition of formulated
feed at satiation levels. There was no indication of a reduced contribution
of carbon from epiphytes to shrimp nutrition at higher shrimp densities. The
lack of a difference in the 15N/14N ratios of the two
food sources meant that mixing models could not be used to calculate the
contribution of nitrogen from epiphytes vs. artificial feed to shrimp
nutrition. Using the 15N-nitrogenenrichment method, the amount of
nitrogen contributed by epiphytes to shrimp nutrition over 24 h could
be determined. This method showed that nitrogen from epiphytes was
assimilated by shrimp. 15N-enrichment methods provided a more
accurate alternative to natural abundance techniques, particularly when the
stable isotope signals of the food sources are similar. This experiment has
shown the benefits in providing substrates for P.esculentus in
high-density rearing systems to provide an additional food source for
shrimp.
(Centre
for Riverine Landscapes, Griffith University, Nathan, Queensland, 4111,
Australia. E-mail: m.burford@griffith.edu.au)