The Mississippi State University, Coastal Research and Extension Center has begun investigating the use of natural foods by freshwater prawns, Macrobrachium rosenbergii. Artificial as well as natural substrate, such as rooted aquatic grasses (i.e., dwarf spikerush,Eleocharis parvula), support the growth of attached algae and associated invertebrate organisms that, along with the invertebrate component of the benthic assemblage, serve as a natural food source for prawns. Prawns that seek refuge in either natural or artificial substrate, therefore, have an added benefit of a ready supply of supplemental natural foods, which may contribute to increased yields. The objectives of a previous investigation were to characterize the assemblages of natural foods available to prawns on natural and artificial substrates and to determine if prawns feed on these organisms. Current objectives include quantifying the natural foods available in ponds and assessing their consumption by prawns.
In 2000, natural foods were collected from single ponds in each of four culture treatments associated with a commercial food study, including: a) a bare mud control pond (unstocked); b) a vegetated mud control pond (unstocked); c) a bare mud prawn pond; and d) a vegetated mud prawn pond. Replicate benthic samples (3, 10 cm diameter by 10 cm deep cores) were collected from each pond at three-week intervals for a total of 7 samples over the course of trials.
Based on data previously collected in 1999, several major groups of natural foods were available in ponds, with chironomid midge larvae and oligochaete worms being the most abundant. Consumption of these natural foods was, however, difficult to verify due to the maceration process of freshwater prawns. In most gut samples analyzed, only chironomid head capsules remained identifiable. The current study focused on the characterization and evaluation of the assemblages of natural foods found in bare mud verses vegetated mud samples. The consumption of natural foods by freshwater prawns was indirectly assessed by comparing natural food assemblages found in ponds stocked with and without freshwater prawns.
PUBLICATIONS AND PRESENTATIONS:
Walters, S. C., R. D. Long, M. W. LaSalle, and B. C. Posadas. 2001. Assessment of Natural Foods Available to and Utilized by Pond-cultured Freshwater Prawn Macrobrachium rosenbergii. Page 676 in Books of Abstracts, Aquaculture 2001, World Aquaculture Society, Baton Rouge, Louisiana.