Effects of selective harvest of amazon river prawn, Macrobrachium amazonicum on pond
water, sediment and effluent
KEPPELER¹, E.C. & VALENTI², W.C.
1 University Federal of Acre, CCBN campus Floresta, Cruzeiro do Sul, Acre, Brasil.
2 São Paulo State University, Aquaculture Center (CAUNESP), Dept. de Biologia Aplicada à Agropecuária, FCAV, UNESP, 14884-900, Jaboticabal, São Paulo, Brazil.
ABSTRACT: In freshwater prawn grow-out phase, the harvest can be total, selective or combined. The harvest can be considered as a periodic antropic factor that greatly modifies the pond ecosystem. Thus, the effect of harvest type (with seining or not) on pond water variables, sediment and effluents was investigated. Six 0.01-ha ponds were stocked with 20 M. amazonicum juveniles per m2. Three ponds were seined fortnightly from 12th week on (selective harvest), while the other three were non-seined. Certain variables of water and effluent were monitored weekly, that is, dissolved oxygen, biochemical oxygen demand, pH, total alkalinity, electrical conductivity, nitrate-N, nitrite-N, ammonia-N, soluble phosphate, total phosphate, chlorophyll a, chlorophyll b, chlorophyll c, pheophytin, total dissolved solids and turbidity. The concentrations of organic carbon, total nitrogen and total phosphorus in sediment were also determined. Variables were compared between the treatments and day periods, for Student Test t . Temporal variation presented similar pattern in both treatments. Selective harvest did not alter pond water characteristics or the sediment. However, daily differences were seen for dissolved oxygen, pH, soluble phosphate and total dissolved solids in seined and non-seined ponds due to community metabolism. Data indicated that selective harvest does not impact pond water and sediments as well as effluents.
Key-words: pond water quality and sediment, effluents, selective harvest, Macrobrachium amazonicum.