EFFECT OF STOCKING DENSITIES ON TRACE-METAL CONCENTRATION IN 3 TISSUES OF THE BROWN SHRIMP PENAEUS-CALIFORNIENSIS

The influence of stocking density in tidal ponds on the concentration of trace metals and macroelements in three shrimp tissues was evaluate d. Brown shrimps Penaeus californiensis were stocked in three 1 ha ear then-bottom tidal ponds at densities of 4, 8, and 10 shrimps per m(2). After 4 months, the animals were collected, weighed, and dissected fo r metal determination (copper, cadmium, lead, zinc, iron, sodium, pota ssium, magnesium, and calcium) in the hepatopancreas, muscle, and abdo minal cuticle. Although no significant differences were obtained for p hysicochemical variables in the water, an increase of nitrates and ort hophosphates was observed in the pond with the highest density occurri ng at the end of the experiment. The average body weight of shrimp dec reased as the stocking densities increased. The concentrations of Cu a nd Cd in the hepatopancreas were higher with increasing stocking densi ty. Pb in the hepatopancreas was significantly higher in the animals s tocked at the intermediate density. Several correlations between trace metals and macroelements were obtained. Different stocking densities could, over the long term, affect the water chemical speciation and th e availability of the elements for the shrimp. (C) 1997 Elsevier Scien ce B.V.