Effect of density on the growth of striped mullet (Mugil platanus) reared in mono and policulture with common carp (Cyprinus carpio), in Vale do Ribeira region

Abstract

This work was carried out to test four different stocking densities of striped mulIet reared in mono and polyculture with common carp. The treatment were, in monoculture - Treat.A = 1 fish/6 m²= 25 striped mulIet/pound; Treat.B = 1 fish/3 m² = 50 striped mulIet/pound; in poly-culture - Treat.C = 1 fish/1.5 m² = 25 striped mulIet and 75 common carp/pound; Treat.D = 1 fish/0.75 m² = 50 striped mulIet and 150 common carp/pond. Each treatment was repeated twice. This study was developed in the period between February and June/1990 in 8 ponds of 150 m² each, belonging to Cacau-açu Farm, in Pariquera-açu City (24°49'S; 47°50'W). All the ponds received the same quantity of fertilizer. During the experimental period, the water was sampled for posterior limnological analyses. The results of growth and weight gain obtained in each treatment were, respectively: Treat.A - striped mullet = 88.02 mm and 53.96 g; Treat.B - striped mulIet=86.73 mm and 37.57 g; Treat.C - striped mullet = 69.93 mm and 34.68 g and common carp = 143.21 mm and 90.77 g; Treat.D - striped mullet = 67.03 mm and 30.92 g and common carp = 86.60 mm and 35.84 g. The comparative study of growth and weight gain data indicated a small difference between the mullets of treatments A and B, and C and D, but the striped mullet reared in monoculture and in lower density had greater growth and weight gain. The growth of the carps was ever greater than that of striped mullets. There were significant difference (P>0.01) among the treatments, to total biomass, what don't occurred with mullet biomass and survival. From these results it was estimated the fish production (mullets and carps) in the ponds (kg/ha.year): Treat.A = 129.85 (mullets); Treat.B = 174.78 (mullets); Treat.C = 913.86 [110.08 (mullets) + 803.78 (carps)]; Treat.D = 760.42 [137.77 (mullets) + 622.65 (carps)].