Experimental culture of the freshwater crab Dilocarcinus pagei: effect of density on the growth

Abstract

This study investigated the effect of culture density on the juvenile development of the freshwater crab Dilocarcinus pagei, analyzing the mortality, size increment and mutilation. Juvenile crabs were cultured for 90 days in three treatments with three replicates: T1 - 2 animals L^-1; T2 - 3 animals L^-1; and T3 - 4 animals L^-1. Mortality was high and increased with density: T1 = 70.0 ± 10.0%, T2 = 73.3 ± 3.2% and T3 = 81.6 ± 2.9%. The size increment (mm) did not differ significantly among the treatments, and the means were 7.86 ± 1.76 (T1), 9.33 ± 1.21 (T2) and 8.56 ± 0.53 (T3). However, the specific growth rate was higher in T2, that had a tendency for more growth, as demonstrated by linear regression (ANCOVA, F =10.04; DF = 2; P<0.001). Crabs cultured in the same period grew to different sizes over the course of the experiment. The mutilation was not density dependent, and the size of the mutilated individuals was significantly smaller than that of the non-mutilated crabs (Z = 2.4565; P = 0.0140). Among crab densities tested, the most suitable density for aquaculture was 3 animals L^-1 due to highest specific growth rate presented, despite the high mortality.