Influence of spatial distribution and shelter area upon survival and growth of Cherax quadricarinatus (Parastacidae) juveniles, and its application to intensive culture

Cherax quadricarinatus is an interesting species for aquaculture and is more tolerant to high densities than other species of commercially important crustaceans, making it suitable for intensive culture. The purpose of this study is to determine the most adequate spatial arrangement and area of onion bag mesh, commonly used as shelter in juvenile culture, to decrease mortality and improve growth under high-density conditions. Two experiments were conducted to evaluate the optimum onion bag mesh spatial distribution (parallel pieces of mesh arranged in a vertical and horizontal position, and mesh with a random arrangement), and area (0.612 m2, 1.224 m2 and 1.836 m2) under high-juvenile density conditions (41.7 one-gram juveniles per m2). The weight and number of juveniles were recorded, and mortality and biomass were calculated at day 60. In the second experiment, the number of missing chelae and juveniles with all their walking legs were counted to estimate agonistic interactions. Mortality was lower in the treatment consisting in randomly arranged onion bag mesh and that with the smallest area. A mesh surface of 2.55 m2 per m2 of ground would be sufficient as shelter for juveniles stocked at high densities. Biomass and antagonistic interactions were similar in all cases. This study showed that a random arrangement of onion bag mesh is the most adequate and economic shelter for C. quadricarinatus juveniles, and that the use of high mesh areas could decrease survival in culture.