Avaliação e caracterização do mexilhão-dourado incrustado em diferentes telas de tanques-rede

Abstract

Two essays were performed in order to evaluate and characterize the golden mussel incrusted in two types of nets cages (PVC and Bezinal) in an area of tilapia aquaculture in the reservoir of the Itaipu Binacional hydroelectric power plant. In the first essay the characterization and bioaccumulation of gold-mussel metals fouling in two types of net cage was performed. The nets were removed and the evaluation of the average mass, total and dimensions (length, height and width) of the fouling molluscs was evaluated. Later, the ordering of the average lengths was executed, and the quantification of cadmium, lead, aluminum, zinc and chromium of mussels evaluated. The mussels that adhered to the Bezinal net had higher average mass, length, height and width. However, the PVC net provided a greater total mass of mussels encrusted. Subjects with a length between 10 and 20 mm had a higher incidence in the PVC net, and in lengths between 22 and 26mm had a greater frequency of mussels in the Bezinal screen net. The mussels fouling adhered to the Bezinal net had a higher bioaccumulation of Al, Zn and Cr contents when compared to those adhered to the PVC net. In the second experiment, goldfish molluscs in PVC and Bezinal nets were evaluated for first and second use of net-tanks and for the use of oil coating of Nile tilapia. The nets were extracted for the estimation and evaluation of the total mass of substrates, individual average mass, total amount and dimensions of the molluscs. Regarding usage time, PVC nets had the highest values of total mass of substrates, masses and sizes of molluscs. The nets on second use resulted in the highest values of size dimension and average mass of mussels, the largest total mass of molluscs being observed only in the PVC net, and the lowest mass of substrates in the Bezinal net. Regarding the use of oil of Nile tilapia, the largest total mass of mussels and substrates adhered to the PVC net. The oil-bathed nets had lower mean values in the size of the mussels, however, no significant differences were observed for the masses of the molluscs. The use of Bezinal coated wire is more efficient than PVC as an antifouling material. The second-use nets tend to increase the bio-fouling mass. The use of tilapia oil in net tank cages meshes is not efficient as an alternative control for the golden mussel.