Design, development and construction of open sea floating cage device for breeding and farming marine fish in Indian waters

Abstract

The floating cage device described in the present study is the first of its kind in Indian seas and consists of a cylindrical floating cage structure along with suitable netting materials for mariculture of finfishes and shellfishes in open sea. The cage structure was made of high density polyethylene (HDPE) top support, inner and outer rings and a middle catwalk. The inner and outer collar had provisions for connecting outer predator, inner growout and bird nets. Catwalk in the middle served for regular cage management and safety of the workers. There were HDPE vertical and diagonal supports for the cage frame. Ballast was used at the bottom to maintain the shape of the cage. The total weight of the cage frame was 447.7 kg in air and 74.2 kg in water. The floatation force of the cage was 211.2 kg while the effective floatation force was 131.8 kg. The total weight of netting materials including rope was 46.7 kg in air and 5.2 kg in water. A floating net cage device of 6 m inner and 8 m outer collar dia with 6 m net depth and an effective inner volume of 169.7 m3 was designed and successfully tested in open sea, during the present study. The floating sea cage structure and nets were designed and standardised in such a way to suit the current and wave conditions of Indian seas.