Ongrowing of Octopus vulgaris Cuvier, 1797 in floating cages fed with bogue Boops boops (L., 1758) from fish farm discards

Abstract

The first two experiences of ongrowing the octopus Octopus vulgaris Cuvier, 1797, fed solely on fish of low commercial value, such as discarded bogue Boops boops (L., 1758) accidentally reared in seabream Sparus aurata L., 1758 culture cages, were carried out in the Canary Islands. The present study was made in a floating cage of galvanized mesh, divided vertically into two semi-cages. In a first experiment, individuals of two different initial average sizes were compared: 1.5 kg and 2.3 kg, both stocked at a density of 11 kg/m3. They were reared for 57 days, obtaining octopus of 2.643 kg from the 1.5 kg group, and of 3.812 kg from, the 2.3 kg group. The survival rate was 91 % for the initially smaller group, and 82 % for the larger group. Density of individuals was increased in a second experience, in which the initial sizes were smaller, 1.0 kg and 0.8 kg, in each semi-cage. This second experience was carried out for 81 days, and the final weight of the octopus was 3.111 kg for the 1 kg group and 3.052 kg for the 0.8 kg group, with a survival rate of 44 % for the former and 50 % for the latter. The use of bogue as a single feed was found to be enough to sustain good growth in octopus cage rearing. Best results in terms of specific growth rate and average daily growth were obtained in the lowest size group, 0.8 kg of initial weight, with a SGR of 1.65 %, whereas the smallest rates of growth (SGR of 0.86 %) were in octopus of 2.337 kg of initial weight.