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Evaluation of environmental nitrogen and phosphorus contributions as a result of intensive ongrowing of common octopus (Octopus vulgaris)

Mazon, M.J., Piedecausa, M.A., Hernandez, M.D., Garcia Garcia, B.
Aquaculture 2007 v.266 no.1-4 pp. 226-235
Octopus vulgaris, mariculture, digestibility, feces, nitrogen, phosphorus, Carcinus
Octopus vulgaris ongrowing has recently begun to develop in Spanish coastal waters as a result of the need to diversify aquaculture products in terms of their biological and market potential. The aim of this work was to evaluate the possible environmental impact arising from the intensive ongrowing of common octopus in sea cages by estimating the waste generated during one growth cycle as a useful tool for improving the management of future installations and in an attempt to limit such an impact. To do this, we used a nutritional estimate based on the apparent digestibility coefficients of two fresh diets with a low market value (Boops boops and Carcinus mediterraneus). We obtained high digestibility coefficients with mean values of 98.2% for protein, 95.7% for lipids, 95.6% for phosphorus and 92.5% for dry matter. Significant differences were found for the digestibility of protein, lipids and phosphorus as a function of weight, whereas the differences due to the type of food being used were only significant for lipids. To evaluate the influence of these two factors on the digestibility coefficients, a multiple regression analysis was performed; this provided a poor fit and was only significant in the case of lipid digestion. In an installation producing 1000 kg, the main environmental impact would come from the non-edible fraction (50% crab and 23.3% bogue) and particulate wastes, since the first diet would generate 110.6 kg of N and 37.9 kg of P using crab as food, while the corresponding figures for bogue would be 71.7 kg of N and 16.8 kg of P.