Insights into organic farming of European sea bass Dicentrarchus labrax and gilthead sea bream Sparus aurata through the assessment of environmental impact, growth performance, fish welfare and product quality

Abstract

The organic farming of sea bass and sea bream was investigated in a commercial farm by assessing environmental impact, growth performance, fish welfare and product quality in a multidisciplinary approach. Organic and conventional juveniles were reared in four circular 3.800m3 floating sea cages at a maximum final stocking density of 15kg/m3 and fed on organic or conventional commercial feeds. Conventional farming was started simultaneously and monitored as the reference condition. Environmental and biological samplings were performed after 16months at the first fish harvesting. No environmental impact was observed in the organic farming area, whereas a significant increase in total phosphorus concentration in the sediment and some changes in the structure and species composition of benthic assemblages were detected just beneath the conventional sea cages with no impact 25m from the cages. Organic fish showed a better growth performance consistent with the lower feed conversion ratio and higher metabolic status, as evidenced from the protein and energy profiles, compared with conventional fish. No dietary influence on stress and immune response was observed. A higher incidence of fin splitting occurred, probably due to nutritional factors and/or to the larger size of organic fish.Similar good morphological, physical and sensory traits between organic and conventional fish were observed, as denoted by the high fillet yield, low flesh lipid content, long freshness and shelf life both in sea bream and in sea bass. Conversely, the fillet fatty acid composition was different, being poorer in n-3 PUFA and richer in linoleic acid (C18:2 n-6) in organic versus conventional fish, mirroring the fatty acid profile of the diet.The organic farming of sea bass and sea bream exhibited an overall good performance. Husbandry and feeding practices did not produce any evident environmental impact although long-period investigations covering several full production cycles are needed. Organic fish grew well, displayed an overall state of well-being and had good quality features despite a lower EPA and DHA content. Improvement of organic feed formulation and quality of feed ingredients emerge as important issues to be addressed to optimize the nutritional quality of organic sea bass and sea bream.