G. Marino1*, P. Di Marco1, T. Petochi1, M.G. Finoia1, P. Tomassetti1, S. Porrello1, G. Parisi2, G. Giorgi2, M. Lazzaro3 and B.M. Poli2
1 ISPRA Italian National Institute for Environmental Protection and Research, Rome, Italy
2 DISPAA Dept. Agrifood Production and Environmental Science, University of Florence, Italy
3 Technical consultant of Ittica Golfo di Follonica Company, Piombino, Italy
E-mail: giovanna.marino@isprambiente.it
Introduction
Organic aquaculture is based on the principles of environmental sustainability, product quality and safety, as well as animal welfare (IFOAM, 2010). Current Regulation 710/2009/EC provides some detailed rules on organic production and a further implementation is expected by 2017 (COM(2014) 180 final). There are still several controversial issues on organic production of carnivorous fish species in intensive farming systems, mainly related to feed sources, animal welfare, disease prevention, environmental interactions, which require more knowledge to increase consumer confidence in organic aquaculture and to ensure its future development (FEAP, 2012).
This study aimed to compare growth, welfare and quality traits of European sea bass Dicentrarchus labrax (L.) and gilthead sea bream Sparus aurata (L.) farmed in sea cages according to conventional and organic production method, as well as their interactions with the surrounding environment.
Materials and Methods
Site description and farming management - The study was carried out from September 2011 to December 2012 in a commercial sea cage farm (2 net pens with 12 cages each) located in the Central Tyrrhenian Sea, about 2 nautical miles from the Tuscany coast and with the following environmental features: sand-mud sediment, water depth ranging from 22 to 28 m, dominant sea current direction along a NW/SE axis and mean velocities < 15 cm/s. Conventional and certified-organic juveniles (initial weight of about 11 g) were reared in four circular 3.800 m3 floating sea cages (two for each species), at approx. 15 kg/m3 final stocking density for sea bream and 10 kg/m3 for sea bass. Fish were fed on conventional and certified organic commercial feeds.
Sampling and analyses - Fish sampling was carried out in December 2012 at commercial size. Fish were captured by net confinement, stunned in ice/water slurry and sacrificed with a blow to the head. Fish were evaluated for growth performance and animal welfare through physical and physiological indicators, according to Marino et al. (2007). Product quality was assessed by analyzing morphological, chemical, nutritional and sensory parameters of fresh fish and fillets according to Poli et al. (2001).
Environmental impacts resulting from sea cage farming were evaluated by analyzing nutrient content in water and sediment samples according to Porrello et al. (2005) and macrobenthic community according to Tomassetti et al. (2009).
All data sets were statistically analyzed within each species to evaluate the effects of the two farming production methods on animal welfare, product quality and environmental impact.
Results
Growth performance and fish welfare - Organic fish showed better growth performance than conventional ones (365 vs 307 g for sea bream and 267 vs 225 g for sea bass). All fish were found to be in good health conditions. No skin and eyes lesions were observed, fin erosions were negligible and the mean splitting index of all fins in organic and conventional fish was 1.41 vs 1.19 in sea bream and 0.71 vs 0.17 in sea bass (0-3 score index). Fish showed no sign of physiological stress and energy deficit. Altered levels of serum proteins and enzymes were observed both in organic sea bream and sea bass compared to conventional ones.
Quality traits- Morphological and chemical parameters were similar in organic and conventional sea bream, whereas lower perivisceral fat (21 vs 37 %) and lipid content (5.8 vs 7.4%) were observed in organic sea bass. A similar fillet yield was found in organic and conventional fish (45-46%). Significant differences were found in the muscle fatty acids profile between organic and conventional groups. Lower levels of n-3 PUFA (16/17 vs 21 %) and n-3/n-6 FA ratio (0.7/0.8 vs 1.4/1.5) were found in organic specimens than in conventionally-farmed fish due to their higher content of linoleic acid (20/21 vs 14/13 %), reflecting feed composition. Fish sensory characteristics and shelf life were similar in both organic and conventional groups. Fish of both species were classified as extra quality until 5th day and as good quality (class A) until 8th day, with a 12-day and 13-day shelf life for sea bream and sea bass, respectively.
Environmental aspects -A slight increase in carbon and phosphorus concentrations in the sediment, as well as some changes in macrobenthic community were detected in the stations located just beneath the conventional and organic sea cages. These environmental effects were no longer evident at distance of 25 m from the two sub-areas.
Discussion and conclusions
Comparative literature data on organic and conventional production systems are still scarce (Mente et al., 2012) and this study has addressed some relevant issues of sea bass and sea bream organic production through an integrated and comparative approach. Results showed a better growth performance of organic farmed fish which could be explained in terms of diet and/or difference in organic vs conventional juveniles quality. The slightly higher incidence of fin splitting observed in organic farmed sea bream and sea bass could be related to their bigger size at the end of the farming cycle, and/or possible different feeding behaviour. Differences in blood chemistry parameters between organic and conventionally farmed fish could be interpreted as a sign of some difficulties in the digestion of vegetable ingredients contained in the organic diet. Similar morphological, chemical and sensory traits were found in organic and conventionally farmed fish, with the exclusion of the lower n-3/n-6 FA ratio in flesh of organic fish, reflecting the similar difference in the diets. Both organic and conventional sea cage farming have a minor impact on surrounding water and sediment, but direct comparisons between the two methods were not possible due to the different biotopes found in the two sub-areas considered. We concluded on the good performance of organic practices for sea bass and sea bream production in sea cages, ensuring good fish welfare and having similar environmental effects to those found for conventional sea cages. The quality of organic feeds remains an important issue to be addressed, to ensure the nutritional quality of organic fish.
Acknowledgments
The study was carried out under the contract between ISPRA and the "Ittica Golfo di Follonica" Company. We thank A. Longobardi, C. Greco, V. Donadelli, A. Priori, A. Bonelli, I. Mercatali, P. Gennaro, E. Persia and D. Vani for technical assistance during sampling and laboratory analyses.
References
FEAP. 2012. Annual report. http://www.feap.info/Default.asp?SHORTCUT=617.
IFOAM EU Group, 2010. www.ifoam-eu.org/positions/publications/aquaculture
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