Microbiological controls in polyculture farming: A pilot case study in the Castellammare Gulf (Sicily)

Caruso G*, Caruso R and Sarà G

Background: Integrated multi-trophic aquaculture (IMTA) experiences, based on the co-cultivation of two or more organisms, have proliferated in recent years; nevertheless, studies regarding the microbiological implications of these farming systems are not available yet. 

The context and purpose of the study: The microbiological conditions of shellfish and surrounding rearing environment were investigated during a pilot polyculture system (fish and shellfish farming) performed in the Castellammare Gulf (Sicily). The quantitative distribution of faecal coliforms and enterococci as faecal pollution indicators, together with that of environmental and potentially pathogenic halophilic vibrios, was determined in two different seasons (spring and autumn). Samplings of surface waters and bivalves (oysters, Cassostrea gigas and Ostrea edulis; mussel, Mytilus galloprovincialis, and clam, Tapes philippinarum) were performed at stations where integrated polyculture was performed (Impact sites) compared to others (Control sites) where farming activities regarded shellfish only. 

Results: Higher numbers of faecal pollution indicators were detected in waters at the Impact than at Control ones, generally in spring, although polyculture seemed to have only a low impact over the area. Shellfish products were characterized by vibrios concentrations higher than in waters, due to their filter-feeding activity. They ranged in the order of- 102-103 CFU/g, with higher abundances in spring in the specimens reared at the Impact sites; conversely, in shellfish farmed at the Control sites, no significant quantitative variations were found between the two samplings. The qualitative study of vibrios isolated from both shellfish and environment showed the ubiquitous distribution of V. alginolyticus, and the predominance of V. vulnificus at the Impact sites in both shellfish and waters, representing the 40% and 27% of the total isolates, respectively. 

Main findings: Overall, the low levels of microbial contamination detected in the area showed that polyculture did not result in a heavy impact on the surrounding environment. 

Conclusions: The results obtained in the polyculture experiment performed in Castellammare Gulf suggest the use of this system as a sustainable farming strategy for productive purposes. 

Brief summary: During a pilot experiment of integrated aquaculture, the microbiological quality of the shellfish products was assessed, proving that this productive practice did not give negative results on the concentrations of total heterotrophic bacteria, faecal pollution indicators and potentially pathogenic vibrios. 

Any potential implications: Polyculture is suggested as an ecofriendly farming system, that allows the production of shellfish safe for consumers. 

Keywords:

Published on: May 11, 2020 Pages: 14-28

Full Text PDF Full Text HTML DOI: 10.17352/jcmbt.000039
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