Aquaculture Europe 2023

September 18 - 21, 2023


Add To Calendar 20/09/2023 15:15:0020/09/2023 15:30:00Europe/ViennaAquaculture Europe 2023INFORMING AQUACULTURE MANAGEMENT USING VIBRIO spp. ABUNDANCE AS AN ADDITIONAL INDICATOR OF WATER QUALITYStolz 2The European Aquaculture Societywebmaster@aquaeas.orgfalseDD/MM/YYYYaaVZHLXMfzTRLzDrHmAi181982


M. Purgar*1, A. Gavrilovic2, D. Kapetanovic1, J. Klanjšcek1, J. Jug-Dujakovic3, A. Kolda1, J. Žunic1, S. Kazazic1, I. Vardic Smrzlic1, D. Vukic Lušic4, K. Pikelj5, E. Listeš6, M. El-Matbouli7,8, A. Lillehaug9, S. Loncarevic9, D. Kneževic10, B. Hengl10, S. Gecek1, T. Klanjscek1


1Ruder Boškovic Institute, Croatia

2University of Zagreb Faculty of Agriculture, Croatia

3Sustainable Aquaculture Systems, Inc., USA

4University of Rijeka. Faculty of Medicine, Croatia

5Faculty of Science, University of Zagreb, Croatia

6Croatian Veterinary Institute, Croatia

7University of Veterinary Medicine, Austria

8School of Biotechnology, Badr University in Cairo, Egypt

9Norwegian Veterinary Institute, Norway

10Croatian Agency for Agriculture and Food, Croatia





Bacterial presence in the water column can adversely impact fish health and, therefore, aquaculture production. For example, Vibrio spp. are ubiquitous heterotrophic bacteria found in aquatic and marine environments that can cause vibriosis, a potentially fatal disease in humans and aquatic animals (Baker-Austin et al, 2018). Pathogenic Vibrio spp. have already been causing mass fish die-offs, thus adversely affecting both farming and the environment; their impact is projected to increase due to climate change and other anthropogenic factors (Sampaio et al, 2022).

Water quality has generally been monitored using bacterial indicators such as heterotrophic plate counts, total coliforms, and fecal coliforms (Some et al, 2021). However, bacterial indicators such as Vibrio spp. have been ignored despite their potential importance in monitoring water quality in coastal areas. Although Vibrio spp. are regulated for food products (ISO 21872-1:2017), uniform guidelines and official regulations for monitoring their environmental presence in management strategies are still lacking.

Materials and methods

In this study, we examine the applicability of Vibrio spp. abundance as an additional indicator of water quality for informing science-based coastal management. To achieve this, we analyzed a three-year open dataset from Mali Ston Bay that included standard environmental and bacterial indicators, as well as Vibrio spp. abundance (Jug-Dujaković et al, 2022).  To determine whether Vibrio spp. abundance provides additional information on water quality, we assessed the seasonal, spatial, and vertical variations of environmental and bacterial indicators such as HPC (heterotrophic plate counts), TC (total coliforms), E. coli, enterococci, and Vibrio spp. abundance, and their interrelationships. Specifically, we examined: (i) the extent of emissions from the fish farm, (ii) the environmental factors that impact Vibrio spp. abundance, and (iii) the variability of Vibrio spp. abundance in relation to other potential pathogens, including E. coli, enterococci, and heterotrophic bacteria overall. Differences between seasons (warm and cold), sites (fish farm and control) and depths (surface, 5m, 10m and bottom) for both environmental and bacterial indicators were investigated by permutational multivariate analysis of variance (PERMANOVA; Anderson, 2001). Relationships between environmental and bacterial indicators were assessed with Pearson’s correlation analysis and RDA (Legendre and Legendre, 2012). Finally, the distributions of pathogenic bacteria (E. coli and enterococci) in the water column was compared to that of Vibrio spp. by using water quality abundance categories (as defined in the Official Gazette of the Republic of Croatia 73/08). Official standards for Vibrio spp. for assessing water quality were not yet available, so we estimated one using a threshold of 100 CFU/ml reported to result in bacterial transmission into organisms after prolonged exposure to Vibrio spp. (Kim and Lee, 2017). We assumed the 100 CFU/ml critical value represents a threshold defining ‘sufficient’ water quality, and extrapolated the other thresholds using classification for enterococci, who share the same critical value for ‘sufficient’ water quality.


Our results show no differences between the fish farm and control site in terms of environmental conditions, organic enrichment, and bacterial abundance. However, the abundance of heterotrophic bacteria, enterococci, and Vibrio spp. was unexpectedly higher during the cold season. E. coli and total coliforms, in line with traditional patterns, were more abundant during the warm season.  Temperature was found to be the best predictor of Vibrio spp. abundance when examining the correlation among explanatory variables in RDA, followed by total phosphorus. This finding reinforces the significance of temperature and the often restrictive nutrients in driving the dynamics of bacterial abundance. According to the thresholds from the Official Gazette 73/08, water quality was generally excellent. The best score was achieved by E. coli, with over 95% of samples collected at each site meeting the criteria for excellent quality. Enterococci showed excellent quality in more than 91% of the samples, while less than 64% of samples tested for Vibrio spp. fell into the excellent category. The notably lower result for Vibrio spp. suggests that either (i) there is a genuine concern regarding the prevalence of potentially pathogenic Vibrio spp., or (ii) the thresholds adopted from the enterococci regulations may not accurately reflect the risk of disease.


This research was funded by the Croatian Science Foundation (HRZZ) project AQUAHEALTH no. IP-2014-09-3494 to D.K. and and DOK-2021-02-6688 to T.K. for M.P.


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Sampaio et al, 2022. Diversity, 14, 97.

Some et al, 2021. Energy Nexus, 1, 100008.

ISO 21872-1:2017

Jug-Dujaković et al, 2022. PANGAEA

Anderson, 2001. Austral Ecol, 26, 32-46.

Legendre and Legendre, 2012. Elsavier.

Kim and Lee, 2017. Front Mar Sci, 4, 147.