Microbiology of striped bass grown in three aquaculture systems

ISSN： 0740-0020

Source： Food Microbiology, Vol.14, Iss.3, 1997-06, pp. : 255-264

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Abstract

The effects of three aquaculture systems (earthen ponds, flow-through tanks and recirculating tanks) on the numbers and types of micro-organisms isolated from the skin (S), gills (G), intestinal contents (I) and cultivation water (W) of striped bass ( Morone saxatilis ) and hybrid striped bass ( Morone chrysops x Morone saxatilus ) were determined. Plates counts were performed aerobically and anaerobically at 35, 22 and 7#°C; randomly-selected isolates ( n =1742) from the aerobic plate counts were identified using MIDI and BIOLOG systems. Enrichments and selective plating were used to detect foodborne pathogens. A mixed model analysis of variance was used to determine significant differences ( P <0.05) among plate counts; data for the S, G, I and W were analysed separately. Aquaculture system had no significant effect on any of the plate counts for the S, G, I or W. Aerobic plate counts were significantly higher than anaerobic counts at the same incubation temperature for the S, G and W, but for the I, aerobic and anaerobic counts were not significantly different. Under the same incubation atmosphere, counts at 35 and 22#°C were not significantly different from each other, but counts at both temperatures were significantly higher than counts at 7#°C. The types of bacteria randomly isolated were similar for all systems, but their prevalence varied; incubation temperature affected the genera isolated. The predominant microbial groups randomly isolated from the fish samples from all systems and tissues were Aeromonas (19%), Flavobacterium/Cytophaga/Chryseobacterium (16%), Bacillus (7%), Moraxellaceae (6%), Pseudomonas (6%), corneforms (5%), Plesiomonas (5%) and Micrococcaceae (4%). No Salmonella or Yersinia enterocolitica were isolated, and Listeria monocytogenes , Shigella dysenteriae , and Yersinia pseudotuberculosis were each isolated only from ponds on only one sampling day. Staphylococcus aureus and Vibrio spp. occurred in all systems in low numbers.