The samples were collected on fishing vessels during commercial pelagic fishing, and a total of 628 fish were analysed. In addition, 179 samples were taken from the surface of equipment that comes into contact with the fish, and 59 water samples were analysed.
Fish from Norwegian waters are rarely the cause of foodborne disease, which is among other things confirmed by the low prevalence of the pathogenic bacteria Listeria monocytogenes in fish (1.3%).
High levels of intestinal bacteria found in storage water
Enterococci and E. coli do not occur naturally in fish or in the marine environment. Such bacteria are known as indicator organisms for faecal contamination and come from the intestines of warm-blooded animals. Findings of intestinal bacteria can reveal contamination from sewers, run-off from land, birds or inadequate personal hygiene among the people who process the fish.
A total of 40% of all the sample collections included samples with elevated levels of intestinal bacteria in the water from the storage tanks, of which enterococci and E. coli were identified in 11 and four cases, respectively. The water on board the fishing vessels consists of refrigerated sea water, and the area where the tanks are filled is crucial to ensuring safe and good storage conditions for the catch.
In one case, large amounts of E. coli were also found in ten out of 20 fish, with individual findings of 240 E. coli per gram. In this case, the storage water also had high E. coli values. An unfortunate choice of location for filling the storage tanks was probably the reason the fish were contaminated with the intestinal bacteria.
Fish can be given longer shelf lives
NIFES has also analysed the total number of bacteria in a total of 390 fish, and the average count was 1 million bacteria per gram of fish, which is high for fresh raw material. A lower bacterial count could have contributed to an improved shelf life for these fish products.
‘A focus on hygiene from capture to the consumer is important because bacteria that attach early can follow the product throughout the whole production process and affect the safety and quality of the end product,’ says Cecilie Smith Svanevik, scientist at NIFES.
An evaluation form developed as a possible tool
The data set of samples has been collected over the course of ten years and includes 12 sample collections from fish landing facilities.
In order to assess the samples together, NIFES scientists have developed an internal evaluation form. The form defines three categories with ‘good’, ‘acceptable’ and ‘not acceptable’ values for fish, surfaces and production water. An overall evaluation showed that 75% of the total 41 sample collections had room for improvement with respect to the microbiology of the fish or the production environment.
‘The form was primarily developed so that we could evaluate the whole data set collectively, but we hope that this tool can also be useful to the industry,’ says Svanevik.