September 12, 2017
Fishmeal makers question research findings
IFFO, the international organisation representing member companies in the fishmeal and fish oil industry worldwide, has questioned the result of a published scientific paper indicating there is a potential for fishmeal used in aquaculture feed to be a vector for antibiotic-resistant genes.
According to the research report, which appeared in the American Chemical Society's Environmental Science & Technology journal, antibiotic-resistant bacteria and genes for antibiotic resistance were surprisingly found in the sediment of marine fish farms even when no antibiotics had been applied.
The researchers said that one suspected source of these bacteria and genes was fishmeal, which is made of low-value fish and seafood byproducts.
The study noted that previous research had found that fish food, which generally incorporates fishmeal, can contain antibiotics, adding that no study had yet measured the abundance of antibiotic resistance genes in the fishmeal.
IFFO said in its response posted on its website that the research paper raised several questions including the conduct of sampling of the Peruvian fishmeal, in which the researchers found seven different antibiotic residues.
The Peruvian fishmeal, IFFO said, is normally made entirely from wild-caught Peruvian anchoveta.
"As the sampling was conducted in China and not in Peru, we are seeking clarification of the measures taken to protect samples from contamination", IFFO said.
IFFO also claimed that antibiotic-resistant genes (ARGs) are susceptible to degradation in the environment and that the transfer of genes to other bacteria is a complex process with a number of conditions that must be met for transfer to occur. "It is not clear what risk detectable ARGs represent in the mariculture environment", it said.
IFFO acknowledged the fact that ARGs have been found to be present in apparently isolated locations including permafrost and cave systems. "They may therefore have become somewhat ubiquitous in the environment", it said.
Possibility of ARGs in other marine sediments
It raised the possibility that ARGs may be present in other marine sediments "The inclusion of a sample control in the paper such as other marine sediments not within the vicinity of a mariculture unit would have helped to identify whether fish farms are actually the source of the ARGs".
IFFO also noted that only very limited other feed ingredients were included in the test. Thus, "it is possible that the presence of nutrients in the sediment (from either fishmeal or other feed ingredients) are encouraging the growth of sediment bacteria which may contain ARGs that do not originate from fishmeal".
Moreover, IFFO observed that fish farms in China "are often notable for their proximity to human populations, and it may well be that any selection pressure on bacterial communities arising from antibiotic use is a result of other sources, such as sewage effluent".