As long as the contaminant content of fish meets the relevant standards, there is no problem for us to eat it. Of course, if you want to consume as little pollutants as possible, it would be a better choice to choose fish that are raised in appropriate ways, herbivorous or omnivorous, eat more fish and less fish offal, and diversify your diet.
An important source of pollutants in fish is water. Natural water bodies receive and contain various pollutants, and the risk of fish living in them being exposed to pollutants is not low at all. There are also studies showing that some pollutants entering water bodies are preferentially accumulated by aquatic organisms.
The accumulation of pollutants in fish is largely related to the growth rate of fish. Artificially farmed commercial fish are generally selected species with faster growth rates, while wild fish generally grow slower than farmed fish. For example, the weight gain of common farmed crucian carp species is 40% faster than that of wild species. %about. Contaminants accumulated by farmed fish from the water are "diluted" by faster accumulation in muscle tissue. A study in South Korea also showed that the heavy metal content in the muscle of wild fish on the coast is higher than that of farmed fish. In a study on mercury accumulation in Qiandao Lake fish, the mercury concentration in cage-cultured carnivorous fish was also lower than that in wild carnivorous fish.
"Big fish eat small fish, small fish eat shrimps", this is an image description of the food chain in the water. The big fish eat not only the small fish, but also swallow the pollutants in the small fish. Those pollutants that are not easily excreted will continue to accumulate in the big fish. This is "biomagnification". effect. Many studies have shown that in the wild environment, the pollutants eaten by the top carnivorous fish have undergone multiple "biomagnifications" and the concentration is much higher than that in the water body and other fish. Relatively speaking, this biomagnification effect will be much smaller for farmed fish fed with feed.
But this does not mean that farmed fish are completely safe.
In my country, the water quality of some breeding water bodies is not optimistic. The antibiotic problem caused by the use of fish medicine requires stricter supervision and control, and the accumulation of pollutants caused by bait also needs attention. Food crops contain high levels of heavy metals such as cadmium, which are likely to be enriched by fish through fish feed. A study comparing wild large yellow croaker and farmed large yellow croaker found that wild populations have higher levels of heavy metal mercury, while farmed species have higher levels of cadmium. In a study in Hunan, the lead and cadmium content of wild grass carp in Dongting Lake was lower than that of farmed grass carp in Changsha City. This is also believed to be due to the higher concentration of heavy metals in rice feed in Hunan Province.
From this point of view, just looking at whether it is wild or farmed cannot answer the question of how much pollutants are consumed, but compared to wild fish, farmed fish are more "controllable" and relatively less I can feel more at ease.