Fish contains mercury which can harm dogs if they eat too much fish meat without knowing about its harmful effects on their health especially on their nervous system; therefore they should not eat any type of fish meat until they are advised by their vet about its toxicity effect on them because if not treated timely then dog’s body will get affected causing damage especially neurological damage like tremors etc. . It also contains heavy metals like cadmium which can cause kidney failure as well as other diseases such as cancer etc. .