My mother in law wants me to feed my boy this. He's 7 months old. Is this safe and what are the benefits? How can we cook this?

Is this silver fish? It can be used to boil in soup to give it more flavourful (either u grind in powdery form or just put some in). Smaller fish like anchovies/silver fish have more nutritious value than bigger fish. Read http://healthyeating.sfgate.com/health-benefits-anchovies-2748.html Dont put alot as your baby might get used to flavourful taste than the natural taste.