Fish protein is much more easily digestible so its beneficial for sensitive stomachs. This also makes it good for older dogs who have slower rates of digestion.
Fish skins are also low in fat which is great for weight control.
Fish contains Omega-3, this is a natural anti-inflammatory which will benefit dogs suffering with joint pains and helps to maintain joint health.
For those suffering from allergies, fish is great as its hypoallergenic.