What happens when a dog eats fish food?

My dog ped away this morning after suffering from stomach problems for about a week (vomitting, weakness, loss of appetite, etc.). I didn't know what happened to cause such an illness besides the fact that he was 13 years old and nearing his life expectancy. On my drive home I realized that about two weekends ago he consumed about a handful of fish food pellets while exploring my friend's backyard. Would eating fish food cause stomach failure?