Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain as you have taken tuna that is fish and comes under seafood, therefore vomiting after taking it long with stomach ache can be either due to indigestion or can be due to seafood poisoning.. It can be either due to contamination of the fish with bacteria, viruses, paasites, chemical toxins and chemicals etc.. In case if you get the symptoms again like vomiting, loose motions, stomach cramps, fever etc, you should consult a Gastroenterologist and get evaluated and he can advise you to get a blood investigation done along with stool culture to rule out the exact cause of the symptoms and treat you accordingly.. As of now you should start with Fluid replacement therapy, taking plenty of oral rehydration salts, water and other fluids.. You can also take Ondensarton to reduce vomiting.. Take a soft diet and avoid fatty and spicy foods.. Hopefully it will get resolved with it but in case of no resolution you can be advised antibiotics for bacterial infection, anti spasmodics to relieve cramping and anti parasitics like Albendazole to relieve parasitic infection.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.