There are several possible reasons why a cat might vomit after eating shrimp:
Indigestion: If a cat eats too much shrimp, or eats undercooked shrimp, it may experience indigestion, leading to vomiting.
Allergic reactions: Some cats may be allergic to shrimp, which can cause vomiting. If your cat has an allergic reaction after eating shrimp, it is recommended to take it to a veterinarian.

Parasite infection: If a cat is infected with parasites, it may also cause vomiting. Regular deworming is recommended to ensure the cat's health.
Food poisoning: If shrimp is not fresh or is contaminated, cats may get poisoned after eating it, causing vomiting. Therefore, it is important to provide cats with fresh food and avoid letting them eat spoiled food.