I'm not going to let my husband use our cooking utensils for fish care
Why do you want to keep your husband away from the cooking utensils when he's doing fish care? Isn't that what they're for?
Because I don't want my husband to use the same utensils for cooking fishcare and cooking regular food.
Not wanting to have your utensils contaminated is pretty normal, but they can always be washed. You could have a conversation with him about washing the cookware after using it and this way you don't need to be so greedy with your things? It's always better to share with your spouse when you can.
My wants and needs are more important than his, I should be treated like a princess.
Ignoring people's needs and claiming yourself as more important is entitlement. People in relationships should be equal. Do you think he'd be happy to hear how you feel about his hobbies?