There's enough stomach acid to dissolve a hook. Fear not, Dan - that cat is fine.
Agreed. I did a science project for school once, driving a 16p sinker nail into a coke can and observe the results. In about 2 weeks, the nail fell over, the bottom half gone. The acid in the soda was that strong, yet I drink 4-5 every day. Stomach acid is stronger by an order of magnitude, in mammals
the fish should be fine. (Imho)
