So neither pure fish based nor pure plant based, but rather a combination of the two. Also one could occasionally eat other wild animals obtained via hunting, like deer.
Right, but you got to acknowledge that dogs and cats are a far more available in cities. Just because you have the privilege of easy to kill fish you can not blame others for killing wild dogs and cats. Cats kill so much birds, it is much better for the environment to kill them instead of fish.
I don't need to jump in a lake for the same reason I don't need to operate a farm. It is equally moral if others do it for me, so I buy wild fish and vegetables from my grocery just like most people.
Also, pure veganism isn't necessary. For example, honey is not vegan but producing honey likely kills fewer animals than producing almonds. Beekeeping might even be a net positive given the benefits to the ecosystem at large