Also, it was a movie. A movie made in 1963. The practice was probably legal then. And I hate to sound patronizing but, not everything you see in movies is real. If a scene in which two fish (I'll admit, it's been years since I saw it, do we even know, for certain, they were real fish?) fight to the death bothers you, you should probably not see a whole lot of other movies. Like ones where people fight to the death. Personally, I think being offended by a 41 year old movie for alleged animal cruelty is on the farther side of ludacris.
\Dan