The problem is twofold: determining which species the fish belongs to, especially when they are fingerling/fry/eggs, and funding the process. It's not easy, and implementation won't be cheap. There's no way to implant a chip of any kind into fry and eggs, which means you're then increasing the costs and labor for the suppliers, since they have to raise the fish and feed them longer. The costs would shoot through the roof, reducing demand even lower. The numbers imported were ridiculously low, for the combined food, research and hobbyist industries. So how many hobbyists are really being denied something they wanted in the first place? This proposed legislation was very well published, and yet there were only a few people who submitted any sort of comment.
It's not like laws just magically appear. They are proposed, studied, published, discussed, and then voted on by the people elected to represent all of us. If a law makes it in that you disagree with, ask yourself if you did anything to impact the decisions one way or another. If you didn't, blaming the law makers is silly.