there have always been freak sized fish amongst what has come to be known as standard.
so its possible but they might also be not around anymore.
for example a lot of fishing record sizes for various species have been held for many years by the person that caught the monster. some of those specimens can be three times what is considered standard. though if you have untouched areas they still could hold fish that big. take a look at japanese koi for example. they started judging for size. so breeders bred from big genetics. after a few decades they began looking like little whales!