Why are Fish so Dumb?

We spent an afternoon fishing (and releasing) off a dock in a small lake in Vermont. Over the course of two hours we must have reeled in a fish at least twenty times. After a while the kids realized that we seemed to be catching the same three fish(es?) over and over. Why didn't they learn? Yes there was a wiggly delicious worm appearing like magic from above, but at some point one would assume that they would get suspicious. Are fish ridiculously optimistic or just plain stupid?

There are a lot of theories about memory in fish, few of which can be proven. A persistent myth is that fish can only remember something for three to eight seconds - Dory from Finding Nemo certainly helped perpetuate it. The Dory theory would help explain why the same fish keep biting.  But Culum Brown, a researcher at the University of Edinburgh, begs to differ.  According to Brown, fish can be trained to escape a net and can retain that information over many months rather than just moments. They also use tools to forage, build nests for their young, have social structures and, in larger schools, can pass learning down through generations (yeah, that's kinda punny.) This is interesting, but sadly fails to explain why the fish keep biting. My theory would be that in spite of all of the evidence about the intelligence of fish, when food drops from above, instinct takes over and they just can't help themselves.

Another interesting bit of research seeks to explain why farm or hatchery fish lack the "stream smarts" of their wild counterparts. From an old article in the LA Times:

The wild trout spend most of their time under ledges or other cover. They retreat back to the cover after they snatch food. They swim near the bottom of the tank, and conserve energy by resting where the current is weakest. They travel alone.

The hatchery trout ignore cover. They swim near the surface, where they would be easy prey for birds. Sometimes they stick their fins out of the water. They waste energy by fighting currents. They swim in schools.

So, many fish are smart and some fish are genuinely dumb, but once again, we fail to explain catching the same fish over and over again especially considering that the ones we were catching were wild.

Perhaps in our tiny lake the social structure and etiquette among the fish are so developed that they have been strenuously taught never to look a gift horse in the mouth. Sure that's probably the polite thing to do, but it didn't work out so well for the Trojans either, now did it?

NOTE: I was surprised to learn in researching this that the "gift horse" adage was not in fact a reference to the Trojan Horse (it would have been devastatingly bad advice to them anyway) but simply advice that one should avoid critically examining gifts for flaws. I never really understood that one until now, because I always thought it referred to the most famous gift horse in history. Who knew?

NOTE TWO: Fish and fishes are both acceptable as the plural of fish, according to Merriam-Webster.