Greetings FishTalkers, welcome to an utterly awesome time of year. Tidal action is getting ready to bust wide open, the freshwater fish are snapping, and now on some days we can once again enjoy the bite we like in a T-shirt. Woohoo!

Sometimes we examine important issues, fisheries matters, or regulations in the Notes column, but this is not such a month. Instead, I have a question to ask y’all: Are the fish getting smarter?

holding a yellowfin tuna
Just what eactly is going on inside that fish's pea brain?!

I recognize that on the surface of things, this sounds downright ridiculous. But we do know for a fact that in heavily-fished bodies of water some species can become conditioned to particular types of popular lures, and will stop hitting them. And some of the fish behavior we’ve seen in recent years seems mighty suspicious. Consider:

  • 30 years ago bluefish would slam any bait, regardless of hook placement or the presence of wire leaders. Today they seem to have an amazing talent for biting off chunks of a fish or bait without ever taking the hook into their mouth — sometimes even biting off a spot’s head and tail, while mysteriously “missing” the middle section with a hook.
  • 30 years ago if you approached a school of rockfish busting on the surface with your boat at slow speed, quietly, then shifted into neutral, the school would usually remain at the surface while you caught one fish after the next. Today, when you get within 100 yards the school almost always seems to sound at the first hint of approaching boat noise, regardless of how fast you’re moving or how stealthy you may be.
  • 30 years ago chunking for yellowfin and bluefin tunas with 80-, 100-, or even 120-pound test was the norm and those fish ate the chunks without hesitation. Today, it’s often tough or impossible to get a bite using anything over 30-pound fluorocarbon.

If we were only talking about fish that were 30-plus years old, it might seem reasonable that the more intelligent fish in a school would learn that hooks, boat noise, and visible leaders are dangerous. But we’re not. This goes for the 20-inchers as well as the larger, older fish. So, what gives? After all, there’s no way on Earth that the fish are actually getting smarter. Or, is there…?

A fascinating study published by University of Otago researchers posits the idea that fish may, in fact, be capable of inter-generational learning. The reason? Fish have “DNA methylation.” One of the study authors, Dr. Oscar Ortega-Recalde (who earned his PhD researching transmission and reprogramming of epigenetic information) explains it like this:

“Methylation sits on top of DNA and is used to control which genes are turned on and off. It also helps to define cellular identity and function. In humans and other mammals, DNA methylation is erased at each generation; however, we found that global erasure of DNA methylation memory does not occur at all in the fish we studied.”

Wow. Like, WOW!

Dr. Tim Hore, another author of the study, says “Mammalian biologists have searched long and hard to find reliable examples of where altered DNA methylation patterns are passed on to subsequent generations; yet only a handful have been verified in repeated studies. However, unlike humans, DNA methylation is not erased at each generation in at least some fish. So, we think intergenerational memory transfer through DNA methylation could be much more common in fish.”

And if you’re not yet convinced, also published in “Nature” was a complementary study from the Garvin Institute in Australia, confirming the findings.

So, is it remotely possible that the fish actually are getting smarter? Could their instincts be evolving? Strange though it may sound, maybe so.