Q and A

Q. In the late 1940's I fished a lot for smallmouths on the Potomac about 50 miles upriver from Washington, DC. Casting a small plug about the length of your ring finger and 3/16 ounce weight. Bass jumped on it. For about four years the lure was terrific--then it became just another decent lure that the bass often ignored. I watched  the same thing occur with plastic worms, then Mister Twister-type lures, then Rapala, and so on. The same thing has happened in the Keys with tarpon and bonefish. I can think of many other examples of this pattern with many different gamefish in fresh and saltwater. What do you think causes this?

A I can think of many things to explain your experience, but I address below what I think are the two mostly likely explanations (these are not mutually exclusive).

The first potential reason is learned behavior. Fish that eat a certain lure or fly and are released may retain a bad association with that lure, and this would cause them to not eat that lure in the future (or be less likely to do so). This would be the same reaction a fish would have after eating a natural organism that is poisonous – if they recognize a characteristic of that organism that they associate with ‘negative’ they are less likely to eat that organism in the future. This is one reason that some of the more noxious organisms are brightly colored – an easy to recognize warning that deters predation. I think that bass and other fish can and do react to lures in the same way. After all, our lures and flies are imitating prey of some sort, so the fish react to them in a similar fashion (whether they eat them or refuse them). You see this change in reaction to lures and flies a lot in catch and release fisheries. In some situations it might not even be a lure or fly that causes a negative association, it might be boat noise or other variables, but the other variable is associated with the presence of a lure or fly. To some extent, this is a reason that smaller fish tend to be more aggressive (and easier to catch) than larger fish in areas that receive fishing pressure – the smaller fish haven’t learned yet. In areas that don’t receive much fishing pressure, it’s common for the large fish to be just about as aggressive as the smaller fish. To a certain extent, the longer-lived the fish, the more likely that learned behavior will be a factor. Tarpon can live up to 80 years, for example, so have a long time to figure things out. Bonefish can live at least 20 years, again a long time to have experience with flies.

The second reason could be the loss of fish that ate those lures (or lures in general). These were mostly the more aggressive fish, and this aggression may have been a genetically based trait. These fish would be lost due to harvest or to their death after release. In this scenario, in the early days of little or no fishing pressure, the more aggressive fish that tended to eat more than the other fish would attack the lures and flies. Over time, as these fish were removed from the population, the aggressive genes would become less prominent, and the population would become dominated by less aggressive feeders. In this scenario, there is a higher survival rate of fish that wouldn’t eat those lures (or colors) or are less aggressive. Since more of these less aggressive fish survive and produce offspring for the next generation in comparison to the more aggressive fish, the genes for being less aggressive (or for a preference against certain colors, etc) are passed on to the next generation. This may create a population that is less aggressive toward all lures or flies, or a population that reacts negatively to a certain color, etc.

A final (depressing) reason is that in many cases there are considerably fewer fish than there were in previous years. So in locations where there were once 10 fish competing for food and charging the lure to be first to eat, there now may be 3 fish.

Of course, in many cases it is a combination of these scenarios that act to change fish reactions to lures and flies, as well as when and how fishermen select and use lures and flies.