Biology prof discusses fish predator research

Biology professor Brian Wisenden talks about predator avoidance Wednesday in the Science Lab Building.

Biology professor Brian Wisenden talks about predator avoidance Wednesday in the Science Lab Building.

This year’s Dille distinguished faculty lecture was both informative and thought provoking. Marking the 17th anniversary of the event, biosciences professor Brian Wisenden gave a talk entitled “Cichlids and Minnows and Worms. Oh My!
The Behavioral Ecology of Predator Avoidance.”

Wisenden has taught at MSUM since 1998 after earning degrees from multiple universities in Canada. He currently has 80 publications, along with 10 individual book chapters and one entire book.

The lecture was based on research Wisenden and a group of undergraduate students from both MSUM and the University of Minnesota conducted from three sites across the globe: Rio Cabuyo, Costa Rica; Laguna de Xiloa, Nicaragua; and Itasca State Park in Minnesota.

Starting off the lecture, Wisenden said, “I’m going to begin by showing you where my passion began.” He then played a video of cichlids, a perch-like fish found in Costa Rica, Nicaragua and other tropical places. Unlike most fish, cichlids continue to care for their young after they have hatched. Wisenden explained his objective in studying the fish, saying that he was interested in both the parent’s and offspring’s natural predator avoidance techniques.

He and a group of students observed how the cichlids in Costa Rica defended their young. They looked at the distance the young cichlids were willing to swim away from their parents in relation to their body length. Wisenden and the students also examined 111 skeletal elements of the young fish, paying close attention to when each bone calcified.

From there the group of researchers went to Nicaragua to compare their findings to other cichlids in a different part of the world. Specifically, they wanted to know if there was a correlation between the time bones calcify and the distance the young would stray from the parents. After conducting the same tests, the results were slightly different.

Because predators are much more intense in Nicaragua compared to Costa Rica, Wisenden and his team discovered that Nicaraguan cichlids swam much closer to their parents and were later in developing calcified bones as compared to Costa Rican cichlids of the same length. From these findings, the team of researchers determined the young fish were using their energy to grow, rather than convert their bones from cartilage to calcium. Since a larger size gives them more advantage to escape a predator attack than developed bones, the results made sense.

The study did not end there. Looking at minnows from Itasca State Park, Wisenden and the students still had some unanswered questions about predator avoidance.

The researchers conducted many tests using chemical alarm cues, such as skin extract, to test recognition of predators. Much like the famous Pavlov’s dog study, Wisenden said, “We can teach them to be afraid of anything by giving them a neutral stimulus with alarm cues. They associate fear with that new thing.”

That new thing for Wisenden’s team was anything from a black disk to a tube. Not only did they introduce an alarm cue such as smell, but they also used movement or stillness of an object as well. Similar tests were done to walleye and even embryos. The ability to train any fish, at any stage of its life, to be afraid of predators is not only intriguing, it could also be useful. Teaching a species of fish that is endangered to avoid predators and thus live longer to have more young would be a solution to saving fish from possible extinction.

Along with predators, Wisenden and his students conducted similar tests to see if fish could be trained to avoid a parasite infestation. The results showed they could be taught to avoid them just the same as predators.

The last, and perhaps most fascinating, question Wisenden addressed was whether fish have personalities and if that could be a factor in the response to alarm cues.

The group set traps, some containing a sponge soaked in an alarm cue smell and others soaked in water. While the trap soaked in water held many more fish, the one containing the alarm cue had captured a few. When tested a second time, the same fish again swam into the dangerous smelling trap rather than the safe one. Wisenden wanted to know if it were possible that fish could have a bold or meek personality.

That question lead to the invention of the first fish personality test: a series of large and small tubes, both bent and straight. The test results showed the same fish who had swam into the dangerous trap were the ones who also went through every tube, regardless of size or shape.

Taking the hypothesis one step further, the team of researchers bred and tested the offspring of the fish. They found the father’s personality type made no difference in the personality of the young. The mother was the determining factor. The type of eggs a bold female makes compared to a meek female are different, yielding different offspring.

With that final revelation, Wisenden ended his lecture saying, “Science is a verb; it is a method. You have to do science.”

Then, Michelle Malott, dean of the College of Science, Health and the Environment and MSUM provost Ann Blackhurst presented Wisenden with an honorarium and commemorative clock.


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