"Will Trout Eat Live Food?" Experiment and Conclusions

 

Throughout January, Trout in the Classroom Visit # 3 has looked like students following the Scientific Method to answer the question- "Will trout eat live food?"

After asking the question, students assessed background information about the trout in order to inform their hypothesis on whether or not trout will eat live food. They examined the food the trout are already eating, recognizing the fish flakes contain fish particles and learned that trout are in fact carnivores. This at least indicated that daphnia, a type of zooplankton, was within the realm of what a trout would eat.

But since this was the first time introducing trout to zooplankton, there was uncertainty on how the trout would react. Would they eat the daphnia? If so, how many? And how much or little time would it take for the trout to eat the daphnia?

Students developed their hypothesis by completing the sentence, "If I add daphnia, then my trout will...." Across many classrooms visited in the past few weeks, the range of hypothesis' created were: "eat all of the daphnia right away," "be scared of the daphnia and run away," "take a bite of the daphnia and see if they like it first," "wait a few minutes to get used to the daphnia and then eat them."

In the beakers, the daphnia was added and the experiment started. Students watched diligently, as one student took on the role of "master recorder," and would make sure within every 20-second interval, the number of daphnia eaten was recorded until the end of the time period (anywhere from 3-5 minutes, depending on the class.)

After the experiment was over, table groups came to a consensus on the tally of daphnia eaten. Afterwards, groups presented what they expected to happen vs. what actually happened. Some predictions were somewhat close to the outcomes, some nowhere near. The students came up with theories to draw conclusions as to why their trout ate more or less daphnia than expected. 

In the case where trout ate more daphnia than expected, conclusions drawn were that maybe the trout was hungry, or it was scared of the daphnia so ate them up, or it instinctually knew to eat live food, or that the trout had learned the behavior of eating food that was dropped from up above. 

For students who experienced less daphnia eaten than expected, conclusions drawn were that maybe the trout was already full from previous feeding that day, or had already been selected in prior classes to eat daphnia. Students also theorized that the trout was uncertain of this new animal and didn't want to engage. Or in some cases, the trout ate one daphnia but perhaps realized they didn't like it.  

At the end, the classes were brought back to the original question- "Will trout eat live food?" or more specifically, "Will trout eat live food when they are released in the streams in the spring time? Will they survive?" 

Students gave thumbs up for "yes" and thumbs down for "no." Results were mostly positive. But most opinions were based on the data collected at each independent table. Students were less likely to believe their trout would survive if it did not eat the daphnia during the experiment, and more likely to believe the trout would survive if the trout did eat some or a most of the daphnia. In the end, it all came down to the data!