Amanda Krull and Marie Havaich
This experiment was testing the foraging behavior of feeder goldfish (Carassius auratus auratus) with a predator present in the tank. The predator used in testing was a betta fish (Betta splendens). We wanted to test whether the foraging behavior of the feeder goldfish would be affected if there was a predator (betta) in the tank with them. We used brine shrimp (Artemia sp.) to calculate the amount foraged in each environment that was consumed by the feeder goldfish. We found that the feeder goldfish consumed significantly more brine shrimp in the tank without the predator present with a P-value of 9.62x10-6.
Key words: predation/predator, foraging, fish, consumption, prey
Feeder goldfish are normally the prey but in this experiment we wanted to test the foraging habits with a predator present. Feeder goldfish live in fresh water environments and brine shrimp were used to evaluate their consumption. Betta fish are a highly territorial fish that will attack other bettas, but they will also attack other fish that are brightly colored. Bettas live in environments that are very still and small. Because predator fish can impact foraging behaviors of potential prey we decided to test this by placing a feeder goldfish in the same tank as a betta to see any foraging changes took place (Soluk, 1993). The hypothesis we were testing is that the feeder goldfish will eat more brine shrimp when in the tank without the predator present, than the tank with the betta present.
We tested the feeder fish using three tanks brands unknown, a home tank (75.7 Liters), a beta tank (7.58 Liters) and a control tank (18.95 Liters). At first we placed the betta in a bag so it wouldn’t harm the fish but after further observation it did not seem to harm the fish so we placed it the water. Two fish were tested prior to the documented tests to ensure that the betta would not attack or injure them. After concluding that the test fish would not be injured we tested each fish individually for 5 minutes in both the predator and control tank. The betta was fed prior to testing to reduce his likeliness of consuming the brine shrimp. We documented the fish prior to testing and identified the color and size and any other outstanding markers to ensure we did not test the same fish twice. For each test in both tanks 5 brine shrimp were used. The fish were observed for the full 5 minutes in each tank and the amount of brine shrimp consumed was documented. We started with 25 feeder fish and tested 16 fish in all, after casualties in the home tank and removal of 2 initially tested fish. We used a 2-tailed type 1 T-test to determine if the difference in consumption was significant.
After using a 2-tailed T-test we found there was significantly less brine shrimp consumed in the betta tank than without. Our p-value was 9.62x10-6 showing there was a significant difference. We used the means of the brine shrimp consumed in each tank and input it into a bar graph with standard deviation error bars (Fig.1). The mean amount of brine shrimp eaten in the tank with the betta was 0.56 (SD=0.629) and the mean amount eaten in the control tank was 3 (SD=1.506).
Fig. 1 the mean amount of brine shrimp consumed with and without predator presence (error bars-standard deviation).
Our hypothesis was supported that feeder goldfish foraged more brine shrimp when they were in a tank without a predator present rather than with. We used previous research with the brook char which identified changes in foraging behaviors with a predator present (Salvelinus fontinalis), when predators were within the proximity of the fish (McLaughlin et al., 1999). We infer that if we were to test the feeder fish in groups of 2 or more our p-value may have diminished, therefore we chose to test only one fish at a time. One thing that may have had an influence on our results was the different size in the control and the test tanks. When the feeder fish were in the tank with the predator most did not attempt to go after the brine shrimp but a small number did. They were continuously watching the Betta, and moving very infrequently unless the Betta neared them. Some of the feeder goldfish made no attempt to catch the brine shrimp even when they were right in front of them, but a small number would attempt to eat some of the brine shrimp. We infer this was because the betta was much larger than the feeder fish. It has been observed that a predator directly affects the foraging behaviors of their prey when in the same environment (Godin et al., 1994). We found that the feeder fish did consume greater amounts of brine shrimp when in the tank without the betta compared to the one with the betta present. If we were to redo this experiment we have the test and control tanks be the same size.
Godin, J.G.J, and Crossman, S.L. (1994). Hunger-Dependant Predator Inspection and Foraging Behaviours in the Threespine Stickleback (Gasterosteus aculeatus) under Predation Risk. Behavioral Ecology and Sociobiology, Vol. 34, No. 5 pp. 359-366. Retrieved on March 24th, 2009 from: Jstor
McLaughlin, R.L., Ferguson, M.M., and Noakes, D.L.G. (1999). Adaptive Peaks and Alternative Foraging Tactics in Brook Charr: Evidence of Short-Term Divergent Selection for Sitting-and-Waiting and Actively Searching. Behavioral Ecology and Sociobiology, Vol. 45, No. 5 pp. 386-395. Retrieved on March 24th, 2009 from: Jstor
Soluk, D.A. (1993, January). Multiple Predator Effects: Predicting Combined Functional Response of Stream Fish and Invertebrate Predators. Ecology, Vol. 74, No. 1 pp. 219-225. Retrieved February 8th, 2009 from: Jstor