The Effect of Oddity in Prey Selection of Largemouth Bass (Micropterus salmoides) Introduction The effect of oddity in predation is a very important factor when it comes to prey selection. A single “odd” fish is at a significant disadvantage when placed into a school of “normal” fish (Landeau & Terborgh 1986). The introduction of an “odd” fish may also make the “normal” fish more susceptible to predation. Schooling of prey, to avoid predation, causes the confusion effect in the predator, because they cannot single out one individual to pursue until capture (Landeau & Terborgh 1986, Pitcher & Parrish 1993). Objective To discover if largemouth bass show a significant preference for an introduced “odd” phenotype when accustomed to consuming the “normal” phenotype. Hypothesis Largemouth bass accustomed to feeding on the “normal” fish will show a preference for the “odd” phenotype when introduced. Materials and Methods Largemouth bass were purchased from a local hatchery. Fathead minnows (Pimphales promelas) and rosie reds (Pimphales promelas) were purchased from a local sporting goods store. Pilot studies were run to determine how many fish would be eaten per day and if the largemouth bass would consume both types of fish. All bass not being tested were kept in a 568 L holding tank until testing began When tested each bass was placed into a 95 L tank and given two days to become acclimated. Schools of eight minnows were used at a 1:1 ratio of fathead minnows and rosie reds. Each day the number of each type of eaten fish was recorded and the appropriate number of minnows was added to bring the school back to eight minnows at a 1:1 ratio Minnows were introduced into the tank using two clear two-liter soda bottles connected at the center with clear packaging tape, with rubber tubing attached to the top as seen in diagrams 1 and 2 (Jadlocki 2002). The experiment consisted of two parts Part 1 (n=22)– Fathead minnows (normal), Rosie reds (odd) - Bass were fed fathead minnows while not being tested. Part 2 (n=20)– Fathead minnows (odd), Rosie reds (normal) - Bass were fed fathead minnows while not being tested. Results Results cont’d Significantly more normal fish were eaten on day 1 of part 1 and part 2 when a paired t-test was run (P < part 1; P = part 2). The mean difference of fish eaten each day was only significantly different on day 1 of part 1 which was determined using a one-way ANOVA test (P = ). The mean difference of fish eaten each day was not significantly different for part 2 (P = , one-way ANOVA). A one-way ANOVA test was run on the total number of fish eaten each day for part 1 and 2. No significant differences were found in part 1, however, day one was significantly different in part 2 (P = ). Largemouth bass, on several occasions, ate all four “normal” fish. However, none of them ate all four “odd” fish. Conclusion Largemouth bass did not prefer the “odd” phenotype over the “normal” phenotype. Largemouth bass actually preferred the “normal” phenotype on day one of both parts of the study. Mean differences in some cases leveled out over the three day testing period suggesting that the bass may prefer the “odd” phenotype if the testing period is extended (5 days, 10 days, etc.) Literature Cited Landeau, L. and Terborgh, J Oddity and the ‘confusion’ in predation. Animal Behaviour 34: Pitcher, T. J. and Parrish, J. K Functions of shoaling behaviour in teleosts. Behaviour of Teleost Fishes (ed. T. J. Pitcher), pp 363 – 439. London: Chapman & Hall. Jadlocki, J.A Predators and the strength of preferences for familiar schools in the fathead minnow, Pimephales promelas. MENTOR: Rehnberg Acknowledgments Nathan Keller Department of Biology York College of Pennsylvania I would like to thank God for giving me the patience to complete this project. I would like to thank Dr. Rehnberg for helping me throughout my entire experiment Day Day 2Part Day Day Day 2Part Day 1 n c Standard Deviation Mean Difference b Difference a Total Eaten Table 1. Total number of fish eaten each day and difference between each phenotype, with respective Standard Deviation. Figure 1. Paired t-tests were run on the mean number of fish eaten each day to see if the means differed for part 1. Only day one differed significantly (P < ). Day two and three were not significantly different (day 2 P = , day 3 P = ). Part 1Part 2 Figure 2. Paired t-tests were run on the mean number of fish eaten each day to see if the means differed for part 2. Day one showed a significant difference (P = ). Days 2 and 3 showed no significant difference (day 2 P = , day 3 P = ) a red numbers indicate more rosie reds were eaten, and black indicated more fatheads were eaten b mean difference of fish eaten each day c sample size used Diagram 1Diagram 2