Faculty Mentor

Paul Spruell

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Two stocks of Bull Trout (Salvelinus confluentus) were tested in a two choice Y-maze to determine if they could detect pheromones from the same natal population (population specific pheromones PSP) or from a different (conspecific) population of Bull Trout (CSP). Fish from the Pack River (PR), Idaho and the Metolius River (MR), Oregon were transferred to a fish hatchery where Y-maze studies were conducted. The Y-maze was constructed to supply well water at 12°C (blank) to both arms with the temperature and discharge of each arm matched to within 0.1°C and 0.01 l/s. One arm was randomly selected to be supplied with pheromones from fish held in stock tanks. Four types of tests were conducted with each stock: 1) blank supplied to both arms; 2) PSP + blank in one arm; 3) CSP + blank in one arm; 4) PSP + blank in one arm and CSP + blank in the other. Chi Square (χ²) Goodness of Fit tests with two degrees of freedom were used to compare the frequency at which fish entered each arm to the theoretical distribution that assumed they randomly selected an arm. Both stocks exhibited no preference when blank water only was present [PR: (χ²=4.79; p=0.091; n=28); MR: (χ²=4.67; p=.097; n=27)]. Both stocks preferred the PSP arm over the blank arm during PSP tests [PR: (χ²=14.00; p<0.001; n=27); MR: (χ²=21.94; p<0.001; n=28)]. Both stocks preferred the CSP arm over the blank arm during CSP tests [PR: (χ²=15.07; p<0.001; n=26); MR: (χ²=16.72; p<0.001; n=31)]. During the PSP vs. CSP tests, both PR and MR spent equivalent frequency in PSP and CSP arms therefore exhibited no preference [PR: (χ²=2.96; p=0.227; n=29); MR: (χ²=4.90; p=0.086; n=31)]. These results showed Bull Trout could detect pheromones from other Bull Trout but could not differentiate between PSPs and CSPs.