EPINEPHRINE, NOREPINEPHRINE, AND CORTISOL CONCENTRATIONS IN CANNULATED SEAWATER-ACCLIMATED RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) FOLLOWING BLACK-BOX CONFINEMENT AND EPINEPHRINE INJECTION

The present study investigates the effect of cannulation and chronic ' black-box' confinement, as well as epinephrine administration (4-0 mug kg-1), on the degree and time-course of alterations in trout (Oncorhy nchus mykiss) catecholamine and cortisol concentrations. Plasma cortis ol concentrations in seawater trout acclimated to 3-6-degrees-C reache d 104 ng ml-1 1 day after cannulation/confinement and remained elevate d above resting levels (8 ng ml-1) until 6 days post-confinement. Alth ough plasma epinephrine and norepinephrine generally declined over the period of confinement (day 1 approx. 12 nm; day 7 approx. 6 nm), nore pinephrine titres were usually higher and more variable. Epinephrine i njection caused elevations in plasma epinephrine levels but not in nor epinephrine levels; epinephrine titres reaching 107 +/- 26 nm (range 6 5-238 nM) at 2 min post-injection and returning to pre-injection level s by 30 min post-injection. Plasma cortisol increased by 20 ng ml-1 fo llowing epinephrine administration. Based on the time-course for post- confinement alterations in plasma cortisol, it appears that up to a we ek may be required before cannulated fish are completely acclimated to 'black-box' confinement. The findings suggest that meaningful results from experiments utilizing epinephrine injection and 'black-box' conf inement are contingent upon: (1) knowledge of circulating epinephrine levels shortly after injection (i.e. within 2 min post-injection); and (2) an experimental design that takes into account the elevated corti sol titres that are inherent with cannulation/confinement and epinephr ine injection.