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BEHAVIOR AND PHYSIOLOGY OF MARKED FISH 100 ?-A multiple shock •- •• single shock ah ?Aa A--o30 s handling 80 i .\ 0• • • O control 60 \ '- bj ?c 1 40 bAp. . • ? O 20 dc 100 O 7 E O T T O_ 1001 U Q U 80 U , 60- a? \ A \ a 40 ?.. 0 20 bb r 0 -,-I I I I T T? 0 1 3 6 12 24 16a 655 TIME (h) FIGURE 8.-Mean plasma lactic acid concentrations in unstressed Cedar Creek Hatchery cutthroat trout and in fish subjected to a single 8-s, 500-V-DC electroshock; three 8-s, 500-V-DC electroshocks separated by 0.5 h; or a 30-s handling stress. Upper and lower panels represent first and second replicate trials, respectively. Means (N = 5) within a time interval with no letters in common are significantly different (P < 0.05); time intervals with no letters shown indicate no significant difference among the means. Vertical bars represent 1 SE. we observed distinctly abnormal behavior in one section, most fish remaining in the other sections after successive electrofishing passes were showing the characteristic normal behavior of Mill Creek fish. However, because the depletion method is popular in small streams and multiple electro- shocks affect fish physiology, the effect of multiple shocks on fish behavior may warrant further in- vestigation. Exposure of fish to electricity plus handling, marking, or other physical disturbance subjects them to a substantial amount of stress that leads to changes in blood constituents (Schreck et al. 1976; Burns and Lantz 1978; Bouck et al. 1978). Schreck et al. (1976) attributed these changes to the combined effects of trauma, paying off an oxy- gen debt, and the general adaptation syndrome of stress. Cutthroat trout subjected to a single elec- troshock did not show an immediate (i.e., < 10 s) increase in plasma cortisol and lactic acid. This is consistent with the results of Woodward and Strange (1987) for rainbow trout but contrasts with those of Schreck et al. (1976); however, a rela- tively longer time period elapsed before Schreck et al. (1976) collected their first samples. In our study, lactic acid typically returned to control levels after 3 h, whereas cortisol required 6 h. The ad- dition of stressors involved with the mark-recap- ture procedure immediately elevated concentra- tions of plasma cortisol and lactic acid beyond levels observed in fish experiencing only electro- shock. Perhaps fish that were electroshocked and marked simply had more time to liberate cortisol from the interrenal tissue. The stressful experience