Impact of Low-Level Sampling Stress on Interpretation of Physiological Responses of White Sucker Exposed to Effluent from a Bleached Kraft Pulp Mill

In this study the authors evaluated the effects of handling and confinement stress on a number of biochemical parameters in prespawning male white sucker collected from a bleached kraft mill effluent (BKME) exposed and a reference site. There were no effects of site or stress level on plasma cholesterol or glutamic oxalacetic transaminase activity; all other parameters were affected by either sampling stress or overnight confinement. Unstressed BKME fish reflected higher levels of plasma lactate, and lower levels of plasma testosterone, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one, and cortisol. Acute handling stress or overnight confinement created a site difference in plasma glucose, protein, and 11-ketotestosterone, reversed the site effect for plasma lactate, and eliminated site differences for 17 alpha,20 beta-dihydroxy-4-pregnen-3-one. Since it is very difficult to standardize capture and handling stress in field studies impacted by industrial effluents, biochemical differences must be interpreted carefully. This study has also demonstrated for the first time that BKME exposure resulted in reduced circulating levels of the stress steroid cortisol, similar to the decreases in reproductive sex steroids previously reported.