Physiological and Behavioral Stress Responses of Walleyes Transported in Salt and Buffered-Salt Solutions

Abstract

To evaluate the value of transporting fingerling walleyes Stizostedion vitreum in buffered sodium chloride, we monitored blood chemistry, behavior, and water quality in conjunction with two 5-h transport trips. The control salt mixture was 0.50% sodium chloride (NaCl), and the buffered treatment was 0.45% NaCl and 0.05% sodium bicarbonate (NaHCO 3 ). We also collected posthaul blood samples from walleyes 2 h after they were placed into cages in East Okoboji Lake, as well as daily during a 72-h recovery period in hatchery raceways. Behavior was tested before and after hauls to quantify any disorientation that might occur as a result of hauling procedures. The addition of NaHCO 3 to hauling-tank water significantly increased the pH and alkalinity of the water compared with the unbuffered control. Overall, buffering produced significant effects on water chemistry but only minor effects on physiological measures of stress and the acid-base balance. In part, the effects of ram-air ventilation in removing excess CO 2 and the fact that the water had moderate alkalinity levels to begin with negated the beneficial effects of buffering. Buffering is likely to confer benefits in situations where is alkalinity is low and there is poor ventilation of the hauling tank. Before and after hauls, we tested the preference of walleyes for a black or white tank background with a simulated predator (black brush). In both hauls, before the haul fish in all groups chose a black background more often than the white background. After hauling, fish in the control group sometimes showed preference for a white background, but fish in the buffered water never showed a preference for a white background. Many fish stocked directly into the lake remained near the lake bottom close to the boat ramp for at least 5 h after stocking. The most conspicuous changes in blood chemistry occurred in fish 2 h after they were stocked into floating cages. Our results suggest that fingerling walleyes are disoriented following a 5-h haul and would benefit from a recovery period prior to stocking.

Physiological Responses of Walleyes to Live-Release Angling Tournaments

“…In general, walleyes sampled at tournaments showed greatly elevated plasma cortisol levels, especially when compared with the angled controls. It is noteworthy, however, that the cortisol levels in tournament walleye are within the same range as, or less than, those observed in walleye following other types of stresses (Barton and Zitzow 1995; Forsberg et al 2001; Barton 2002; Barton et al 2003). The plasma glucose levels of the tournament walleyes were also about double those of the resting laboratory control walleyes.…”

Effects of clove oil on the stress response of matrinxã (Brycon cephalus) subjected to transport

“…Several studies in freshwater fish have demonstrated decreased plasma chloride levels in animals subjected to transport (Barton et al, 2002;Forsberg et al, 2001;Mazik et al, 1991). A study with matrinxã showed that addition of marine salt (NaCl) to the water can also minimize the loss of ions during transportation (Carneiro & Urbinati, 2001).…”

Effectiveness of Walleye Fry and Fingerling Stocking in Rathbun Lake, Iowa, 1990–1999

“…Another factor that may have influenced survival was pond harvest and hauling stress, which have been demonstrated to cause immediate and latent mortality of stocked fish. Forsberg et al (2001) observed walleye fingerlings remained disoriented at the lake bottom near the boat ramp, after a 5 h haul, for at least 5 h after stocking. Intensively reared fish at the Rathbun hatchery required minimal handling and were stocked within one h after being loaded on the distribution truck, whereas extensively reared fish were seined, cribbed, loaded and hauled 6 h for 300 m. Hatchery personnel attempted to minimize stress, yet harvest and transportation of these fish was probably more stressful than that experienced by intensively reared fish.…”