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A vertical slot fishway and two Denil fishways (of 10 and 20% slope) built into a weir on the Lesser Slave River (55°18′N, 115°45′W) were studied from May 12 to June 25, 1984, to determine how effectively these designs pass north-temperate, nonsalmonid fishes. Thousands of spottail shiner (Notropis hudsonius), substantial numbers (> 100) of northern pike (Esox lucius), longnose sucker (Catostomus catostomus), white sucker (Catostomus commersoni), immature yellow perch (Perca flavescens), and lesser numbers of burbot (Lota lota), adult yellow perch, lake whitefish (Coregonus clupeaformis), and trout-perch (Percopsis omiscomaycus) ascended the fishways. Walleye (Stizostedion vitreum) and goldeye (Hiodon alosoides), although probably moving extensively through the river, did not use the fishways. Although high water levels allowed most fish to surmount the weir, of those that chose the fishway, pike strongly preferred to ascend the Denil fishways and the two sucker species preferred to ascend the vertical slot. Therefore, a combination of several different fishways may be required for the most efficient passage of a wide variety of species. Plasma glucose and lactate measurements on pike revealed that ascending the Denil fishways was only moderately stressful for these fish.

Changes in blood lactate, pH, Pco2, and plasma [Formula: see text] and glucose were measured during recovery from exercise–handling stress in chronically cannulated northern pike (Esox lucius L.). Exercise was induced by lifting pike out of water (three 30-s periods of emersion alternated with 30-s periods of water submersion), while they were inside tubular plastic chambers. Large depressions in blood pH and plasma [Formula: see text] occurred within minutes after exercise. Initially, the acidosis was of mixed respiratory (elevated Pco2) and metabolic (H+ release from the muscle) origin. Although the respiratory acidosis was corrected in 2 h, 8 h was required to return blood pH to preexercise levels. A large accumulation of lactate anion in the blood occurred after exercise, the increase by 2 h (12.8 mmol L−1), being approximately equal to the metabolic acid load. These results conflict with previous reports on muskellunge (Esox masquinongy M.), in which blood lactate elevation following exercise was small (2.5 mmol L−1) and greatly exceeded by the metabolic H+ load (7.0 mmol L−1). By 2 h after exercise the plasma glucose level of pike had increased by 8.8 mmol L−1 and the return to preexercise levels was almost complete by 12 h. Intraarterial infusion of a large sodium lactate load elevated plasma glucose level by only 1.7 mmol L−1, indicating that postexercise hyperglycemia in pike is a response to stress and not simply a consequence of lactate removal by conversion into glucose.

Abstract. Seasonal changes in the fatty acid composition of neutral and polar lipids were measured in the ovary, liver, white muscle, and adipopancreatic tissue of northern pike. The role of environmental and physiological factors underlying these changes was evaluated. From late summer (August-September) to winter (JanuaryMarch), the weight percentage of n-3 polyunsaturated fatty acids (especially 22: 6n3) declined significantly in the neutral lipids of all somatic tissues examined. However, large quantities of n-3 polyunsaturated fatty acids accumulated in the recrudescing ovaries during fall and the weight percentage of n-3 polyunsaturated fatty acids in ovary polar lipids also increased significantly. Additionally, the n-3 polyunsaturated fatty acid content of somatic polar lipids increased significantly during fall due to increases in the total polar lipid content of the somatic tissues. This suggests that during fall n-3 polyunsaturated fatty acid, are diverted away from somatic neutral lipids and thereby conserved for use in ovary construction and for incorporation into tissue polar lipids. The percentage of n-3 polyunsaturated fatty acid in ovary neutral lipids also declined during fall and early winter, perhaps as an adaptation to conserve these fatty acids for storage in oocyte polar lipids and later incorporation into cellular membranes of the developing embryo. Reductions in the n-3 polyunsaturated fatty acids content of somatic and ovarian neutral lipids during fall were compensated for specifically by increases in the percentage of monounsaturated fatty acids rather than saturated fatty acids. This suggests that the ratio of saturated to unsaturated fatty acids in pike neutral lipid, is regulated physiologically, and hence may influence the physiological functioning of these lipids. During fall and early winter the percentage of saturated fatty acids declined significantly in the polar Abbreviations: AP, adipopancreatic; BHT, butylated hydroxytoluene; CI, confidence interval; EFA, essential fatty acids; MUFA, monounsaturated fatty acids; NL, neutral lipids; PL, polar lipids; PUFA, polyunsaturated fatty acids; SFA, saturated fatty acids Correspondence to: K. Schwalme, Alberta Environmental Centre, Bag 4000, Vegreville, Alberta, Canada, TOB-4L0 lipids of all tissues examined. This change was consistent with the known effects of cold acclimation on the fatty acid composition of cellular membranes. As the ovaries were recrudescing from September to January, liver polar lipids exhibited significant decreases in the percentage of total polyunsaturated fatty acids and n-3 polyunsaturated fatty acids and increases in monounsaturated fatty acids, and acquired a fatty acid composition very similar to that of ovary polar lipids. Therefore, seasonal changes in the percentage of polyunsaturated and monounsaturated fatty acids in liver polar lipids probably reflect the liver's role in vitellogenesis rather than the effects of temperature on membrane fatty acid composition. At all times of year, the fatty acid com...

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