Metabolic enzyme activity during smolting in stream- and hatchery-reared Atlantic salmon (Salmo salar)

To evaluate the metabolic differences between Atlantic salmon (Salmo salar) parr and smolts and the effect of rearing environment, we examined metabolic enzyme activity in white muscle, liver, and heart in streamand hatcheryreared juveniles. Spring increases in gill Na+,K+-ATPase (3.5-fold) and cardiosomatic index (37–69%) and decreases in condition factor (~17%) occurred in smolts, but not in parr. White muscle phosphofructokinase (PFK) increased during spring and was 3.6-fold higher in smolts than in parr by late spring. There were seasonal increases in liver citrate synthase (CS) (~42%), liver b-hydroxyacyl-coenzyme A dehydrogenase (HOAD) (~60%), and heart CS (~23%) and decreases in liver lactate dehydrogenase (LDH) (~28%) in parr and smolts. Activity of liver HOAD was greater in stream-reared smolts (~18%) than in parr or hatchery smolts. Heart PFK activity increased during spring in wild-reared parr and smolts, while it decreased in hatchery-reared smolts. White muscle LDH and PFK increased earlier in spring in hatcherythan in stream-reared smolts. Our results suggest that increased heart size and high white muscle PFK occur during smolting and may be adaptive for downstream and ocean migration. Hatcheryand stream-reared Atlantic salmon differ in the timing of metabolic changes during smolting, which may impact their long-term survival. Résumé : Un examen de l’activité des enzymes métaboliques du muscle blanc, du foie et du coeur chez des jeunes Saumons de l’Atlantique (Salmo salar) élevés en ruisseau et en pisciculture a été entrepris pour évaluer les différences métaboliques entre les tacons et les saumoneaux et les effets du milieu d’élevage. Au printemps, la Na+,K+-ATPase des branchies augmente de 3,5 fois et l’indice cardiosomatique de 37–69%, alors que le coefficient d’embonpoint diminue (~17%) chez les saumoneaux, mais pas chez les tacons. La phosphofructokinase (PFK) du muscle blanc augmente au printemps et elle est 3,6 fois plus élevée chez les saumoneaux que chez les tacons à la fin du printemps. Il y a des augmentations saisonnières de la citrate synthase (CS) du foie (~42%) et du coeur (~23%) et de la b-hydoxyacylcoenzyme A déshydrogénase (HOAD) du foie (~60%) chez les tacons et les saumoneaux, ainsi qu’une diminution de la lactate déshydrogénase (LDH) du foie (~28%). L’activité de la HOAD du foie est plus grande (~18%) chez les saumoneaux de ruisseau que chez les tacons ou les saumoneaux de pisciculture. L’activité de la PFK du coeur augmente au cours du printemps chez les tacons et les saumoneaux sauvages, mais elle diminue chez les saumoneaux de pisciculture. La LDH et la PFK du muscle blanc augmentent plus tôt chez les saumoneaux de pisciculture que chez les saumoneaux de ruisseau. Nos résultats indiquent que, durant la saumonification, la taille du coeur s’accroît et la PFK augmente dans le muscle blanc, ce qui pourrait être des adaptations pour la migration vers l’aval et l’océan. Les Saumons de l’Atlantique élevés en pisciculture et en ruisseau diffèrent dans la phénologie de leurs changements métaboliques durant la saumonification, ce qui peut affecter leur survie à long terme. [Traduit par la Rédaction] 1593 Leonard and McCormick Introduction Alteration of metabolism during the parr–smolt transformation has been found in several salmonid species. In Atlantic salmon (Salmo salar), standard and active metabolic rates are 50% higher in smolts than in parr (Maxime et al. 1989). Maxime et al. (1989) suggested that this elevation of metab lic rate in smolts might be due to elevated respiratory enzyme activity and mitochondrial proliferation resulting from an increase in thyroid hormone levels. Metabolism may also increase due to the metabolic demands of development and differentiation (McCormick and Saunders 1987). Atlantic salmon smolts have decreased available liver and muscle glycogen compared with parr (Fontaine and Hatey 1953; Can. J. Fish. Aquat. Sci. 58: 1585–1593 (2001) © 2001 NRC Canada 1585 DOI: 10.1139/cjfas-58-8-1585 Received May 15, 2000. Accepted April 26, 2001. Published on the NRC Research Press Web site at http://cjfas.nrc.ca on July 11, 2001. J15761 J.B.K. Leonard1,2 and S.D. McCormick. Conte Anadromous Fish Research Center, Biological Resources Division, U.S. Geological Survey, Turners Falls, MA 01376, U.S.A., and Department of Biology, University of Massachusetts, Amherst, MA 01003, U.S.A. 1Corresponding author (e-mail: [email protected]). 2Address for correspondence: Department of Biology, Northern Michigan University, 1401 Presque Isle Avenue, Marquette, MI 49855, U.S.A. J:\cjfas\cjfas58\cjfas-08\F01-105.vp Tuesday, July 17, 2001 7:12:17 AM Color profile: Disabled Composite Default screen