Habitat-, season-, and size-specific variation in diel activity patterns of juvenile chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss)

摘要: Juvenile salmonids that live in streams are sometimes nocturnal and may spend the day concealed stream substrate. We observed diel activity patterns of juvenile chinook salmon (Oncorhynchus tshawytscha ) steelhead trout mykiss) two areas Bridge River, British Columbia, all four seasons. In a reach with higher flows, most fish were year-round, they emerged from substrate only at dusk to forage. lower some active water column summer, but others remained until dusk. Parr older more summer than fry. All winter. Because our study design controlled for temperature photoperiod, we concluded differences behaviour between reaches due habitat conditions likely affected trade- off risky daytime foraging less efficient, safer, nighttime foraging. Habitat-driven variation will affect processes regulate these populations could make prediction effects ecosystem manipulations such as changes flow very difficult. Resume : Les saumons juveniles qui vivent dans les cours d'eau sont quelquefois nocturnes et peuvent passer la journee caches le substrat. Nous avons observe en toute saison profils journaliers d'activite de du Saumon quin- nat Truite arc-en-ciel anadrome deux sections ri- viere Colombie-Britannique. Dans section debits plus eleves, plupart des poissons l'annee ils ne quittent substrat qu'au crepuscule pour chercher leur nourriture. faibles, quelques s'activent colonne pendant ete, mais d'autres restent jusqu'au crepuscule. tacons âges ete que alevins. Tous hiver. Parce notre plan experimental permet tenir compte photoperiode, nous concluons comportement observees dues d'habitat affectent compromis entre quete nourriture jour perilleuse nuit sure, moins efficace. variations sous controle l'habitat vrai - semblablement processus assurent regulation ces populations; il peut alors devenir tres difficile predire effets l'ecosysteme, telles changements debit. (Traduit par Redaction) Bradford Higgins 374