Stream Temperatures and Inter-Annual Variability in the Emigration Timing of Coho Salmon (Oncorhynchus kisutch) Smolts and fry and Chum Salmon (O. Keta) Fry from Carnation Creek, British Columbia

Abstract

1989. Stream temperatures and inter-annual variability in the emigration timing sf coho salmon (Onesrhyncdaus kisutch) smolts and .fry and churn salmon (0. keea) fry from Carnation Creek, British Columbia. Can. 8. Fish. Aquat. Sci. 46: 1396-1405 Variability in average stream temperatures between peak spawning and fry emergence accounted for 82 and 77% of the variance in the median emigration date sf fry of chum (Oncorhynchus keta) and coho salmon (0. kisutch), respectively, over a 9 to 10-yr period. The modeled relationships were indistinguishable from laboratory models that predicted time to rnaxirnyrn alevin wet weight. Variability in stream temperatures during the spring accounted for 60% sf the variability in the median date sf coko srnolt emigration. As stream temperatures increased, the predicted thermal surnrnati~ws required for emigration were nearly constant for coho salmon fry, increased moderately for churn salmon fry and increased strongly for coho salmon srncplts. The duration of the emigration period also differed between the groups: 50% of the churn salmon fry emigrated aver a I-wk period compared with a 2-to 3-wk p e r i d for coho salmon fry and smolts. We speculate that the emigration timingtemperature relationships and timing of adult spawning represent adaptations for synchronizing emigration with "windows sf opp~rtunity~' in the ocean sr stream. The windows are of different widths and levels of predictability for coho and churn salmon fry and coho salmon srnolts.La variabilite de !a temperature msyenne du courant entre la p6riode maximale de fraie et Bt6rnergenee des alevins cornptait respectivement pour 82 et 77 % de [a variance de la date de migration des alevins de saurnon k6ta (Oncsrhywchus keta) et de saurnsn coho (0. kisutchj au cows d'une periode de 9 2 10 ans. Les rapports mod6iis$s 6taient indistinguables des rnod6les de laboratsire qui pr6disaiene la perisde necessaire pour que les alevins atteignent leur poids frais maximal. La variabi tit6 de la temp6rature ddu courant au printemps cornptait pour 60 % de la: variabilite de la date mediane de migration des smolts de saurnon coho. A mesure qu'augmentait la temperature, Ees somrnations therrniques prevues pour la coho, augmentaient de f a p n mod6rc5e pour les alevins de saurnon keta et augmentaient forternent pour les smolts de saurnsn coho. La duree de migration differait 6galement dfun group A B'autre : 58 % des alevins de saurnon keta rnigrent sur une peride de 1 semaine comparativernent A une p5riode de 2 3 3 sem. pour les alevins et les smolts de saurnon coho. Nous forrnul~~ns lfhypsth&se que les rapports entre le moment de la migration et la temperature et J e moment du frai A /'Age adulte representent des adaptations & une migration synchronisee en fonction de (( fenetres specifiques )) dans Ifocean s u les cours d'eau. La largeur des fenetres varie de meme que le niveau de prevision pour les alevins des saurnons coho et k6ta et les smolts de saumon coho. 'Contribution No. 140 of the @mation Creek Watershed Project. 'Present ...

Biological characteristics and population status of anadromous salmon in southeast Alaska.

“…Female body size is positively related to fecundity and competitive ability, but these characteristics do not necessarily confer enhanced reproductive success in all situations (Fleming and Gross 1989;Holtby andHealey 1986, 1990;van den Berghe and Gross 1989). Selective harvest of large males could contribute to the observed size differences.…”

“…This result may reflect the tendency for the largest male smolts, typically the oldest, to return as jacks. Female fecundity increases greatly with increasing body size, but the same relation may not hold for males; in some situations small males or jacks can have high reproductive success (Holtby andHealey 1986, 1990). Males may forage in ways that reduce their risk of mortality rather than maximize their rate of growth, resulting in a size-at-age distribution that is skewed to smaller sizes relative to females (Holtby and Healey 1990) .…”

“…Large size may provide an advantage in this competition (Hanson andSmith 1967, Quinn andFoote 1994;but see Healey 1987;Holtby andHealey 1986, 1990;Schroder 1981). The greater level of sexual dimorphism found in river-sea-type stocks suggests that sexual selection may be more intense in these stocks.…”

“…Late-running stocks often select spawning areas with relatively warm winter temperatures. The relation among spawning timing, water temperature, and emigration timing probably reflects evolutionary synchronization of these events with "windows of opportunity," such as near-shore plankton blooms, that maximize fry survival (Holtby andothers 1989, Miller andBrannon 1982). Mortality of eggs and alevins is high; only 10 percent of eggs typically survive to emergence (Hunter 1959).…”

Physiological Assessment and Behavioral Interaction of Wild and Hatchery Juvenile Salmonids : The Relationship of Fish Size and Growth to Smoltification in Spring Chinook Salmon.

“…Holtby et al (1989) showed a strong positive relation between interannual spring stream temperature and median migration timing of coho salmon smolts. Relatively higher spring stream temperatures would result in higher potential growth rates in juvenile salmonids.…”