Cycles of abundance among Fraser River sockeye salmon (Oncorhynchus nerka)

Abstract

In some but not all populations of sockeye salmon (Oncorhynchus nerka) that mature mainly at age 4, there has been a persistently "dominant" line, a "subdominant" line about 10-25% as large, and two weak lines having less than 1% as many fish as the dominant one. Suggested causes of this phenomenon that have been shown to be wrong or inadequate are the presence of a few sockeye of ages 3 and 5 in the spawning stocks and a somewhat larger rate of harvest of the nondominant lines. The only plausible type of explanation that has been suggested so far involves interaction between the dominant line and the others, and the only specific example involves a 4-year cycle of abundance of a predacious fish at Shuswap Lake, described by F.J. Ward and P.A. Larkin. Other types of interaction are possible, but have not been documented. The magnitudes of the instantaneous interaction mortality rates at Shuswap Lake are estimated as about 0.78 per generation for the subdominant line out of a 7.65 total, and 1.11 out of 7.94 for the weak line 3, line 4 being similar.Résumé : Dans certaines populations, mais non dans toutes, de saumon sockeye (Oncorhynchus nerka) dont la maturité est atteinte principalement à l'âge de 4 ans, on a observé une lignée « dominante » de manière persistante, une lignée « subdominante » qui compte environ 10-25% du nombre de poissons de la lignée dominante et deux lignées faibles comptant moins de 1%. Les causes proposées de ce phénomène que l'on a démontré erronées ou inappropriées sont la présence de quelques saumons d'âge 3 et 5 ans dans les stocks de reproducteurs, et un taux de récolte légèrement plus élevé dans les lignées non dominantes. Le seul type d'explication plausible proposé jusqu'ici fait intervenir l'interaction entre la lignée dominante et les autres, et le seul exemple spécifique fait intervenir un cycle d'abondance de 4 ans d'un poisson prédateur du lac Shuswap décrit par F.J. Ward et P.A. Larkin. D'autres types d'interactions sont possibles, mais n'ont pas été documentées. L'importance des taux instantanés de mortalité par interaction dans le lac Shuswap est estimée à environ 0,78 par génération pour la lignée subdominante sur un total de 7,65 et à 1,11 sur 7,94 pour la lignée 3 faible, la lignée 4 étant semblable.[Traduit par la Rédaction]

Resilient Salmon, Resilient Fisheries for British Columbia, Canada

“…Provided that the local habitat remains suitable, all but a few members of any population can be wiped out and the population will recover its former abundance in a few generations. A dramatic example of this capacity was shown by Fraser River sockeye salmon (O. nerka) stocks that recovered after nearly being wiped out by overfishing and a rock slide at Hell's Gate in 1913 that blocked most fish from migrating upstream (Ricker 1987). Schtickzelle and Quinn (2007) used Bristol Bay sockeye as an illustrative case to argue that groups of Pacific salmon populations are organized as a metapopulation.…”

Dynamic Complexity in Exploited Marine Ecosystems

“…Cyclic dominance refers to the disparity in population size of different "lines" of sockeye giving rise to 4-year cycles in a number of populations. Ricker (1997) reviewed potential underlying ecological and fishery-related mechanisms giving rise to this fascinating periodic pattern (Figure 10; upper panel). Myers et al (1998) showed that the interplay of harvesting and stochastic forcing can recreate basic patterns of this type for certain ranges of the parameter space and exploitation levels in a Ricker model (see Box 5).…”

The resilience of the Babine: The economic and social relations of the Babine to 1830.

“…21 Gisdaywa illustrated this point further by explaining that where the Wet'suwet'en and Babine territories met it was often the same clan that controlled the territory on either side of the line. 22 He noted that Smogelgem had nephews from Babine that would often come into Wet'suwet'en territory and trap with their uncle on his territory. 23 This combination of clearly delineated territorial boundaries and exceptionally intricate familial ties was part of a larger push-pull between the Babine and Wet'suwet'en.…”

“…This, according to Goldman, began about "150 years ago, a century before direct contact with the Whites" and allowed the "Carrier [to adopt] the social forms of their West Coast neighbours." 22 Ultimately, Goldman concluded that "effective social contact between the Alkatcho Carrier, and 20 Goldman, "Crest Prerogatives," 396. 21 Ibid., 417.…”