North Pacific Anadromous Fish Commission

Technical Report 11

Table of Contents

Validity of Inferring Size-selective Mortality in Pacific Salmon from Scale Circulus Spacing

Authors:
Terry D. Beacham, H. Andres Araujo, Strahan Tucker, and Marc Trudel

Abstract Excerpt:
Beamish and Mahnken (2001) proposed that most natural mortality of Pacific salmon during the marine life history phase was size-dependent and occurs in two major episodes. The first phase of mortality was suggested to be predation based and occurs after the smolts enter the ocean, with other studies on salmonids typically reporting relatively high mortality after initial ocean entry (Parker 1968, Hartt 1980). The second phase of mortality was suggested to occur in the fall and winter of the first year in the ocean, when those individuals that have not attained a critical size die because they are unable to meet minimum metabolic requirements (Beamish and Mahnken 2001). Beamish et al. (2004) indicated that Pacific salmon had to achieve a sufficient size by the end of the first marine summer to be able to survive the metabolic demands during a period of energy deficit in the late fall and winter.

DOI:
https://doi.org/10.23849/npafctr11/56.58

Citation

Beacham, T.D., H.A. Araujo, S. Tucker, and M. Trudel.  2018.  Validity of inferring size-selective mortality in Pacific salmon from scale circulus spacing.  N. Pac. Anadr. Fish Comm. Tech. Rep. 11: 56–58.  https://doi.org/10.23849/npafctr11/56.58