Model for Examining Early Ocean Limitation of Pacific Salmon Production

Abstract

A computer simulation model was used to examine growth and survival of all major British Columbia salmon stocks during their first 6 mo of ocean life. Factors included in the calculations were the space–time distribution of zooplankton production, timing of salmon ocean arrival and migration especially as regards overlaps between stocks, feeding and growth in relation to food availability, and mortality rates in relation to body size. It is concluded that ocean limitation of production is unlikely unless only a small fraction of total zooplankton production is available to the salmon. The model emphasizes several critical uncertainties about the marine biology of salmon: rates of replenishment of near surface zooplankton stocks (where most salmon feeding occurs) from deeper water have not been adequately measured, and the functional response of salmon to prey density is not understood. There is inadequate data on the relationship between body size and mortality rate, and migration patterns of juvenile fish have not been documented precisely enough. Hopefully some of these uncertainties will be resolved through the salmon enhancement programs. Key words: salmon, population limitation, juvenile marine production, simulation model

Wild and hatchery reproduction of pink and chum salmon and their catches in the Sakhalin-Kuril region, Russia

“…An alternative hypothesis has been advanced that suggests there is a surplus of food resources for salmon in the ocean (Shuntov and Temnykh 2004). A similar food surplus hypothesis was advanced by Walters et al (1978) in British Columbia in the 1970s that spurred the rapid development of the Salmon Enhancement Program (or SEP) in Canada. Lack of success in meeting the fishery enhancement goals of that program and a better understanding of fish foraging behavior has led Walters to refute his original hypothesis (Walters and Juanes 1993).…”

An investigation of the biological basis of return variability for sockeye salmon (Oncorhynchus nerka) from Great Central and Sproat lakes, Vancouver Island

“…(1999) reported that the growth of early migrating pink salmon was limited by the availability of pelagic prey. It is interesting to consider the match‐mismatch of sockeye migration timing and euphausiid prey availability in the context of investigations that suggested that juvenile salmonids would not be food‐limited in the sea (Walters et al. , 1978; Peterson et al.…”

Columbia River System Operation Review : Final Environmental Impact Statement, Appendix C: Anadromous Fish and Juvenile Fish Transportation.

“…The concept of "biological windows" has been developed by numerous investigators (Walters et al 1978;Bilton et a]. 1982;Boeuf and Harache 1982;Holtby et al 1989) primarily to explain the timing of smolt migration relative to coastal predators, marine productivity, and oceanographic conditions that are likely determinants of early marine survival.…”