scholarly journals An Evaluation of the Influence of Stock Abundance and Global Temperature Anomaly on Pacific Salmon Body Weight in the North Pacific Ocean

2018 ◽  
1993 ◽  
Vol 50 (2) ◽  
pp. 290-295 ◽  
Author(s):  
Yukimasa Ishida ◽  
Soto-o Ito ◽  
Masahide Kaeriyama ◽  
Skip McKinnell ◽  
Kazuya Nagasawa

Changes in age composition and size of adult chum salmon (Oncorhynchus keta) from rivers in Japan, Russia, and Canada were examined based on body weight and scale measurement data collected from 1953 to 1988. A significant increase in mean age was found in Japanese and Russian stocks after 1970 when the number of Japanese chum salmon began to increase exponentially, but not in the Canadian stock. Significant decreases in mean body weight, mean scale radius, and mean width of the third-year zones of age 4 chum salmon also occurred in Japanese and Russian stocks after 1970. Based on the Japanese salmon research vessel data from 1972 to 1988, significant negative relationships between catch-per-unit-effort and mean body weight of chum salmon were observed in summer in the central North Pacific Ocean where the distribution of Japanese and Russian stocks overlaps. These results suggest that density dependence is one of the possible causes for the recent changes in age and size of chum salmon in the North Pacific Ocean.


1992 ◽  
Vol 86 (4) ◽  
pp. 792-810
Author(s):  
Marian Nash

On May 19, 1992, President George Bush transmitted to the Senate for advice and consent to ratification the Convention for the Conservation of Anadromous Stocks in the North Pacific Ocean, with Annex, signed at Moscow on February 11, 1992. An accompanying report by Secretary of State James A. Baker III, dated May 14, 1992, stated, in major part: The Convention has as its centerpiece a prohibition on high seas fishing for Pacific salmon, which will protect valuable migrating U.S.-origin salmonids. It also establishes a new international organization to promote the conservation of anadromous stocks (primarily Pacific salmon) throughout their migratory range in the high seas area of the North Pacific Ocean and its adjacent seas, as well as ecologically related species that interact with these resources, including various marine mammals, seabirds, and non-anadromous fish species. The new organization, which is to be known as the North Pacific Anadromous Fish Commission, will also serve as a needed venue for consultation and coordination of high seas fishery enforcement activities by the contracting parties.


<em>Abstract.</em>—Limits to the capacity of the North Pacific Ocean to support salmon are suggested based on widespread observations of decreasing size and increasing age of salmon at maturation during time periods where the abundance of salmon has increased throughout the North Pacific rim. The increase in abundance of salmon is partially due to successful establishment of large-scale hatchery runs of chum salmon <em>Oncorhynchus keta </em>and pink salmon <em>O. gorbuscha</em>. The largest hatchery runs are chum salmon, and because of their long life span relative to the more abundant pink salmon, the increase in hatchery terminal run biomass under-represents the actual increase in salmon biomass. To put the increase in hatchery runs in perspective, the historical (since 1925) terminal runs and biomass of hatchery and wild pink, chum, and sockeye salmon <em>O. nerka </em>in the North Pacific Ocean were reconstructed. Various data sets of smolt releases from hatcheries, wild salmon estimates of smolt out-migrants, and subsequent adult returns by age and size were assembled. Age-structured models were fit to these data sets to estimate brood-year specific rates of natural mortality, growth, and maturation. The rates were then used to reconstruct total biomass of the “smolt data” stocks. The estimated ratio of terminal runs to total biomass estimated for the “smolt data” stocks were used to expand the historical time series of terminal run biomass on a species and area basis. The present total biomass (~4 million mt) of sockeye, chum, and pink salmon in the North Pacific Ocean is at historically high levels and is ~3.4 times the low levels observed in the early1970s. At least 38% of the recent ten-year average North Pacific salmon biomass is attributed to hatchery stocks of chum and pink salmon. Recent year terminal run biomass has been greater than the peak levels observed during the mid 1930s.


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