(b) Spawners vs. returning 2-year-old fish relationship for the Kodiak Archipelago,
taking all streams together. The curve is a parabola, clearly much influenced by the
single large point (1989, fishers weren’t prepared to catch the available fish).
(^) (Data from Donnelly 1983, and updates in Myers 2001.)
(c) Time-series of spawner abundance for the Kodiak Archipelago. Pink salmon from
all regions have alternating strong and weak year-classes.
(^) (Data from Myers 2001.)
(d) Total Alaskan landings of pink salmon, showing rise to very high levels after the
mid-1970s.
(^) (Data from the Alaska Department of Fish and Game.)
Application of a spawner–recruit analysis as a management tool assumes in a
general way that habitat factors affecting the relationship are close to constant. That is
never true. In the case of Kodiak and other Alaskan salmon, there was a habitat
change in the 1970s that enhanced ocean survival, and thus the abundance of recruits
relative to spawners dramatically increased (Fig. 17.11c & d). Points from before and
after the “regime shift” are jumbled together in the spawner–recruit curve, making it
of questionable utility. In general, if there are enough data to define a curve, the time-