It is established for the late 20th century that sediment scale counts from the Santa
Barbara Basin are reasonably well correlated with fishery estimates of the regional
anchovy and sardine stocks. Most of the scales in the sediment are from fish less than
2 years old, those with highest mortality rates. There is no evidence of scale
deterioration or loss from the sediments, in fact counts decrease over the 2000-year
series as a whole. Anchovy are generally the dominant fish, two to three times more
abundant on average over two millennia. Both species come and go in quasi-periodic
fashion, anchovy with more obvious regularity than sardines. Spectral analysis shows
a dominant period for anchovy of about 100 years, and for sardines of about 160
years. The spectra show some shorter period “energy” as well, but that isn’t obvious
in the raw series. Both of these periods are longer than the few cycles of variation
apparent in fishery results, suggesting that the system has been changed by some
combination of industrial-scale fishing and recent shifts in the basic character of the
habitat. In any case, the sediments establish that regime shifts have always existed; we
ff
(ff)
#1