Recruitment of Pacific sardines is highly variable and indications show little resilience to fishing. Recruitment occurs in strings, with several years of good recruitment followed by similar periods of poor recruitment. The timing and duration of these strings has a large effect on population growth. The spawning biomass of Pacific sardine averaged over three million tons in the early 1930's, decreased to less then 100,000 tons in the early 60's. The spawning biomass in 1990 was estimated to be 130,000 tons.
Many researcher now feel it has been a combination of several factors.
With good environmental conditions and lack of fishing, the sardine population is beginning to recover. Harvest Pacific sardines were harvested with purse seines and supported the largest fishery in the western hemisphere in the 1930's and 40's with peak catches of over 700,000 tons. The fishery then collapsed to less than 1,000 tons in the 1960's. They are regulated as an ocean food fish. The plan is presently not in effect, but as of their August 1994 meeting, the Council is considering completing the draft plan in the near future.