Pursuant to a recommendation of the Pacific Fishery Management Council (Council) under the Magnuson-Stevens Act, the National Marine Fisheries Service is proposing to use a new temperature index to calculate the temperature parameter of the Pacific sardine harvest guideline control rule under the Fishery Management Plan. The harvest guideline control rule, in conjunction with the overfishing limit and acceptable biological catch control rules, is used to set annual harvest levels for Pacific sardine. The temperature parameter would be calculated annually. The National Marine Fisheries Service determined that a new temperature index is more statistically sound, and this action would adopt that index.