Why does breaching a single earthen levee along a Central Valley river reconnect juvenile salmon to floodplain rice fields where they grow up to five times faster than fish stuck in the main channel?

SpaceWar —

When a bulldozer or a controlled winter flood punches a gap in an earthen levee along the Sacramento River, something that used to happen every winter starts happening again. Water spreads sideways across flat land that grew rice all summer. Sunlight hits warm, shallow pools studded with rotting rice straw. Zooplankton explode. And juvenile Chinook salmon, dropped into those flooded fields by hatchery trucks, put on weight two to five times faster than salmon of the same age stuck in the leveed main channel a few hundred metres away.

The mechanism is not mysterious. Winter-flooded rice fields support far more zooplankton — the tiny crustaceans a fry-sized salmon eats — than the adjacent Sacramento River. That is the whole story compressed into one ratio. Break the levee, sunlight reaches shallow water, decomposing rice straw feeds the base of the food web, and a fish that would otherwise starve in a fast, cold, sterile canal grows into a smolt strong enough to survive the Delta and reach the Pacific.

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