The lower Delaware was an open sewer at the height of World War II. Along some reaches, the pollution robbed the river of all its oxygen, making it impossible for shad and other fish to breathe.
The American shad that hatched in the Delaware and migrated to the ocean to spend most of their lives tried to return to the river of their birth to spawn after reaching adulthood. Unfortunately, the "pollution block" in the Wilmington/Philadelphia/Camden vicinity -- areas where there was not enough oxygen in the water for them to survive -- severely interfered with the spawning run. The Lewis fishery in Lambertville, New Jersey caught 10,000 shad in 1896. By 1953, the total catch was zero.
A major goal during the 1960s and 1970s was to bring the river back to life.
Today, the cleanup of the Delaware is hailed as one of the world's top water quality success stories. The number of American shad in the Delaware River has increased dramatically due in large part to pollution control programs conducted by the Delaware River Basin Commission (DRBC) and other environmental agencies.
The data in the chart below were generated from sampling on the Delaware River off Philadelphia during the summer months. It shows that dissolved oxygen (DO) levels have been increasing since 1965, while fecal coliform concentrations have dropped. High levels of fecal coliform indicate the possible presence of harmful bacteria in a water body. When there are too many bacteria in the water, they may overpopulate and use DO in great amounts.
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