CBS Evening News | Thousands of dead fish, stingrays, crabs and shrimp have washed ashore on Gulf

Thousands of dead fish, stingrays, crabs and shrimp have washed ashore on Gulf beaches due to a lack of oxygen in the Gulf of Mexico from the so-called "dead zone." It appears every summer, but this year's is more than twice the size of last year's. Chip Reid reports. Air Date: Jul 30, 2013