The ports of Los Angeles and Long Beach have again moved the start date of a fee that would charge ocean carriers for lingering cargo containers. The start date is now planned for April 15, but implementation will depend on the weekly progress of how many older imports are staying on the ports’ docks past their allotted time. So far, leaders from both ports have been seeing the number of aging containers fall by 49% since first announcing the fee Oct. 25. Recently, Pacific Merchant Shipping Association reported better dwell times for cargo leaving by truck in February, with an…