Althoug h the volume of containers handled at g lobal bellwether ports continues to increase, rate levels are s till falling . BMI fears that this overcapacity will continue over the mid term, with a news lew of mega-vesels - including Maersk Line's 18 ,000 20 -foot equivalent unit (TEU) fleet - due online from 2013. Our fear is that with 2012 set to be another year of record growth in the glob…