This action implements 2010 specifications and management measures for Atlantic mackerel, squid, and butterfish (MSB). Specifically, this action maintains quotas for Atlantic mackerel (mackerel), Illex squid (Illex), Loligo squid (Loligo), and butterfish at the same levels as 2009. This action also modifies accounting procedures for underages of Trimester 1 quotas in the Loligo fishery so that Trimester 1 quota underages that are greater than 25 percent of the Trimester 1 quota will be allocated equally to Trimesters 2 and 3, and underages that are less than 25 percent of the Trimester 1 quota will be allocated to Trimester 3. Additionally, this action will increase the minimum mesh size requirement for codend covers in the Loligo fishery from 4.5 inches (11.43 cm) to 5 inches (12.7 cm). These specifications and management measures promote the utilization and conservation of the MSB resource.