Multiple independent indicators of American lobster in Maine: Patterns in space and time

Abstract: Effective fisheries monitoring that informs demographic trends and potential landings are necessary for sustainable fisheries management. The design of surveys to monitor a fishery depends upon data needs, management goals, and the life history characteristics of the species. The most valuable fishery in North America, the American lobster fishery, has well-developed sampling programs that include fisheries-independent and -dependent surveys. We compared six of these surveys (including diver, trap, and trawl surveys) and found positive lagged-correlation between different life stages across surveys. A decline in shallow water recruitment of early benthic phase lobsters (< 45 mm CL) precedes declines in abundance of the subsequent adolescent phase (45-83 mm CL) in the other fisheries-independent surveys since 2015. The trends in the indices of abundance varied with geography, with little change across surveys in southwestern Maine and an increase followed by decline in central and northeastern Maine. The declines in peak abundance across the surveys generally occurred earliest in the shallows and progressed to deeper water. Despite the fishery being very data-rich, lobster’s ecological characteristics, specifically behavior and habitat use, create biases due to each survey’s differences in methodology that pose challenges for interpreting underlying population scale changes from survey trends.