Abstract
Fisheries science is concerned with the management and understanding of the raising and harvesting of fish. Fish stocks are assessed using biological and fisheries data with the goal of estimating either their total population or biomass. Stock assessment models also make it possible to predict how stocks will respond to varying levels of fishing pressure in the future. Such tools are essential with overfishing now reducing stocks and employment worldwide, with in turn many serious social, economic, and environmental implications. Increasingly, a state-space framework is being used in place of deterministic and standard parametric stock assessment models. These efforts have not only had considerable impact on fisheries management but have also advanced the supporting statistical theory and inference tools as well as the required software. An application of such techniques to the North Sea cod stock highlights what should be considered best practices for science-based fisheries management.