This project is the third one in a series of projects dealing with biodiversity of fishes and benthos in the North Sea. Testing of new gears, preparation of a new electronic field guide to determine the fish and benthos species and data gathering and evaluation on a species level were the main tasks in the first two projects. This new project has six main objectives: To provide the scientific advisors to fisheries managers with the mathematical tools that would allow them to quantify the consequences to groundfish and benthic invertebrate species diversity of achieving particular fisheries objectives. To develop the ecological theory, including rigorous hypothesis testing, necessary to underpin any mathematical tool designed to enable the impact of various fisheries strategies on groundfish and benthic species diversity to be explored. To derive a detailed understanding of the spatial and temporal patterns of disruption, or disturbance, to the ecosystem caused by fishing. To determine spatial variation in benthic invertebrate productivity across the study area in each of two years. To determine spatial variation in groundfish species diversity across the study area. To determine the relationship between landings and the pattern of fishing effort needed to attain these catches.