Situation: UK scallop fishing is input measures, with effort limits applied to >15m vessels only. There are no output limits. Industry members noted a decline in profits, and suggested that the effort regime was to blame. Government asked for evidence to support the claim and asked Seafish for economic analysis and evidence. Analysis: Analysis covered all vessel sizes and sea areas, for 2008 to 2016. Seafish used vessel-level annual data collected from vessel owners, combined with official government fishing statistics at trip level to identify key vessel groups, and analyse technical and business performance over a 10 year period. Findings: Key findings showed declining profits, due to declining technical catching efficiency rather than to the effort restrictions. Other key findings included: 1. Most scallops landed by UK vessels are landed by vessels that are >80% revenue-dependent on scallops. 2. Catch rates are declining all around UK. 3. Effort has been going up and landings volume going down. 4. Effort has been going up in the under 15m vessel group, which is not restricted by the effort regime (a classic boundary effect) 5. Operating profits would have fallen further if not for low fuel prices and high scallop prices. Governance: This paper will present the history, the analysis and the key textbook examples of unrestricted fishing, economic incentives and how the policy discussions accepted economic analysis of their highlighted problems."