It's always helpful if someone else somewhere else with a similar problem comes up with a suitable solution. Our American cousins famously suffered overfishing for cod in particular - here is a solution offered:
Background NE groundfish- management/monitoring
At Sea Monitors, Electronic Monitoring, Dockside Monitors
Costs, program
- What you pay
Data Quality
- What you get
http://eminformation.com/2006/2006