I can only speak to part of that. They're done annually. They were designed by the science area, surprisingly enough, since catch monitoring is not really our job, but we had a lot of input into this after the moratorium came about. They're used at the assessment every year, so the fishermen record the amount of fish and the amount of gear they use, and how long it's set for, so that we can convert the information into a catch rate.
We receive close to 2,000 logbooks every year, and we come up with catch rate trends from those for different areas. We look at those and we compare the catch rate trends with trends in the sentinel fishery, which is slightly different. We also compare the trends with trends in our research vessel survey. From about the late 1990s onwards, the trends agree very well, both in direction and in spatial differences.
The logbooks are a very important part of what we look at.
I can't answer your questions about whether they're mandatory or not. Perhaps one of my colleagues can do that.