Oh well...one more bit...In winter conditions (which there are many variables and combination factors, Inc. Cold or Mild, water colour and level etc), the sudden rise in water temp can have a similar effect as to when it drops. After a cold snap, you have to be out there fishing at the particular temp switch on point. If the temp then carries on rising, then the barbel have to acclimatise back up...which takes time and they can/will switch off again until that happens. You can and will blank even when you think the temp and conditions seem and feel right. You can only find that out by being out there and experience, whether by logging (or memorising) temp blanks and catch temps and then sussing it out. Each winter month can have a different switch on point which generally lowers the further you go into winter, and depending on how low the water temp has fallen and which temp the barbel has acclimatised too. However I did find that the odd identified barbel were more tolerable to the cold conditions than the majority, and they were not necessarily the big ones.