When using a Thunderline / Dyneema mainline it is a good idea to use a short length of clear monofilament as a leader on the end.
When bottom fishing for Whitefish or Squid the monofilament leader acts as a weaker link that will break before the mainline. It is also much easier to handle while lifting fish aboard the boat.
When jigging for Mackerel, the last few metres of the mainline take the most wear from the rollers and stripper box so the leader helps preserve the Dyneema line.