Trego to the fore for Somerset
Peter Trego starred with the ball as Somerset had very much the best of a rain-affected first day at Aigburth.
The 31-year-old all-rounder finished with figures of 4-34 from 18.2 overs as Lancashire struggled to 129 for five.
On a day when 44 overs were lost to torrential mid-afternoon and evening showers, Lancashire were indebted to Ashwell Prince for holding their innings together after Trego had claimed the wickets of both Stephen Moore and Paul Horton in a 10-over opening spell that cost just 12 runs.
The South African batsman made 51 off 94 balls and shared a fluent third-wicket partnership of 79 with Karl Brown, whose 39 included seven fours.
However, Trego returned in the evening session to put an end to Lancashire's limited recovery.
Brown’s off stump was uprooted when the number three played a rather loose drive and Trego completed his day's work by having Prince caught behind by Craig Kieswetter.
Sandwiched between those dismissals, Alfonso Thomas had Steven Croft caught by second slip by Marcus Trescothick for seven and the visiting bowlers ended the day in the ascendancy by giving Lancashire debutant Andrea Agathangelou a testing opening to his championship career.
The South African-born cricketer, who holds a Cypriot passport, had still to get off the mark after 20 minutes at the crease when another shower brought an early end to the day's play.
Agathangelou and Gareth Cross will resume their innings tomorrow with Lancashire hoping that their last pair of recognised batsmen can build a respectable total on a wicket where runs have proved hard to come by.
In the morning Trescothick marked his return to the Somerset side for the first time since April by winning the toss and asking Lancashire to bat in a match that saw each side give a championship debut to one of their promising young players.
Taunton-born slow left-armer Jack Leach was playing his first Division One game for Somerset while Lancashire gave a start to 22-year-old batsman Agathangelou, who also bowls leg-spin.
Both sides are seeking a win for contrasting reasons. Seventh-placed Lancashire need the points to avoid following the example of Sussex and Nottinghamshire, who were both relegated in the seasons after they won the title, while Somerset lie third and still have a chance of winning the championship for the first time in their history.