Dave Broom, in his article on Springbank distillery in issue 19, raises the question of whether the stories of the Campbeltown distilleries using herring barrels in the early 20th century were really true or not.
I don't have the definite answer, but I did stumble across something that might just throw a bit more light on this.
From Kenneth Kilby's book on coopers and coopering ("The Cooper and his Trade"), it is clear that there were several types of coopers. Dry coopers made barrels meant for containing non-liquid goods, wet coopers made barrels for holding liquids. The latter type of cooper was considered a 'higher' craftsman and the barrels were of course made to higher specifications as they shouldn't leak, etc.
Coopers making barrels for the fishing industry were called dry-tight coopers and their barrels were the highest quality among dry barrels. Typically, herring barrels were made from spruce and/or fir wood.
First of all, I wonder if the typical spruce/fir herring barrels were tight enough to hold maturing spirit for any length of time. If they WERE, whisky in it would have matured in spruce/fir wood .... that could have given the whisky a very odd taste, given the resins in those kinds of wood (think of the Greek retsina wines!).
So, after reading more about herring barrels, I think it is quite unlikely that they were ever used for maturing whisky at any scale. But if it DID happen, the whisky from it will have been even stranger than I originally thought!