Trawler conversion and the postwar small-boat industry

Did converting trawlers for wartime escort and anti-submarine duty cause the small-boat industry to collapse after the war?

Not immediately. Converting the vessels back to fishing use and completing their machinery created a large postwar refit workload even as new construction fell.

The prompt argues that turning fishing vessels into wartime submarine hunters could leave the small-boat industry without work once those hulls returned to civilian use. Demobilization itself generated a substantial conversion workload. Yards had to remove wartime equipment, restore fishing arrangements, and finish or replace machinery before the vessels could return to commercial service. New construction might decline, but refit and reconversion work prevented the immediate industrial collapse assumed in the question. Naval mobilization and demobilization create different kinds of shipyard demand.