How large was the Soviet submarine fleet in 1980?

Was the effective Soviet submarine total about 350 boats, excluding reserves?

Yes; Speed confirms the figure for nuclear and non-nuclear submarines outside reserve status.

Douglas Jay asks Speed to confirm a Defence Secretary's estimate of about 350 active Soviet submarines. The figure combined nuclear and non-nuclear boats but excluded reserve vessels. Speed confirms it without qualification, giving the debate a concrete measure of the force behind the broader threat assessment. Jay notes that the total exceeded four times Germany's maximum submarine strength in either world war. The comparison explains why anti-submarine warfare dominated contemporary Royal Navy planning rather than appearing as one mission among many.