Why naval guns did not use tank-style spotting rifles

Before radar ranging, did navies consider subcalibre spotting rifles like those used by tanks?

Not in a practical way. Naval ranges and ballistic requirements made salvo-based ranging a better solution.

A useful spotting weapon would need to reproduce the main armament's long-range ballistics closely enough that it would cease to be truly small. Naval combat ranges therefore made a tank-style spotting rifle a poor guide to where a heavy shell would fall. Instead, gunnery officers used structured salvos, often groups of three rounds, to observe the pattern around the target and refine the range solution. Multiple turrets could alternate those small ranging salvos before the ship committed the full battery.