Yanking fish off the beds has an impact. How meaningful depends on the circumstances. Marginal waters (i.e. low spawning habitat, highly variable water levels, etc) will show bed fishing having a greater impact. Species differences abound too. For example smallmouth bass have been shown to be more aggressive on the bed, and additionally less likely to return to the bed after being captured than largemouth. Due to smallmouth colder water temperature preference, eggs typically take longer to hatch, allowing more eggs to be consumed by predators, especially once they vacate a bed.
I, long ago, made the ethical decision to not fish for spawning bass in rivers and other marginal habitats and encourage others to do so. In large bodies of water, with healthy populations, knock yourself out, but it is not for me. PS I find it interesting when one is an ardent catch and release fisherman (for the species stake) yet practices heavy bed fishing (which doesn't allow those genes to be passed down as easily).
