Well we can rule out progressing to another tech level because i didn't spend any teck points at all, in stead i waited for the algae to arrive before buying the next level in any of the advancements.

I think the algae comes after you've been fiishing for so long, perhaps the only way to test that out will be to fish then stop till you need to fish again and keep doing that and see how many game year's go by, i managed four years with three villages constantly fishing.