Since this thread is all about fishing and algae, I'll post my question here instead of creating another thread.

I started a new game of VV2 a couple of days ago. (I had played it for the first time a couple of months ago, but I stopped when I had developed level 2 of every technology and solved about 40% of the puzzles, so please don't post any spoilers.) Difficulty was set to "easy". I remembered that it's vital to build the dam early in the game in order to prevent my villagers from starving. It was completed before the algae showed up, and the villagers completely focused on planting and harvesting crops instead of fishing. Now that I have solved about 6-7 of the riddles, the ocean is still crystal clear. But I know that it is necessary for the algae to show up because one of the later riddles is to get rid of them. Did I mess up the game because of switching to farming too early? I tried to make the villagers fish again, but they just seem to prefer planting crops. I had to manually place them in the ocean every time as they just wouldn't keep fishing.

What can I do to make the algae show up? And why do the villagers refuse to fish? Any help would be greatly appreciated.