The Bay of Biscay does have sailboats, (been there) but a lot of people avoid it because the weather
tends to make it a huge lee shore. The land formations funnel the wind
and waves so that they can quickly turn quite nasty. The the European surfing and windsurfing championships are often held in Biarritz (France) because of this. The Bay's west side (France) has few ports
, and those can be tricky with bars at the entrances that have shifting sands. The south side (Spain) may have more harbors, but they will be steep-to, and rocky, due to the Pyrenees arriving at the coast. Though sometimes the weather
can be nice, it is not a place for the faint of heart.
To determine the number of sailboats you could try looking for harbor statistics on numbers of slips, but that would include fishing
boats and powerboats too.