The website of Kim is
Whale Samana.
Last year she did tours until the end of the march.
I work with her on the boat and this season the whales arrived later so possibly stay longer but of course no guarantee on that.
We live in Las Galeras direct at the coast and can see the whales from our Restaurant. Even though last year we saw the last one mid april!, there were not much in the area in april, so more probably you will not see any after the end of march.
Today we saw a mother with a 4 week old baby and they might stay for some more weeks until the baby is strong enough to head north.
Good luck
El Cabito