I had no idea but the demise of the whaling industry in New Zealand is quite recent. Whalers were amongst the first Europeans to arrive and settle in New Zealand but I didn't realise that the last whaling station closed shortly after capturing a whale in December 1964.
This whaling station is in Fisherman's Bay in Tory Channel. You can actually see the restored remnants of this whaling station from Interislander's ferry on the crossing to the South Island. As you approach the cliffs of the South Island heading from Wellington, the ferry passes through a narrow gap then turns sharp left to sail along Tory Channel. So at this point you have the South Island on your left and another island, Arapawa Island, on your right. It's maybe just a minute or two after making that sharp left turn that the ferry passes the whaling station in a bay on Arapawa Island. You can see the wharf clearly and what is left of the processing shed there.
Apparently it was a family run whaling station and some of the family, having now hung up their harpoons, spend a bit of time checking for and counting migrating whales as they start to make a comeback in these waters. Their little observation hut is high up on the headland on your right where the ferry first passes through the narrow gap to the South Island.
Once you get off the ferry in Picton, if you're interested there's a bit of a display in the National Whale Centre in a pavilion on the foreshore in Picton opposite the Oxley Hotel