I believe they are all open 7 days a week. Here are links to All Seasons and Whitakers. Melinda doesn't have a web site, but if you are planning on going to Altmar, then stop on in.
All Seasons Sports - Salmon River New York, Lake Ontario Fishing, Fly Fishing Steelhead, Lake Ontario Fishing Supplies, Float Fishing Supplies, Fly Tying Materials, Salmon River Steelhead
Salmon River - Steelhead Fishing - Salmon Fishing - Whitaker's Sport Store And Motel
You can call Malinda's to see of she is open on Sunday.(315) 298-2993.
I think she is your best bet because she is right on the water.