One thing you can probably count on is that the fishing will be insane. The problem is you won’t know whether it will be insane good, or insane bad. September will be chinook salmon time, and the river is likely to be very crowded. You may not have a lot of room on most sections, and will be sharing a pool with 300 of your closest friends. If you can, try and go during the week, but even then it is likely to be crowded.
There is the possibility of insane good fishing too. The fish are HUGE, and there are lots of them. Spectacular fights and strong fish, and there is a chance of Coho (silvers), browns and perhaps a few steelhead starting to trickle in during September.
The river is dam controlled so flows can change from day to day, and in some cases can be down right dangerous. A wading staff and strap on cleats (Korkers) are highly recommended for safety. This is a very strong river with very slippery rocks, and if you hook one of these beasts you’ll often have to chase it.
Don’t know what weight rods you have, but chinook salmon are big fish, so a 10 weight if you had it, would be ideal. I don’t think I’d want to go lower than 8 and even that is iffy. If you were going later , mid-late October and later it would be mostly steelhead, with the possibility of browns and perhaps coho and 7,8, or 9 would be fine, with most people using a 7 or 8 weight. A 9 or 10 foot rod would be ideal assuming you’d be using a single hander for controlling line on the water. Spey rods are gaining in popularity up there too.
Here’s link to the NYS DEC where you can get maps of the river. Lot’s of public access and 2 FF only areas where you might find a little more room. Make sure you are familiar with the regs, there are special ones in effect on the Salmon River and other tribs.
Fishing The Salmon River - NYS Dept. of Environmental Conservation
Here’s a link to the Douglaston Salmon Run. The DSR controls access to a portion of the lower river, and charges to fish there. They also limit the number of people, so it’s one way to get a way from the crowds. The site also has river reports so you can check flows and catch reports.
Douglaston Salmon Run, World-Class Salmon Fishing<<>>
Finally, if you’re new to this kind of fishing I would highly recommend you spend a day with Loren Williams, or if he’s booked, a guide he recommends. (There are a lot of slime balls that are “guides” up there.) Your chances of catching a fish will go up exponentially, you may get access to better stretches of water (other tribs) but most importantly you’ll get a great lesson in reading water to know where salmon are likely to be (that can change dramatically depending on river flows), and in the specialized techniques and different rigging methods used to catch these fish. If you book a day with Loren at the beginning of the trip you’ll be able to apply what you’ve learned for the rest of the time you’re up there, as well as on future trips. Here’s his site (it has a ton of good info on it)
Traditional Fly Fishing Guide Salmon River-Pulaski and Syracuse areas of New York: Salmon/Steelhead/Inland Trout guiding photos articles
It’s an exceptional fishery in an economically depressed area, crowds can be unruly at times and unethical (snagging and lining fish), there are fist fights over pieces of water, etc at some times, but very courteous and respectful at others—yielding to fish on, helping you land fish, and enjoying in the success of others etc. Bring a good sense of humor. There’s lots of lodging in the area, but it will start filling up fairly soon for prime salmon season.
After salmon season the crowds start to peter out, and the steelheading starts.
Keep asking questions as they come up, lots of folks on the board have been up there. Good luck!