Since you already found some info I'll just provide a few things I don't think are mentioned on the other thread.
Regional Fishing: Other than a few isolated populations of landlocked fish resultant of a stocking program that augments some lakes in the Greater Mat Su Valley area; salmon are found in nearly every flowing water that enters the ocean. This takes in areas ranging from the Yukon Kuskokwim River deltas in Western Ak South to the Panhandle region including the areas of Sitka, Ketchikan, and Juneau. The various species also occur off shore entering the river systems on nearly every island in the territory. I live in South Central AK and here our fish spend their time at sea in the Cook Inlet which is a huge body of water that connects to the Gulf of AK via the Kennedy Entrance. As for addressing the best regions for fishing salmon that would be a matter of conjecture if I were to state one as being superior to the others. Certain places do however experience locally heavy runs of a species such as the incredible Pink salmon runs in the Prince William Sound waters. In South Central the Kenai River consistently provides the most substantial runs of King salmon and also accounts for the state record fish. Kenai fish (kings) average 30 or more pounds and that water shed is revered as being a producer of the big boys.
What is different about AK vs. the Great Lakes tributaries?
Alaska is fortunate in that there are few areas that have an introduced population of salmon per a stocking program. Nearly every fish caught is a wild fish that has evolved from pure anadromous genetic strains. Although some species such as Sockeye have a reputation for not being susceptible to the fly; interestingly anglers manage to take many thousands on the fly annually. My own experience with Sockeye (Reds) is that out of every ten fish I encounter one in ten will aggressively take a fly.
As for king, chum and silver salmon, they are truly ready to hit darn near anything that you get near them. This statement does come with a caveat; this being that if the fish are under an inordinate level of fishing pressure from a visible human being they tend to get lockjaw and will not even look at a fly, avoiding them and scurrying away to safety.
For example; I fish for silver salmon often using a Whitlock Sculpin in a size 4 6X long. The fish respond with gusto to the presence of this prey form leading me to conclude that they readily take flies. Likewise, king salmon seem to love my Bunny Fur Comet and when I locate a pod of kings having multiple fish hooked prior to finally landing one is common; again leading to a conclusion that they readily take the fly. Chums, although sporadic in my rivers also are very cooperative. Pinks are easily coaxed to the fly and can provide a great days fishing along with some really good canned or smoked fish. The one thing that I do not show the fish is me! This is the single best advice I can offer regardless of where you fish for salmon.
It should be noted that the nearer you are to the salt water, the more likely the fish will be attentive to your fly casting. As they travel farther into their natal watersheds they become increasingly wary of humans and more focused on the job at hand.
In summation; I find the fish much more suitable game for the fly rod than those in the Great Lakes fisheries. Here the thought of presenting a small nymph like fly on a light leader would be an exercise in futility. The fish are seldom leader shy and when it comes to a fly, the bigger , the better. Steelhead are of course another story and will be addressed it due time.
I hope this read smoothly and will lend some clarity to my experiences here. If there are further questions I will attempt to address them.
Here's another remedial question for you (something that I should probably look up on my own). If Sockeye are "reds", then what are "silvers" and "pinks"?
Sounds like I would need to leave my 6 wt., 5x tippet, egg patterns behind they (work well on the Ontario tribs) if I were to fish for Salmon in Alaska.
The point about not showing yourself works well for fishing most species and, frankly, is one of the best reasons in my opinion, for being able to cast long; and the idea of getting them close to the ocean; before they stop eating and starting thinking "next generation", is a good one.
Everyone has their own specific preference for hooking, fighting, and landing a salmon. I began to fish for salmon in 1980 and in that first year was fortunate enough to hook, play, and land several Salmon in coastal Maine. Once while struggling with a fish in the 10lb class an older gentleman was kind enough to attempt netting it for me. Each time the fish was near enough for him to thrust his net after it the fish would bolt and I would allow another line ripping, scorching run. When we finally managed to get the fish into the net the gentleman looked at my leader as it protruded from the fishes jaw and ask; "What the H*** are you using for a leader man!" I told him 5 pound tippet and then he literally bellowed at me " For God's sake man, what are you thinking? You're fishing for a fish that can run 20 pounds! Are you here to catch em or torture them eh?"
This incident made a lasting impression on me and I have never under lined myself when fishing for salmon since. I seldom fix a leader to my line under 20 pound test. Some days salmon are so hard to find that after hiking and fishing for hours on end it would be unforgivable to locate fish only to have them break off from an 8 pound leader.
For kings I use 25 pound leader and in many instances I am under lined. The choice of leader for kings presents a special conundrum. Unless your backing is 80 pound test the leader best be lighter than the backing. I use 36 pound backing so the 25 pound leader gives me an 11 pound margin of error before a Kenai King heads down river with my SA Mastery DT 9 in tow.
My style of hooking and landing a salmon (any species) is all about getting the fish on the beach. If I can do so without the fish making a single run I have done an outstanding job of catching a salmon. There is no need for using a light leader and thus allowing the fish to make run after run based on the argument that you can't stop them. Even with a heavy line the runs will occur on their own. Some fish just plain take off and you can not turn them. In this scenario having a heavy leader will help you to avoid the demeaning and often dangerous run down the shoreline. You will pressure and turn the fish, maybe just not as quickly as you would like. I should add that this does sometimes require that you follow the fish rapidly in the direction of the run in order to attain a position perpendicular to it so that you can exert the side pressure needed to turn it.
About not showing yourself to the fish:
This does not always mean a double haul cast. 90% of the salmon I catch are within 20 - 25 feet of my position. I maintain a low profile while searching for fish. After locating fish I move very slowly and do my best to look innate. Cryptic clothing is a must, (no bright colors) and precise casting allowing for the proper depth and drift to be attained at the target is a must. In short there is more to consistent success than meets the eye.
We can expand on the topic of accuracy in relationship to the difference between where you cast and where you want to present. However, I believe many of us understand this principle; if not, by all means ask and I will do my level best to make clear my meaning.
I think Ard has covered all of the Salmon but I will add a bit.
Alaska has all five of the Pacific Salmon, Kings (Chinook), Silver (Coho), Chum (Dog), Pink and Red salmon. Some information indicates Salmon don't feed after they enter fresh water. They do pick up roe but some think they do it to protect it and not to eat it. I think most Salmon are caught due to a reactionary strike rather than feeding.
A friend who ran a lodge on the Kvichak River told me a trick for catching Red Salmon. They are the least likely to take a fly. The Kvichak has millions of Reds every year and he had a chance to try just about everything. He suggest that instead of putting the fly on its nose like we do with most fish, try this. Present the fly so it goes under the fish from one side to the other close to the eye. So the fish is sitting in relative shallow water and the fly comes from one side of the fish, right behind the nose, and comes out on the other side of the head. He swears that the fish can't stand it and will grab the fly as it comes out on the other side of its head. I never had the opportunity to try it on reds. I have caught Silvers in shallow water when I could observe the take and they always took a fly that was fished under it and out the other side of its head. They take just about any presented fly so I don't know if it was a good test.
Alaska Salmon have different times of the year that a specific spices will return to a river. There are peak times of the year that a river will have the most of one type of Salmon. It is true that at certain times more than one type of Salmon are present. Fishing the Kenia River for Silvers early in the Silver season you are just as apt to catch Pinks that are just ending there run.
Anyone who is planning a trip to Alaska should select their target fish, the just got to have fish, and then plan your trip around the dates that fit that fish. To make things more complicated each river will have different dates according to where the river is located.
In many areas rainbows are closed until June 15. These are spring spawners. You must check the regulations carefully because other waters are open prior to June 15. For the sake of an answer I would say June will assure open fishing through out the state and for a target species like this the Iliamna area and Bristol Bay watersheds would offer the best fishing.
With a little luck AK Guide will see this and add more clarity to this issue.
In as much as Dave had been asking about the Alagnak in another thread I'll assume that is still the water of choice for this question as there are to many different areas in Alaska with different closure dates for bows. And on the Alagnak targeting rainbows is always a good idea, the river opens to rainbow trout fishing June 8th and if you can be there then it is a blast, that said the river usually offers good to excellent rainbow action from ice out to freeze-up.