I've fished the Porkies pretty much every year for the past 5 and have been less than bowled over.. The fishing can be good, but it is highly dependent upon adequate flows and particularly upon whether there have been any moderate to protracted spells of hot weather (by UP standards, in the mid to upper 80's and above). A lot of the streams that are ballyhooed as brook trout destinations are very small to the point that a long enough dry spell basically dewaters them and hence also detrouts them. Additionally, Porkies fish are travelers. They have to be.. Most of the streams flow over bedrock and heat up quickly and you can get on the most delicious looking piece of water and water temps can be good at the time, but if there has been a week or so of hot weather before you arrive, you'll find few if any fish. So, just be aware of that. The Little Carp, which is probably the best of the Porkies streams in terms of access to backcountry sections, water types, stream size and reputation for general quality fishing is not an exception to these influences. I've fished it 4 times in 4 different years and 3 of these times, it has been deader than Elvis. To be fair though, we've usually gone up in September and usually on the heels of a hot spell. On the other hand, the Union River, which is readily accessible just inside the eastern boundary of the Porkies, seems to hold some fish even in hot weather. It evidently has better or more frequent spring inputs than your garden variety Porkies stream. But the Union is very small in the section that reliably holds fish, from the South Boundary Road up to Union Springs. By the time you get up close to Union Spring, we're talking a stream that averages 3-5 feet in width with very little good holding water.
There are other streams, including the Big Carp and several others. But the Little Carp and the Union (along with the Little Iron just outside the park boundary) are the 3 I'm most familiar with.
Pray for wet, cool weather. You may well have a blast. But the next time I go back, I'm taking an insurance policy in the form of a 9' six weight and hiking into Lake of the Clouds for smallies.
PS: Just as an afterthought, if the fishing is flat while you are there, you aren't that far from the upper portions of a couple of the branches of the Ontonagon where the fishing holds pretty up much all season. Back towards Watersmeet, about an hour or so drive. Additionally, sections of the Presque Isle River on the western end of the Porkies have pretty good spring input and there are good numbers of brook trout available all season.
