So far, my sampling has netted me lots of bluegills, both larger ones on hook and line and smaller ones with a dipnet.

I don't even seem to be seeing many other kinds of fish, which makes me wonder if I'm looking in the wrong places. I sort of expected to see small schools of minnows in shallow water of the Charles and streams that feed it, but perhaps I need to be looking in other rivers and streams. I did see a large catfish nosing around near the shore in a very algae-rich area while kayaking today, though. (that was cool.

I remember just seeing small fish/minnows all the time in the brook behind our house growing up, but that was in New Hampshire (Lakes Region), and was also ~20 years ago. It was so easy then that I'm really quite confused now.

Of course, the water I've been looking at has, for the most part, not been the clearest, which likely doesn't help at all. I wonder if I need to be finding clearer water and/or snorkling. Actually, I don't even know where might be best to snorkel in, although I may visit Walden Pond to try that out, since it does have a nice beach (rather than nasty mucky edges like the places I've been looking in lately).

I shall continue to investigate, but if anyone has pointers, they'd be welcome!

I would guess that if you went upstream a bit on the tribs that you should start running into more fish,

Snorkel everywhere. Where the water is clear. Public pools are the exception. Downstream of riffles is ideal. Lake margins and vegetation would be good locales too. If you want to catch a bunch of fish get a friend and a seine. If you only have a stout dipnet plant it downstream of you and shuffle toward it. Darters, sculpins and madtoms and assorted critters should turn up. Also push it throw vegetation and stomp things toward it.
Practice makes perfect. Come to NC and really learn quick.

Sometimes the mouths of tribs to bigger rivers are pretty silted in. So the habitat is not ideal for most fish. Often things change a great deal above the first riffle in the tributary.

What minnows are known in the Charles River watershed? It might be a short list if most of the watershed was inundated with seawater during the last period of high sea level.

From experience, the best places in the Charles and direct tribs will be areas with a sandy or gravel bottom which are relatively few until you get upstream from Watertown. Most of the Charles itself is a low gradient stream, more like a river in the south of England, with slow flow and muddy substrate. In shallow sandy areas you can hope to catch banded killifish and swamp darters; both species will be found pretty much ONLY in shallow water, which is the good news (and you might find tessellated darters, you're at the northern range limit there). Sunfish and various bullhead type catfish will be present and common; no madtoms, it ain't the southern Appalachians. Bluntnose minnows will be around in the same general habitat as the banded killifish. And Casper was right about seines, it's about 10 times easier to catch fish, maybe more.

From experience, the best places in the Charles and direct tribs will be areas with a sandy or gravel bottom which are relatively few until you get upstream from Watertown. Most of the Charles itself is a low gradient stream, more like a river in the south of England, with slow flow and muddy substrate. In shallow sandy areas you can hope to catch banded killifish and swamp darters; both species will be found pretty much ONLY in shallow water, which is the good news (and you might find tessellated darters, you're at the northern range limit there). Sunfish and various bullhead type catfish will be present and common; no madtoms, it ain't the southern Appalachians. Bluntnose minnows will be around in the same general habitat as the banded killifish. And Casper was right about seines, it's about 10 times easier to catch fish, maybe more.

Aaaah, ok. So I need to go more upstream, then.

Mostly at this point I just want to _see_ any fish other than bluegills. Catching them would also be nice, but even just seeing them would make me feel less like they don't exist.

I would guess that if you went upstream a bit on the tribs that you should start running into more fish,

Glad to know! Clearly I'm too darn close to the end of things.

Snorkel everywhere. Where the water is clear. Public pools are the exception. Downstream of riffles is ideal. Lake margins and vegetation would be good locales too. If you want to catch a bunch of fish get a friend and a seine. If you only have a stout dipnet plant it downstream of you and shuffle toward it. Darters, sculpins and madtoms and assorted critters should turn up. Also push it throw vegetation and stomp things toward it.
Practice makes perfect. Come to NC and really learn quick.

Yeah, these would be good once I find any fish. I'm currently looking for local waterholes to snorkel in, as maybe they'll be a bit clearer water.

Sometimes the mouths of tribs to bigger rivers are pretty silted in. So the habitat is not ideal for most fish. Often things change a great deal above the first riffle in the tributary.

Suddenly, everything makes more sense. Too close to the outflow!

What minnows are known in the Charles River watershed? It might be a short list if most of the watershed was inundated with seawater during the last period of high sea level.

Interesting! I hadn't thought about this aspect of things.

You hit on one of your problems - visibility/water clarity. There are lot's of fish of several species in the rivers you mention. Golden shiners in the slow parts, fallfish, common shiners and blacknose dace in the faster parts. Get polaroid sunglasses for better vis. Look for clearer tribs. Refine your netting technique - the fish are there.
Your idea to snorkel in Walden pond is a good one. I've spent many hours under the water there myself. Clarity is best in region and fish are tame from so many swimmers. Species count is very low however. Largemouth and smallmouth bass will be the stars of the show, but little else.

PS I usually agree with whatever Casper says, BUT, I don't think he's envisioning the urban setting and questionable H2O quality involved in your home waters when he advised you to snorkel "everywhere".

A minnow trap also makes a good companion to a dipnet or other collecting/sampling methods. A well placed trap that sets for an hour or so while you're sampling a few other holes can be almost like having another person along. I sample with traps weekly.

Hmm, seems I mis-spoke. According to Inland Fishes of Massachusetts, fallfish, blacknose dace and common shiners are "uncommon to rare" in eastern Ma. Guess I'm on the edge of "eastern" Ma as those are common species to me, 20 miles away, but in the Merrimack drainage.
Interesting. Maybe there's something to what Gerald said about salt water during high sea levels.