If you want to know about a river or stream, and you can only ask one person, best to ask an angler who fishes it regularly. Anglers will know what fish live in the river, and a good angler will know what those fish feed on. A good angler can tell you about water quality, vegetation, and the extent of annual flooding as well as how low the river gets in dry months. Best of all, an angler will know how to access the river or stream: where you can put in a boat or carry in a canoe, where you can walk along the bank or wade.

David S. Kaplan has fished every river in Middlesex County himself, and talked to experienced anglers who really know certain parts of each river. Even you you’re not an angler yourself, his book, Fishing Guide to Middlesex County Rivers, can tell you things you should know about the Assabet, the Charles, the Concord, the Merrimack, the Mystic, the Nashua, the Nissitissit, the Shawsheen, the Squannacook, and the Sudbury.

Take the Sudbury and Assabet Rivers, which I was canoeing on just a few days ago. “The Sudbury has fertile, brown water stained with tannin from decaying vegetation,” Kaplan writes. “Water transparency averages about 2 to 3 feet but varies from 1 foot over muddy bottoms after a rain to over 8 feet at the stony headwaters.” I was canoeing over muddy bottoms in the Sudbury, and could see barely a foot into the water. Turning into the Assabet from the Sudbury led to a distinct change in the water: stained more heavily with tannin, but because of the sandy bottom the water was fairly clear and I could see down as much as six feet.

I paddled up the Assabet towards Spencer Brook, and passed the outlet from Macone’s Pond. In one of his rare errors, Kaplan misspells it “Macoun’s Pond,” like the apple — Peanut Macone, who used to live next to the pond, probably would have been amused. Kaplan says this about the river at this point: “Fish-holding cover includes deadfalls, islands, a brush island, some big midstream boulders and undercut banks.” The water level was high enough that I had a hard time seeing the boulders and deadfalls, but I knew they were there, not just from years of experience but from the turbulence disturbing the surface of the water. I had to dodge several downed trees and submerged logs, and circled the one main island in the Assabet. Even though I wasn’t fishing that day, Kaplan’s 16-word description covered much of what I saw, although it missed the Kingfisher who flew within twenty feet of me, and the two kayakers beached in a backwater, and the deer fly. A little further upstream on the Assabet Kaplan describes as “lightly fished,” and indeed I didn’t see another soul although I spent a quarter of an hour pulled up to the bank of the river.

Kaplan also describes things I couldn’t see. Larry Thorlton of Billerica once caught a Northern Pike which weighed in at 18 pounds and 2 ounces. I never caught one that big, but once I did catch (and release) a big pike in the Sudbury that I knew was a solid 36 inches long because it stretched from gunwale to gunwale of my old canoe, which had a 36 inch beam. Its teeth were impressive, and you bet I used long-nosed pliers to release the hook from inside its mouth.

Worse things than ferocious Northern Pike lurk in the Sudbury’s waters:

Water chestnut infestation grows more severe every year, as in so many of our local rivers. Boaters must inspect trailers, boats, and motors to avoid spreading the nutlets of this plant and small pieces of fanwort that could introduce these virulent, exotic plants to other waters.

Water chestnut has gotten so bad that it has to be removed periodically, or it would choke out the entire ecosystem of the river.

Tragically, environmental clean-up of the Sudbury cannot boast the success of the Charles or Nashua. Toxic chemical pollutants still leach through the south bank at the infamous Nyanza site in Ashland. Despite enormous efforts to clean up this toxic mess, dangerous levels of mercury continue to contaminate the water…. The remaining 25 miles of the Sudbury suffer mercury contamination that makes their fish unfit for human consumption.

And there is not much that can be done about the toxic chemicals: the rivers may be permanently damaged.

The book is now ten years old, and has become outdated in places: for one example, when I went canoeing a few days ago I found the Town of Concord had upgraded the Lowell Road boat ramp with hard-packed stone dust, the ramp about which Kaplan writes: “During low water or when rain has softened the bank, you may need a 4WD tow vehicle to take out a trailer.”

Nor is this book any literary marvel. If you’re not an angler yourself, you won’t buy or read this book. But for those of us who are anglers, we can travel the entire length of a dozen small but remarkable rivers and streams in our imaginations; I’d rather read about the Concord and Merrimack Rivers in this book than in Thoreau’s A Week on the Concord and Merrimack Rivers.