I do not know when sawbellies (aka alewife herring) first became a food source for brown trout in the DEP’s Catskill reservoirs, but it has been a very long time. For example, I recall visiting the Pepacton Reservoir at Cat Hollow, not far from Downsville, in the late 1950s. We drove to Pepacton, because we heard that large browns were being caught from shore in the evening and early morning with a variety of lures.

I remember two things about that trip: we didn’t catch any trout, and I fell asleep on the bank.

Sawbellies are members of the herring family and, as such, are ocean fish that migrate into freshwater streams to spawn during the spring, normally the month of May. The ocean variety averages about 12 inches in length, while those that live in large lakes and reservoirs seldom exceed six inches in length. The perfect size for trout food!

How sawbellies got into Catskill reservoirs is a mystery of sorts, because there is no history of the state stocking them as a food source for brown trout and smallmouth bass. A good guess is that some enterprising sport fishermen learned that a diet of sawbellies would grow brown trout to a large size very quickly, purchased some sawbellies from a bait shop, and released them into the reservoirs.

I think Pepacton was the first, with Rondout, Cannonsville, Ashokan and Neversink to follow.

Prior to the introduction of sawbellies, brown trout and smallmouth bass that inhabited those reservoirs fed on a variety of native minnows and very small panfish. Not the best forage to promote favorable growth. For example, a 20-inch reservoir brown trout that feeds on a diet of minnows and small panfish will weigh perhaps three-and-a-half pounds. In contrast, a brown trout of the same size that feeds on a steady diet of sawbellies will weigh right around five pounds. I know that to be a fact, because the only brown that I ever caught from the Pepacton Reservoir measured exactly 20 inches and weighed right at five pounds.

Why such a difference in weight in browns that feed on sawbellies, when compared to trout that feed on small pan fish and minnows? There are a couple of reasons. By the time panfish spawn, the eggs hatch and the young-of-year are large enough to eat, inshore waters are way too warm for brown trout to feed in. Sawbellies are plankton feeders and use the abundant supply of those small organisms to grow rapidly.

Most importantly, sawbellies inhabit the same temperature zone in reservoirs that brown trout do, which is right at the 60-degree Fahrenheit level. Depending on the time of year and once waters begin to warm in spring, that temperature can be right at the surface in May or down 50 feet in August.

Getting back to the one brown that I caught in the Pepacton Reservoir: That fish was hooked using a live sawbelly for bait, with a small float, fishing five feet below the surface. Later that same year, my friend Tony and I found the 60-degree Fahrenheit level to be 35 feet below the surface, using an electric thermometer with a long probe. We caught several nice smallmouth bass fishing at that depth with live sawbellies and bobbers, to maintain that level. Tony also caught a nice five-pound brown.

Because sawbellies are so abundant and inhabit the same temperature zone as brown trout, the trout grow very rapidly and obtain a large size because of the food supply. Fish of 10 pounds are not uncommon.

Now that it has been established that the introduction of sawbellies has positively impacted reservoir brown trout fisheries, what does that mean for fly fishers? Every fall, beginning sometime in October, sexually mature brown trout begin their annual spawning migrations from every one of the DEP’s Catskill reservoirs. Those trout swim up the East and West Branches of the Delaware, the Rondout and Neversink Rivers and the Esopus Creek, on their way to the tributaries where they mate and spawn. And since the DEC extended the season from October 1 to March 31 of the next year, anglers can fish for these large spawners with a fly rod, even though all trout taken must be released.

In addition, and as a result of the annual spawning process, a new-year class of young trout is added to the fishery of both the tributaries and reservoirs annually.

So whether you are a reservoir or river angler, the introduction of sawbellies into the DEP’s Catskill reservoir system has had a very positive impact on the region’s trout fisheries and trout fishing. Where else can anglers find trout up to 10 pounds, in so many waters, on a year-round basis, within 100 miles of Manhattan? All because of the introduction of one little fish!