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Electrofishing Surveys Shed Light on Dynamic Millstone River Fishery

It is June 2018 and American Shad have been on the move! Great efforts are being made to restore migratory routes of anadromous fish species (those which live in the ocean but spawn in fresh water), including river herring and American Shad. A flurry of dam removals have taken place along the Raritan, Musconetcong, and Millstone Rivers in recent years, with more on the way, including those along the Paulins Kill (i.e. Columbia Lake).

Shad fishing on the Delaware River has been hot the last few springs – in fact, even novice shad fishermen are currently catching more than a dozen per trip while wading its banks. This is not the case throughout the state, as fishing for American Shad is prohibited on all other New Jersey waters, as populations recover.

In continued efforts to restore American Shad (and other migratory fishes) by reconnecting historic migratory pathways, the Millstone River’s Weston Causeway Dam was removed during the summer of 2017 (see the DEP news release). The Weston Causeway Dam, located just downstream of the Wilhousky Street bridge in Manville, was the first impediment to fish passage on the Millstone River.

The 133-foot long and five-foot high dam was originally built to provide power at the Weston Mill. The site included a gristmill, sawmill, the dam, and associated waterpower features. The dam had no current purpose; the mill buildings were claimed by arson in July, 1983. In recent years, the dam had partially failed and was removed in August of 2017 as part of a Natural Resource Damage Assessment settlement agreement.

The Division of Fish and Wildlife (with assistance from the US Fish and Wildlife Service and the Watershed Institute(formerly Stonybrook-Millstone Watershed Association)) committed to monitor changes to the fish assemblages above and below the dam, before and after dam removal. Efforts will continue for the next several years. Electrofishing surveys are conducted during the spring and fall at five monitoring locations:

near the confluence with the Raritan River
immediately below the former Weston Causeway Dam
immediately upstream of the former Weston Causeway Dam
below the Blackwells Mills Dam
below the Griggstown Causeway

The 38-mile-long Millstone River, a tributary of the Raritan River, boasts a wide array of fish diversity with more than fifty species found in recent years. Migratory species, including American Shad, Gizzard Shad, Blueback Herring, Striped Bass, and American Eel, have been documented passing the Island Farm Weir fish ladder on the Raritan River near its confluence with the Millstone River, approximately 1.5 miles downstream of the former Weston Causeway Dam. They have also been documented in the Millstone River as part of this project. It was exciting to find adult American Shad during spring sampling and even more invigorating to document young-of-the-year fingerlings in the fall of 2016. Due to the fragile nature of these species, capture and handling are limited to minimize stress and possible mortality.

The Millstone River offers anglers a rich assortment of resident gamefish including both Largemouth and Smallmouth Bass, an abundance of panfish, and trophy-sized carp. The river is stocked annually with Northern Pike, however, those who fish it benefit from some of other nearby waterways stocked by the Hackettstown State Fish Hatchery. Channel Catfish are plentiful in the Millstone, which are presumably transplants from the neighboring annually-stocked Delaware & Raritan (D&R) Canal. Muskies are occasionally captured, possibly originating from the D&R Canal or Carnegie Lake stockings.

Transient Walleye, which are not stocked in the watershed, are likely making their way from the Delaware River via the D&R Canal. In fact, sizable Walleye (up to 6 pounds) were found in most surveys in the lower Millstone River. Stocked Rainbow Trout appear as well, coming from any number of trout stocked waters in the watershed. A rigorous fish stocking program is not necessary, as a respectable fishery currently exists, in fact additional stocking of top predators may be counterproductive to the recovering American Shad population.

In the lower reaches, the most numerous species captured were American Eel, Common Carp, Redbreast Sunfish, Bluegills, and Spottail Shiner, with moderate numbers of Largemouth and Smallmouth Bass and Channel Catfish. The surveys near Blackwells Mills and Griggstown, where the river is noticeably smaller in every measurable way, yielded large numbers of American Eel, Redbreast Sunfish, Bluegill, and native forage species such as Spottail Shiner and Tessellated Darter. Less commonly known species such as the Comely Shiner and Shield Darter (potential for listing as a Species of Special Concern) are also found in the Millstone, along with the Bridle Shiner in its tributaries, a potential State Endangered Species. Other fishes of conservation interest, and more often found in the Pinelands, are found in the southern-most headwaters including the beautiful Bluespotted Sunfish, Mud Sunfish (potential Species of Special Concern), Swamp Darter, Tadpole Madtom, and the Pirate Perch.

Although the removal of dams is considered an environmental win, negative impacts also may occur, such as expanding the range of several invasive species including Grass Carp, Flathead Catfish, Green Sunfish, and Oriental Weatherfish. Other non-desirable fishes, such as Mosquitofish and Common Carp, which have been found in the lower Millstone River, may also extend their range upstream.

By rule, anglers are actually required to humanely destroy species regulated as “Potentially Dangerous Fish” (see pages 17 and 44 in the 2018 Freshwater Fishing Digest). Unfortunately, large Grass Carp are fairly common in the lower Millstone River, with five encountered during 12 hours of electrofishing, the largest of which measured 46 inches and weighed almost 52 pounds.

Fishing access on the Millstone River is plentiful, particularly through the Delaware & Raritan Canal State Park. Most of the river is wadable or can be fished from its banks, but the best approach is drifting in a kayak, canoe or small jon boat. The river can be fished easily by boat from the primitive boat launch at the southern end of Lincoln Avenue Park, downstream of the Wilhousky Street/Weston Causeway bridge in Manville. Be sure to scope out the river in advance and plan your access and portage locations wisely as you will encounter a combination of shallow water, dams, and rapids that can endanger your outing.

With improved fish passage and the river reverting back to a more natural flow regime, one might anticipate several responses in the fish assemblage. The most beneficial change would be opening additional stream mileage to migratory species such as American Shad, Blueback Herring, and Striped Bass. Additional game species such as Walleye and Musky may also move upstream, although so may several undesirable species. As habitat shifts from lake-like to a more stream-like habitat, species such as Smallmouth Bass might outnumber Largemouth Bass. There might also be changes in Species of Conservation Concern such as Comely Shiner and Shield Darter. These are all reasons why it is important to continue to monitor the dynamic fish populations of the Millstone River.