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Shad of the Raritan River

By Jaime Darrow and Brian Neilan, Seasonal Fisheries Technicians


An important resource

The American Shad, Alosa sapidissima, was once one of the most plentiful, anadromous fishes to swim up the Raritan River. Like other anadromous fishes such as the smaller river herring, and the popular striped bass, American shad spend the majority of their lives living and growing in the ocean. They return to their natal rivers to spawn when water temperatures warm and the shadbush begins to bloom.

The Raritan River is the largest watershed completely within New Jersey that supports migratory fish species. The shad run in the Raritan had previously served as an extremely important commercial fishery in the region, contributing greatly to the local economy until their numbers began to plummet by the end of World War I. The increased industrialization of the region resulted in severe pollution and the construction of dams which left the Raritan unsuitable and not navigable for shad, cutting them off from their spawning grounds. These problems, combined with commercial overharvesting, reduced shad numbers to almost zero, robbing the Raritan of one of its most vital environmental and commercial resources.

Damn the dams

The Clean Water Act plus a renewed commitment to the state’s environmental resources in the 1950’s brought new life to the river as water quality greatly improved. These improvements resulted in shad once again returning to the banks of the “ol’ Raritan.” Unfortunately for American Shad, their journey up the Raritan River was still nothing short of challenging. Dams, mostly stone remnants of eras gone by, continued to impede their movements upstream. In the realm of dams, the dams of the Raritan are considered low head. However considering the relative shallowness of the Raritan River these dams pose significant blockages, not only to anadromous species but to resident species as well . Critical stream connectivity is severed resulting in sedimentation, elevated temperatures and destruction of fluvial habitats. In 1983, the Division of Fish and Wildlife began addressing the issues of the dams by breaching (partially removing) the lowermost dam on the Raritan, the Fieldsville dam, as part of a federally funded restoration project for the river. That was a start.

One shad, two shad, three….

The removal of the Fieldsville dam opened three more miles of river to returning shad. Improvements to water quality continued. New Jersey’s growing population, however, resulted in increased demands for water resulting in the replacement of a small dam located near the Millstone confluence, with a much larger one, the Island Farm Weir was constructed in 1995. Current regulations require dams constructed on known migratory fish pathways to provide for fish passage. So the Island Farm Weir, constructed by the New Jersey Water Supply Authority, working in cooperation with Fish and Wildlife, included a large vertical slot fish ladder, complete with a 3-foot wide, 5-foot high viewing window. For a four foot high dam, the Island Farm Weir ladder is quite large, comprised of eight rooms measuring 12 x 35 feet, each separated from the room before by an eleven inch wide slot. There is only a 6-inch differential of water height from one room to the next.


In an effort to better understand the number of American shad still using the Raritan River as spawning grounds, the Division of Fish and Wildlife began an ambitious project at the Island Farm Weir fish ladder in 1996, monitoring the passage of fish utilizing the ladder. American shad, and the river are not conducive to traditional sampling methods such as electrofishing, and gill nets. From the beginning of April through the end of June, from 1996 to 2003, remote access video equipment recorded the passage of fish through the ladder as they passed by the viewing window. It was the job of Division employees to maintain the ladder, keeping it obstruction free and retrieving the videos for viewing at the Lebanon Fisheries Laboratory. As there is no electricity to the viewing room, that is located below the river’s flood stage, batteries that power the system have to be changed three times each week. These videos were then reviewed at the Lebanon Fisheries Laboratory for the purposes of fish enumeration and identification, with American shad being the targeted fish species. In the first year Fish and Wildlife was able to record the movement of American Shad up the Raritan River, they were surprised to find that 49 American Shad made the journey upstream of the Island Farm weir. “We were only anticipating one or two shad, and to see there were 49 really gave us hope for the future,” remarked Lisa Barno the Chief of State’s Bureau of Freshwater Fisheries. 2,740 fish were documented using the ladder that first year, representing 20 different species. The years immediately following, provided some initial optimism with numbers slowly increasing each year, with the height of passage occurring in 2001 with 592 shad, and over 6,000 fish documented using the ladder. Fish passage monitoring in 2003, and 2005 noted a disturbing decline, with 364 and 22 shad, respectively.

The declining numbers are consistent with the decline of American shad seen up and down the east coast. The lack of data to demonstrate a sustainable fishery in the Raritan will no doubt result in a closure of the fishery in 2013 in accordance with the Atlantic States Marine Fisheries Commission Shad and River Herring Plan.

Fish passage at the Island Farm Weir is affected not only by the number of shad in the river but also by the ability of fish to navigate the Calco dam, located a mile downstream. After the breaching of the Fieldsville dam, the Calco dam became the lowermost impediment to fish passage on the Raritan. Through the efforts of the Delaware River Shad Fishermen’s Association, the Calco Dam, a notch was cut in the concrete dam face to permit for passage of fish through the dam. Fish passage through the Calco notch, however, is only effective during higher flows of 800 cfs or more. Consistent low spring time flows no doubt prevented shad from getting above the dam.

Efforts Continue

Over the past few years NJDEP has worked diligently to remove three dams on the Raritan River, including the Calco dam, the Nevius Street dam, and the Robert Street dam. The removal of these barriers would open up a 10 mile stretch of the Raritan River for American Shad and other fish species to utilize. NJDEP’s Natural Resource Damages Program negotiated removal of the three dams as part of a settlement agreement with the El Paso Corporation.


On July 19, 2011 the removal of the Calco dam began. Today, the Raritan River flows freely from the Island Farm weir and fish ladder, all the way to the Raritan Bay. A total of 6.1 miles of unobstructed river is now available for fish to move through. The Island Farm fish ladder is their next challenge. After they navigate the fish ladder, they are then headed for the Nevius Street dam. During higher water flows, the Nevius Street dam is passable by fish, allowing them to travel upstream to the Robert Street dam. In July of 2012 the removal of the Roberts Street dam was completed. This elimination cleared the way for fish to access another two miles of waterway for possible breeding grounds on the Raritan River. The removal of Nevius Street dam is anticipated sometime in 2013.

p10-Fish-ladder-design_opt.jpgAs a result of these removals monitoring of shad passage at the Island Farm Weir was resumed for 2011, and 2012 to collect current information on the status of the shad.

The removed and breached dams will increase the quality of the water and surrounding habitat. Water quality will become more favorable for native species and will facilitate the eradication of undesirable species that were once favored by the pooling effects of dams. Native species will be able to disperse throughout the water body and aid in increasing the biodiversity upstream and downstream of the previous obstructions. Fish and other species will also be able to re-establish their gene flow between individuals that were once isolated. Sediment will be able to travel downstream in the currents, preventing geomorphic impacts, like the widening of streams. The removal of these dams, in the Raritan River, will help New Jersey restore the ecological functions of a free-flowing river and will show the beneficial effects over time.

The future of the shad in the Raritan

Final-Shad-Photo_Crop_opt.jpgUnfortunately, the Raritan River American shad still face an uphill battle as their stocks are extremely low due to many decades of pollution, river impounding dams and commercial overfishing. There may be a light at the end of the tunnel for shad though, as conditions on the Raritan River have greatly improved over the years with the passing of State and Federal Acts aimed at reducing industrial pollution. Also in the shad’s favor, is the push for the removal of dams and other impoundments on the upper stretches of the Raritan. The removals of the Calco and Robert Street dams as well as the planned removal of the Nevius Street dam are excellent steps toward rebuilding the American shad run of the Raritan River. Such measures have been shown to restore anadromous fish runs in other rivers throughout the country.


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