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Twilight had descended when the boat set out from Phillipsburg's boat launch, pulling a net 300 feet long by 12 feet deep across the Delaware River.
Biologists were gathered to catch what are known as young-of-year American shad.
American shad are anadromous fish, meaning they are born in freshwater, live for several years as adults in the ocean and return to their natal waters (where they're born) to spawn (lay their eggs) in the spring.
The young-of-the-year are juvenile shad that are born in the spring and spend their first summer in the river. As the water temperatures cool, they travel south to overwinter in the warmer waters of the Delaware Estuary and Bay before heading out to the Atlantic Ocean, where they will spend the next several years before their spawning run.
By that point, as anglers know, the full-grown shad are single-minded and aggressive, known to swing their heads at anything in their way -- including a well-placed shad dart or flutter spoon that can net a challenging sport-fish catch from the river for a few weeks each year. By bass season in mid-June, dead carcasses of the spent shad can be seen floating downriver and accumulating along the shore in spots.
With their massive seining net, the biologists were at the boat launch last Monday night for one of nine nights of young-of-year shad collections. They're done in August, September and October between Phillipsburg and Easton and at two additional locations, Delaware Water Gap and Milford in Pike County.
Together, the shad counts will be used to calculate an index for the 2019 shad run as a whole. (Additional seine hauls are done at Trenton, on the East Branch of the Delaware River and at Skinners Falls, but those locations' period of record isn't yet extensive enough to use their data.)
The young-of-year count was canceled in 2018 due to high water conditions, but the catch from 2017 was the highest in the 31-year history of the assessment that began in 1988. That's according to the Delaware River Basin Commission that organizes the survey with a Wildlife Management Cooperative comprising state and federal fisheries representatives along the river, estuary and bay.
It's too early to tell if the 2019 collection points to a poor, average or good year because it is ongoing.
"The catch was on the low side, but one night’s effort at one location may not always be indicative of the run as a whole," Basin Commission spokeswoman Kate Schmidt told lehighvalleylive.com. "While the September catch was on the low side at Phillipsburg, the catch at Phillipsburg in August was very good."
Along with shad, Monday's seining also hauled in common fish species such as smallmouth bass, redbreast sunfish, rock bass, bluegill, and various shiners and minnows.
The fish are placed in a live well and studied -- the young shad measure about 2-3 inches long -- before being released at the end of the night, said Daryl Pierce, fisheries biologist with the Pennsylvania Fish and Boat Commission.
"Eventually we can then say down the road if subsequent returns are going to be strong or poor based on this year's production," he said.
Overall, the Delaware River is known to support "a healthy run of American shad," Schmidt said:
"The catch of young-of-year shad is often correlated with the return of adult shad three to five years later, so we would hope to see good shad runs in the early 2020s."
The effort is part of the Atlantic States Marine Fisheries Commission management of American shad along the United States' East Coast. The basin commission is a liaison to the Wildlife Management Cooperative that also includes, along with Pennsylvania Fish and Boat Commission, the Delaware Division of Fish and Wildlife, New Jersey Division of Fish and Wildlife, New York State Division of Marine Resources, U.S. Fish and Wildlife Service and the National Marine Fisheries Service. Other supporting agencies include the National Park Service, Philadelphia Water Department and The Nature Conservancy.