The 1995 Delaware River American shad run was monitored with hydroacoustic equipment mounted on the Interstate 202 bridge in Lambertville, NJ. Hydroacoustic equipment uses transducers underwater to emit a sound wave that counts fish as they migrate upstream.

From April I through May 9, 1995, a total of 510,000 adult shad were counted on their upstream spawning run using this underwater sound technique. The date indicates that 61 percent (309,000) of the shad passed the bridge during the month of April. The remaining 39 percent (201,000) of the shad passed the bridge in just nine days (May 1-9).

Historically, the peak of the run and thus the best fishing occurs during the month of April, as it did in 1992 when 535,000 fish were hydroacoustically counted from April 7 through May 6. In 1995, shad fishermen may have been discouraged by their low catches during this typically productive time, and may have dropped out of the fishery.

The pattern of the run for 1995 suggests that the low early spring water temperatures and the shad coming through later, en masse when the water warmed, made the timing of a fishing trip very critical to success. This late peak of the run is corroborated by the Pennsylvania Fish and Boat Commission data showing that the bulk of the shad swimming up the Lehigh River fish ladder at Easton occurred from May through early June. A creel census conducted and funded by the DRSFA (see related story) also draws similar conclusions.

In 1996, the New Jersey Division of Fish, Game and Wildlife will be using hydroacoustics at the Route 202 bridge in Lambertville during the entire months of April and May.

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