The Quinnipiac River is the fourth largest river in Connecticut, and yet very little data exists regarding the diadromous fishes in that river. This limited knowledge has made it difficult for environmental managers to effectively manage the river's resources. Migration of anadromous species is currently blocked by the first dam on the river, the Wallace Dam, located a short distance downstream of the Route 150 bridge in Wallingford (river kilometer 20). Scientists belive that if the dam is made passable, anadromous fish will enjoy greater spawning success in the less crowded and less impacted mid reaches of the Quinnipiac River. The Quinnipiac River is a good candidate for such a restoration because of the documented existence of an anadromous fishery (mainly Alosa spp.) dating back over 200 years. There is abundant habitat above the dam so that anadromous fish could move upstream and take advantage of it if they could first get above the dam.

The objective of this study was to survey the diadromous fishes of the Quinnipiac in order to better inform managers about the fish resources in the river. This knowledge will help in making management decisions concerning a Wallace Dam fish passage and whether or not a chemical barrier to fish exists at any permitted discharge. To these ends seven sample sites were established in the lower Quinnipiac, all below Wallace Dam. A diverse array of sampling gear was used to capture fishes including basket traps, hoop nets, dip nets, and seines. The gear was placed in the river from 25 April to 4 July 1997, and most sites provided continuous sampling of the river.

Twenty-four species were collected during the study, eight diadromous (seven anadromous and one catadromous species) and 17 freshwater species. Nine diadromous species were targeted for this study, as we expected to capture them due to the coincidental timing of this study and their spawning migration. Eight out of nine targeted species were collected (alewife, Alosa pseudoharengus; American shad, A. sapidissima; blueback herring, A. aestivalis; American eel, Anguilla rostrata; gizzard shad, Dorosoma cepedianum; striped bass, Morone sexatilis; white perch, Morone americana; and brown trout, Salmo trutta). The only target species not collected was sea lamprey (Petromyzon marinus).

Both diadromous and freshwater fishes were captured during the study, numbering 1197 and 637 respectively, for a total of 1834 fishes. All target species were collected at upper sites (sites 4, 5, 6, and 7) indicating the abscence of an absolute block in the river to those species. Compared to the diadromous fish abundances in other coastal connecticut rivers, however, these numbers are small. And while the number of fishes caught was not great, the fact the over 50% of fishes captured by this study were diadromous species should be enough to warrant further investigation into building a fish passage at Wallace Dam. Two possible reasons for this smaller number are environmental degradation and sampling bias.