There was a time when every river town in the Hudson Valley was home to commercial shad fishermen. The appearance of their boats and nets on local shores was a certain sign spring had arrived. Tradition taught that the first run of American shad left the Atlantic to spawn in the river’s fresh water reaches when the forsythia were in bloom in late March – early April. Dogwoods signaled the middle of the run. The final run of shad, the largest of the fish, according to Hudson rivermen, occurred when the lilac flowered in mid-May.
In 2010, New York State halted commercial fishing of American shad because of collapsing populations in the river and on the coast. Shad spend most of their lives at sea following an isotherm of 13 to 18 degrees Celsius, moving south and north as the Atlantic waters warm and cool. They migrate up estuaries from the St. Johns in Florida to the St. John in New Brunswick and each in between. George Washington once had a commercial shad fishing operation on the Potomac.
No one reason has yet been identified for the collapse of the fishery. It is possible the blame is shared amongst many causes including: power plant cooling water intakes such as those at Indian Point; a coastal intercept fishery that captures the shad before they can migrate; and zebra mussels that rob the estuary of vital nutrients.
More on Hudson River fisheries here.