A Positive Assessment of the Status of the Delaware River American Shad Stock and its Fisheries

An assessment of the Delaware River American shad stock and its fisheries has just been concluded, producing a positive picture of the status of the stock. The assessment was conducted by a multi-state fish and wildlife cooperative organization focused on fishery resources of the Delaware River, the only undammed major river on the East Coast of the United States. American shad migrate up to 300 miles upriver from the mouth of Delaware Bay, into New York state waters. A critical question was whether the fisheries were having negative impacts on stock reproduction.  Young-of-year production has been monitored annually since 1980, using two beach seine surveys. There is a statistically significant positive trend in YOY catch-per-haul, stemming largely from low indices in the earliest years. Adult abundance was low in mid-century due to annual anoxia below Philadelphia. Anoxia disappeared by 1987, and adult catch-per-haul in a commercial haul seine fishery in the non-tidal River in New Jersey, with data back to 1925, shows the index was low during mid-century, then increased to peak levels in the 1980s and 1990s. Adult relative abundance declined in the 2000s, and has a highly significant negative correlation with relative abundance of striped bass in Delaware Bay and the tidal River since 1982. Plots of the young-of-year index as a function of the adult index show that reproductive output of this stock has been stable, even when adult run size declined to the lowest levels observed since 1980. This finding was a major influence on the assessment finding that the fishery level is sustainable.