Crime Scene Investigation: The Ecological Fingerprints of Anadromous River Herring

Anadromous River herring have experienced dramatic declines over the past decade. In North Carolina, current field collections methods for adult river herring including electrofishing have yielded catches of far too low for an adequate assessment of spawning. The spawning activity and spawning periodicity can be quite variable when population abundances are low thus decreasing the chances of locating spawning fish difficult. So even when spawning is sporadic and variable, spawning adults leave behind evidence “Ecological Fingerprints” in the form of eggs and larvae. We assessed spawning activity by the presence of larval river herring abundance in the coastal rivers of North Carolina from 1982 to 2012. Larval river herring abundance varies annually within rivers and also between rivers.  The Chowan River consistently produces the highest abundances of larval river herring (400 larvae/ 100m³). Chowan River has historically supported the largest commercial catches of adult river herring in North Carolina. The Tar River which produced River herring larvae in 2004 produced no spawning adults in 2012 and no larvae were collected from the river. Assessing river herring larvae as evidence of spawning offers a real advantage  for assessing river herring spawning habitat.