Truck-and-Transport and Local Management on River Herring Population Run Size in Several New England Rivers

River herring populations in New England, both alewife and blueback herring, have suffered dramatic declines in annual adult run size in the last few decades.  There are several hypothesized reasons for the declines, including at-sea by-catch, predation via striped bass, and continued lack of suitable habitat because of a lack of adequate passage at dams to upstream spawning habitats.  New England has a diverse and disjunct management system for sustaining and augmenting river herring runs, and are often governed and managed at individual stream or river basin.  Because of the individual river population evaluation, there are few opportunities to assess management actions without environmental background confounding results.  In order to get a better understanding of effects of management activities, specifically truck and transport of adults into upstream spawning habitat and increased escapement, we compared contemporary trends of nine New England rivers (Connecticut, Merrimack, Lamprey, Cocheco, Oyster, Damariscotta, Orland, St. George and St. Croix) from Long Island Sound to Maine.  We conducted various regression modeling, including segmented regression, to estimate break points in temporal trends in the run-size data.  Importantly, this analysis incorporates 1) annual, 2) sporadic and 3) totally absent truck-and-transport activities and low to high harvest rates. The latitudinal breadth of this analysis ranges from high to moderate striped bass predation and potentially varying susceptibility to ocean by-catch.  While there appears to be very strong signals of regional trends, passage and truck-and-transport, appear to be important factors in the establishment and resilience of run size.