REPRODUCTION OF SHORTNOSE STURGEON IN THE GULF OF MAINE: A MODELING AND ACOUSTIC TELEMETRY ASSESSMENT

            The Penobscot River is the subject of an intensive river restoration project involving the removal of the two lowermost dams.  A third dam was previously removed; however, portions of the structure remain in the river.  This study investigated the extent of suitable spawning habitat for shortnose sturgeon downstream of the lowermost dam and the legacy effects of the Bangor Dam in relation to spawning migrations.  A two dimensional hydrodynamic model was created and analyzed for spawning habitat suitability and passage at the dam using River 2D version 0.95a.  Results indicate that suitable spawning habitat is present in the river reach accessible to shortnose sturgeon and they should be capable of passing the remnants of the Bangor Dam during spring river conditions.  Shortnose sturgeon (Acipenser brevirostrum) of the Penobscot River were also monitored using acoustic telemetry.  Telemetry results indicate a high rate of movement out of the Penobsoct and exchange between the Penobscot and Kennebec Rivers.  Most telemetered females with eggs in the late stage of development that overwintered in the Penobscot left the river system prior to suitable spawning conditions.  No upstream movements were detected during presumed favorable spawning conditions and 922 hours of sampling failed to capture shortnose sturgeon eggs or larvae in the Penobscot River.  Females with late stage eggs were later detected at known spawning areas in the Kennebec complex (Kennebec, Androscoggin, and Sheepscot Rivers).  These results indicate that currently the Penobscot is unlikely to host spawning and suggest a metapopulation or patchy population structure within the Gulf of Maine.