Shortnose sturgeon (Acipenser brevirostrum): Searching for spawning habitat in the Penobscot River, Maine

In 2006 shortnose sturgeon (Acipenser brevirostrum), a US endangered species, were rediscovered in the Penobscot River, Maine.  In the winters of 2007, 2008, and 2009 more than 50% of the acoustically tagged shortnose sturgeon in the Penobscot River remained in the upper estuary (October – April).  A preliminary estimate of the overwintering population is 701 individuals (95% CI: 445-1033).  In other river systems spawning has been documented over rubble, gravel, and ledge substrate during decreasing flows, as water temperatures increased from 9 to 18°C (Kynard 1997).  In 2008 and 2009, unsuccessful attempts were made to collect eggs and/or larvae during suitable river conditions.  Acoustic tracking and River 2D, a two dimensional bathymetric model, will be used to target sampling in spring 2010.  This, along with increased sampling effort using artificial substrates and modified ichthyoplankton nets will enhance efforts from 2008 and 2009.  Detailed habitat characteristics will be collected in the spawning area if eggs or larvae are captured.  Modeling, capture results and DIDSON images from the spring 2010 field season will be presented.  Assessing current and future spawning habitat is particularly important for the Penobscot population, due to its unusual life history and impending plans to restore historic sturgeon habitat.