Habitat Use

Abstract

Radio telemetry was used to examine the habitat preferences of northern snakeheads between October 2006, and August 2007.  Radio transmitters were surgically implanted in 49 adult snakeheads.  These fish were located once per month from October to March, and twice per week from April to August.  For each location, the date, time, tide level and GPS coordinates were recorded.  Habitat data were also recorded, including depth, substrate type, turbidity, temperature, salinity and dissolved oxygen.  Finally, cover such as woody debris or aquatic vegetation was described.  For a subset of these locations, habitat was described for a paired random location to determine snakehead microhabitat preference.  Data are currently being analyzed, and results will be reported here and published in a scientific manuscript.  In winter, snakeheads remained in the open waters of the tidal embayments, associating with soft, silty substrates and the remaining macrophyte beds.  Fish were found in the deepest waters at this time of year, but were still rarely found in areas > 2 m deep.  In spring, fish moved to the inner parts of the bays and up the creeks.  Fish were strongly associated with cover, hiding under floating debris mats along the shoreline in early spring, and moving to dense spatterdock and hydrilla beds later in summer.  Snakeheads were often so far in the spatterdock beds that they could not be reached by boat.  At high tides, many fish moved into shallow flooded water along the shoreline, and were often found in < 30 cm of water.  Data will be analyzed for specific preferences for each habitat variable, and for changes in habitat preference with season.