Using Passive Sonic Receivers to Understand Habitat Utilization of Walleye in the Tributaries and Outlet of Onondaga Lake, Syracuse, NY

Onondaga Lake (Syracuse, NY) was historically considered an oligo-mesotrophic lake that supported a coldwater fishery, including whitefish and Atlantic salmon.  The coldwater fishery was eventually lost by the early 1900’s, following industrialization, urban expansion, and over-fishing.  The close proximity of Onondaga Lake to the city of Syracuse resulted in the more than a century of industrial and metropolitan pollution. By the mid 20^th century, the system was classified as hypereutrophic.  As a result, Onondaga Lake was considered one of the most polluted lakes in the country.  The lake was classified as a Superfund Site in 1994, most notably for mercury contamination.  Recently, however, the lake has shown signs of recovery, including record lows in phosphorus and ammonia, fewer days of hypolimnetic anoxia, and increased macrophyte and benthic macroinvertebrate diversity. 

Onondaga Lake supports a diverse warm water fishery that, in recent years, has increased to approximately 40 species, annually.  Of those species, walleye (Stizostedion vitreum) have been consistently captured in gill nets in relatively high numbers since 2005.  Walleye were the most abundant species captured in gill nets from 2008-2010 (2.0, 3.3., and 3.5 fish/hr, respectively).  Despite an increase in the walleye population, there do not appear to be any signs of reproduction occurring in the tributaries to Onondaga Lake. 

To better understand walleye movements and habitat utilization in the Onondaga Lake system, walleye (N=17) were implanted with sonic telemetry transmitters in May 2010 and tracked biweekly using active tracking methods.  Passive receivers were placed in two major tributaries, Onondaga Creek and Nine Mile Creek, and in the lake outlet in August 2010.  Thirteen walleye were detected in the outlet at least once between August and November.  The number of walleye detected in the outlet increased from four in August to eight in October and November.  The number of tag detections on the passive receiver was markedly higher in the fall (N=1200) than in the summer (N=205).  No tag detections were recorded on the passive receivers in Nine Mile Creek or Onondaga Creek.  Similarly, no walleye were found in either tributary during active tracking (May-November).  The reduced fishing pressure and abundant food source in Onondaga Lake appears to provide ideal refugia for walleye during most of the year.  However, preliminary results indicate that the tributaries to Onondaga Lake may be unsuitable for walleye reproduction, suggesting that they return to natal or more suitable spawning grounds.